Download sexual and vegatative propogation

OBJECTIVES
The student will be able to…
• Explain differences
between vegetative
reproduction and
sexual reproduction
and the advantages
of each.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
OBJECTIVES
The student will be able to…
• Design a seed germination setup for growing seeds
indoors for later planting outdoors.
• Draw how a seed with damping off would look
and explain the cause.
• Describe the processes for hardening off and
transplanting for seedlings.
• Take a hardwood, semihardwood, and softwood
cutting from an outdoor plant.
• Take a tip, stem section, leaf bud, and leaf
cutting from an indoor plant.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
OBJECTIVES
The student will be able to…
• Identify suitable and unsuitable rooting media
and say why each one is such.
• Describe each of the parts of a commercial mist
system and the functioning of the system.
• Assemble the materials for air-layering an
overgrown foliage plant.
• Draw the processes of budding and grafting and
explain why each process is useful in horticulture.
• List five plant species that have been genetically
engineered and explain why they were altered.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
• Plants are reproduced, or propagated, either
sexually or vegetatively.
– Sexual propagation involves seeds that result from
the union of sperm and egg cells.
• Possible in almost all cultivated plants & used extensively.
– Vegetative propagation is based on using parts of
existing plants to generate new plants.
• These daughter plants will have traits identical to
those of the plants from which they were derived.
• Often faster than seed propagation.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
• Vegetative propagation results in clones, exact
duplicates of the parent plants.
– Essential for preservation of desirable characteristics
that could be lost in sexual reproduction.
• Such as fast growth or high yield.
• Seedlings may resemble the parent plant, but will
seldom be exactly like it.
– A result of genetic recombination of male/female genes.
• Gene mixing will result in offspring with a variety of traits.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
• Whether a plant is reproduced sexually or
vegetatively depends on many factors:
– Ease of germinating
the seed.
– The number of plants
to be grown.
– Importance of preserving
a trait possessed by a
parent plant.
Sometimes plants are reproduced
vegetatively to obtain a diseasefree offspring.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Seed Formation
• Seeds can be formed as a result of a plant…
– Fertilizing itself (self-pollination).
– Being fertilized by another plant (cross-pollination).
• Offspring resulting from cross-pollination are
called hybrids and carry traits of both parents.
– A seed package bearing the word hybrid indicates
the seeds are the result of special breeding.
• Selected hybrid seeds produce healthier, faster-growing
plants, a phenomenon called hybrid vigor.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Seed Formation
• Hybrid seed results from controlled crossing of two
groups of plants, of known genetic makeup.
– One designated the female line, the other the male line.
• Crossing two genetically pure lines can produce
seed with the best traits of both parents.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Seed Formation
• Seed saved from hybrid plants will not grow good
plants the following year.
– Only the original hybrid seed bears the desirable traits.
• Seeds included in fruit produced from hybrid seed
result from random cross- or self-pollination, and
will not produce the same superior plants
– In some cases they may have low viability or be
completely dead.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• Knowledge of genetics comes originally from work
done in the 1800s by Czech monk Gregor Mendel.
– He noted plant & animal offspring resemble their parents.
• His experiments lasted for many years, studying
many different plant traits, key among them…
–
–
–
–
Plant height.
Flower color and position on the plant.
Seed color and seed shape,
Pod color and shape.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• Mendel suspected that offspring characteristics are
dependent upon contributions from both parents.
– And specific characteristics from each parent are passed
on directly rather than being blended together.
• An offspring may look exactly like the female parent, even
though it is a product of both parents.
• This manifesting of the traits in a visible way is
called the phenotype of the offspring.
– As opposed to actual hereditary content of the
offspring, which is the genotype.
• These traits are in pairs in each parent, and
later came to be called genes
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• Genes were classified initially as “recessive” or
“dominant” depending on their ability to physically
manifest themselves (phenotype) in the offspring.
– It is now known relationships can exist between genes.
– Partial dominance exists in some genes
• Meaning it is not a winner-loser situation when they combine.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• Shown is an example of the most basic type of plant
breeding done by Mendel.
– Crossing a pea with a shrunken-shaped seed with one
with a full round seed.
Figure 5-1 Homozygous parents produce heterozygous offspring in the next generation (F1)
Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• In each case, the s represents the
recessive gene for seed shape
(shrunken-shaped seeds).
– And S for the dominant gene (full seeds).
It is customary to
write recessive genes
as a lowercase letter
and dominant genes
as a capital letter.
Figure 5-1 Homozygous parents produce heterozygous offspring in the next generation (F1)
Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• The basic cross involves a pea parent homozygous
for the gene of shrunken-seed shape.
– Meaning both of its genes are recessive “s,” expressed
as ss because each parent has the genes in pairs.
Figure 5-1 Homozygous parents produce heterozygous offspring in the next generation (F1)
Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• When combined, these would potentially yield, in a
pool of four offspring, in the first generation (the F1),
all “heterozygous” (Ss) offspring.
– That contain one gene from each parent.
Figure 5-1 Homozygous parents produce heterozygous offspring in the next generation (F1)
Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• All of the offspring will all have full seeds (the
phenotype).
– Though they contain the gene for shrunken seeds.
Figure 5-1 Homozygous parents produce heterozygous offspring in the next generation (F1)
Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• Shown here is what most likely would happen in
regard to seed shape if two of the first-generation
offspring were crossed.
– Yielding a second generation (F2) of four more offspring.
Figure 5-2 Crossing heterozygous offspring from the F1 generation yields both heterozygous and
homozygous offspring in the next generation (F2). Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• The genes recombine to give…
– Two heterozygous offspring (Ss and sS)
– Two homozygous offspring (SS and ss).
Figure 5-2 Crossing heterozygous offspring from the F1 generation yields both heterozygous and
homozygous offspring in the next generation (F2). Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Mendelian Genetics
• In regard to the phenotype (visual expression of the
genes), three offspring would have full seeds
because the S is dominant.
– One would have shrunken seeds.
Figure 5-2 Crossing heterozygous offspring from the F1 generation yields both heterozygous and
homozygous offspring in the next generation (F2). Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Techniques of Plant Breeding
• Amateur plant breeding is an interesting activity, but
it seldom yields very spectacular plants.
– Desirable characteristics are usually the result of luck.
• A few basic rules of genetics when breeding plants
will help ensure success.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Techniques of Plant Breeding
• The two plants to be crossed nearly must always
belong to the same genus & often the same species.
– Cultivars within a species will usually cross-pollinate.
• Only in rare instances do plants cross between genera.
• In nature, seeds from cross-pollination make up only
4% of all seeds produced.
– Because pollen-bearing anthers within a flower are close
to the female style, self-pollination is most likely.
• Plants that never self-pollinate are species that
produce male &female flowers on separate plants
– Holly and bittersweet, for example.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Techniques of Plant Breeding
• Self-pollination can be achieved by sealing a flower
in a paper bag just before it opens.
– The flower will open within the bag and, having no other
source of pollen, will self-pollinate.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Techniques of Plant Breeding
• For cross-pollination, flowers that are ready to open
should be selected from two parent plants.
– Petals & anthers of the female parent should be removed
with scissors, and the blossom enclosed in a paper bag.
– On the male parent, the
flower should be opened
by hand & a small paintbrush inserted to pick
up some of the pollen.
The pollen should then be
taken to the female parent,
brushed lightly over the
style & the bag replaced.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
Figure 5-3 Hand pollinating a vanilla
orchid, the source of natural vanilla.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Techniques of Plant Breeding
• In several days the pollen will germinate and grow
down through the style to the ovary where it will
fertilize the eggs, and the style will shrivel and fall.
– The bag can be removed and the flower tagged with the
names of the parents.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Techniques of Plant Breeding
• When seed is mature & ready for harvest, usually
the seed pod splits, or the fruit drops to the ground.
– The color of the mature seeds will darken as they ripen.
• Cleaning removes the ovary tissues that surround the seed.
– Dry fruits such as the pods of beans or fruits of many
trees usually split open when mature
• The seeds can be shelled out with the fingers.
– With fleshy fruits such as peach or squash, cut the fruit
apart, extract the seeds & dry several days on a paper
towel.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Techniques of Plant Breeding
• For general storage of vegetable & flower seeds, a
sealed container kept in the refrigerator is sufficient.
– Glass jars, plastic containers, and freezer bags are
all suitable, as they maintain constant humidity.
• The life span of seeds in storage varies from days
to years among species.
– Excess vegetable seeds are commonly stored for use
the following year.
• Even under ideal storage conditions, the longer the
seeds are stored, the fewer seeds will germinate.
– Seedlings that do emerge will be weaker.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Techniques of Plant Breeding
• When planting seed that has been stored, it is
advisable to do a germination test.
– Planting a specific number of seeds & counting resulting
seedlings to calculate the germination percentage.
• This will allow the grower to sow the seed more thickly
to compensate for a decreased germination rate.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEXUAL AND VEGATATIVE PROPOGATION
Commercial Seed Production
• Many flowers and vegetables are grown from seed
because it is the cheapest source of plant material.
– Vegetable seed varieties are chosen for shipability,
disease & herbicide resistance, ability to withstand
mechanical harvesting, size, color, taste.
– Flowers are selected for growth habit, size, flower
color, disease resistance, and other qualities.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Growing Outdoors
• Sowing seed outdoors is called direct seeding.
– Used for commercially grown vegetables, flowers & herbs.
• As well as in home gardening.
• It is important to choose the site carefully.
– Providing the correct amount of light for the species.
– It should also be well drained.
– Soil must be loose and crumble easily.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Growing Outdoors
• Seeds should be sown at the depth and spacing
recommended on the package.
– The general rule is that seeds should be planted
one and one-half times as deep as their diameter.
– Spacing between seeds can be estimated from the
mature size of the plant.
• Thicker sowing is permissible/recommended, with weaker
seedlings will be pulled out to achieve proper spacing.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Growing Outdoors
• Soil used to cover seeds should be free of even
small clods to enable the emerging shoots to
reach the soil surface easily.
– Rub the soil between the palms to pulverize it.
• Timing is important when planting seeds outdoors.
– If planted too early in spring, seeds will fail to germinate
or germinate slowly because of cold weather.
– If planted too late, they may not mature within the
growing season.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Growing Outdoors
• Adequate soil moisture during the germination and
establishment parts of a plant’s life is essential.
– Drying of the soil at these times will be fatal to seedlings.
• Seeds in moist soil don’t need immediate watering.
– They absorb moisture from the soil to start germination.
• In dry soil, watering will supply moisture, and settle
soil around the seed.
– So the emerging root will have immediate contact with
water & nutrients.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Growing Outdoors
• A liquid fertilizer starter solution can be applied to
seedlings after germination is complete.
– While not essential, research has shown starter fertilizer
will increase the growth rate of seedlings substantially.
• Seedlings are considered established after true
leaves appear, indicating the root system is
absorbing water and nutrients from the soil.
– And the plant no longer is dependent on carbohydrate
stored in the seed.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Growing Outdoors
• Timing is important when planting seeds outdoors.
– If planted too early in spring, seeds will fail to germinate
or germinate slowly because of cold weather.
– If planted too late, they may not mature within the
growing season.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Natural Reseeding of Outdoor Plants
• A number of cultivated plants produce seed that
germinates naturally the following season.
– Such as tomatoes, corn, and petunias.
• Seedlings that grow untended are called volunteers.
– Generally do not produce plants of the same quality
as the parents.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Seed Growing Indoors for Home Horticulture
• Vegetable, flowers & herb seedlings can be started
6 to 8 weeks ahead of when required for the garden.
– A container for raising seedlings need not be elaborate.
• With adequate drainage for excess water.
– For large numbers of seedlings, plastic,
Styrofoam®, or wood nursery flats can
be purchased.
Compressed peat moss disks that swell with
water and form a plantable container for one
seedling are also available in garden centers.
Figure 5-4 Compressed peat pots.
Courtesy of Pinetree Garden Seeds, Gloucester, Me.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Seed Growing Indoors for Home Horticulture
• The seeds are planted in a growing medium.
– It must be fast-draining and not prone to packing.
• Commercial potting soils sold for houseplants fit
these requirements & are convenient for seedlings.
– Pure garden soil should
not be used because it
packs when restricted
in a container, making
it unsuitable for growth.
Figure 5-5 A commercially produced seed-starting
system for homeowners. Courtesy A. M. Leonard Co.
A home seed-starting
unit can also be used.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Seed Growing Indoors for Home Horticulture
• Sterilization of growing medium is an important
precaution if outdoor soil is a part of the medium.
– It kills fungi in the medium that cause plant diseases.
• To sterilize the medium, dampen, place in a covered
baking dish, in an 160 - 180 deg F oven for 1 hour.
– After cooling, medium can be poured into a clean seeding
container and seeds planted immediately
– Keep excess medium in a sealed plastic bag to
prevent recontamination.
• Houseplant potting soil seldom requires any
further preparation.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Seed Growing Indoors for Home Horticulture
• Spacing between seeds can be close provided the
plants will be transplanted soon after they emerge.
• Water can be supplied by sprinkling or misting
whenever the growing medium begins to dry.
– An easy way is to water seeds after planting and
enclose the seed container in a clear plastic bag.
• The plastic prevents moisture from evaporating.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Seed Growing Indoors for Home Horticulture
• For most rapid germination, seeded containers
should be placed at a temperature of 70 - 80 deg F.
• A sunny area is not required for germination, and
should not be used for plastic covered/enclosed
containers.
– Heat from sunlight will build up and kill the seeds.
• Not essential for germination, bright light or direct
sunlight is needed after seedling emergence.
– Limited light entering a window is often not sufficient
to raise healthy transplants.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Seed Growing Indoors for Home Horticulture
• For raising most transplants, artificial light, a
greenhouse, or a greenhouse window is advisable.
If the seedlings become
pale and stringy instead
of compact, poor garden
plants will result.
Figure 5-6 Stringy tomato seedlings
raised in insufficient light. Photo by
Kirk Zirion.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Commercial Greenhouse Production of Seedlings
• Bedding plants are a commercial classification of
plants sold in spring, and in some climates in fall.
– Usually seedlings of annual flowers, vegetables, or
perennials.
• As a business they are worth $1.2 billion (wholesale)
annually in the United States.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Commercial Greenhouse Production of Seedlings
• Seedlings are sold in
several container types.
Four- or six-plant pony packs
or 4-inch diameter pots are
standard for retail sale.
Figure 5-7 A pony pack of geraniums.
Courtesy of National Garden Bureau.
For commercial growers selling to commercial
producers, plastic flats or plug flats (also known
as thermoform flats) composed of 100 to 800
small cells, each with one plant, are common.
Figure 5-8 A thermoform plug flat of seedlings.
Courtesy of Blackmore Co., Belleville, Mich.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Commercial Greenhouse Production of Seedlings
• The commercial system of production is highly
mechanized, and sometimes automated.
The trays are seeded
mechanically using a
commercial seeder,
& germinated in growth
rooms that precisely
control temperature.
Figure 5-9 A small-scale commercial seeder for plug
production. Courtesy of Blackmore Co., Belleville, Mich.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Commercial Greenhouse Production of Seedlings
• After germination, seedlings are moved to a greenhouse, or outdoors for several weeks.
– During which time they are irrigated and fertilized with
overhead irrigation systems.
• The seedlings are sold to commercial growers, who
transplant them directly to the field.
– Or commercial flower growers who transplant them into
containers such as pony or cell packs for further growing
and eventual retail sale.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Damping Off
• From emergence until several true leaves form,
seedlings are susceptible to damping-off disease.
– If a fungus is present in unsterilized growing media,
the organism rots the seedling stem.
Within a few days,
the plant collapses
and dies.
Figure 5-10 A damping-off infection in seedlings. Courtesy of Dr. R. E. Partyka, Columbus, Ohio.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GROWING PLANTS FROM SEED
Damping Off
• Once damping-off disease is detected, it can spread
rapidly and kill the majority of the seedlings.
– Fungicidal soil drenches are moderately effective in
stopping the spread.
• The best prevention is sterilizing the growing medium
before planting.
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By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
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GROWING PLANTS FROM SEED
Transplanting Seedlings at Home
• It is advisable to transplant seedlings to larger
containers as they begin to crowd each other.
– As leaves of plants overlap, less light will be available
to each seedling, and growth will slow accordingly.
• Competition of crowded roots for nutrients also causes stunting.
• Seedlings are very delicate, and transplanting must
be done carefully to avoid injury.
– Seedlings always should be picked up by a leaf rather
than by the stem, as injury to the stem will kill the seedling.
• Each plant should be watered to ensure contact
between the growing medium and the roots.
Practical Horticulture 7th edition
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GROWING PLANTS FROM SEED
Transplanting Seedlings at Home
• Seedlings should be kept in a shaded location for
2 to 3 days to minimize transpiration water loss
while the roots damaged during transplanting
resume water absorption.
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GROWING PLANTS FROM SEED
Hardening Off
• Seedlings raised in a controlled environment should
be subjected to a hardening-off period to acclimatize
them to outdoor conditions before transplanting.
– In suitable weather is suitable, the transplants should
be moved outdoors for several hours each day.
• After about a week, the transplants will be hardened
and will appear less succulent.
– Hardened plants are less likely to wilt or shock at
transplanting.
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GROWING PLANTS FROM SEED
Transplanting Outdoors
• If possible, an overcast day should be chosen for
transplanting outdoors to minimize wilting.
– If this is not possible, transplanting should be done late
in the afternoon to allow roots to recuperate overnight.
– Roots should be disturbed as little as possible and the
plant watered afterward.
• Some wilting should be expected, but if it is severe
or lasts more than 1 to 2 days, the plant will need
protection during reestablishment.
• The soil should be moist at all times so the roots
easily can replace water lost through transpiration.
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GROWING PLANTS FROM SPORES
• Of all the commonly cultivated plants, only one type,
ferns, bears spores.
In ferns, a spore drops
on the ground & grows
into a flat plant called a
prothallus.
The prothallus then
develops the sperm
and egg, which unite
and form the new plant.
Figure 5-11 Fern prothalli. From Wilson, Botany, 5/e. ©1971
Brooks/Cole, a part of Cengage Learning, Inc. By permission.
Practical Horticulture 7th edition
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GROWING PLANTS FROM SPORES
• Mature, healthy ferns develop hundreds of organs
called spore cases on the undersides of their fronds.
The spore cases resemble
small brown dots or lines,
and the cases protect and
release the spores.
Several months are
required for a fern to
develop & ripen spores.
When the spores are
mature, the spore cases
open and release the
spores into the air.
Figure 5-12 Spore cases on the underside
of a holly fern leaf. Photo by Rick Smith.
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GROWING PLANTS FROM SPORES
• To capture spores before they are released, test
the maturity of the spore cases by lightly tapping
the frond over a piece of white paper.
– When specks appear on the paper, the frond should be
cut off and enclosed in an envelope for several days.
• The spore cases then will open in the envelope, yielding
a tiny amount of spores in the bottom.
• Spores have the same growing requirements as
seeds: warmth, moisture, air & a growing medium.
• As they grow, prothalli should be misted daily, as
the egg and sperm they form can unite only in water.
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GROWING PLANTS FROM SPORES
• Eventually fronds will grow through the center
of the prothalli, which will die slowly.
– Young ferns then can be transplanted to individual
pots as soon as they are large enough to handle.
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VEGETATIVE PROPAGATION
• Propagating plants vegetatively involves use of nonsexual plant organs such as leaves, stems & roots.
– Vegetatively propagated plants almost always develop
identically to its parent.
• Preserves the work of plant breeders and natural mutations.
• Another reason to propagate vegetatively is to
reproduce plants that seldom flower or produce
only sterile flowers.
– Foliage plants and navel oranges fall into this group.
• A third reason is the relatively short time required by
vegetative propagation to produce a mature plant.
– A cutting can be rooted in as little as 2 weeks.
Practical Horticulture 7th edition
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VEGETATIVE PROPAGATION
Cuttings
• Cuttings are the most widespread vegetative
propagation method.
– Vegetative plant parts such as leaves, stems & roots
that regenerate missing parts to form new plants.
• They are cut from parent plants called stock plants.
• The environment required for growing cuttings is
the same as for germinating seeds: warmth,
moisture, and a growing medium.
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VEGETATIVE PROPAGATION
Cuttings
• Most parts used for vegetative propagation are
taken from above-ground portions of the plant,
and must regenerate roots.
– The growing medium will determine whether roots
will form, and their quality.
• The main requirement is to drain quickly to admit air
to the rooting area, yet retain some moisture.
– There is not one superior rooting medium.
• Many combinations of materials are used:
– Sand and part peat moss, part perlite, part vermiculite.
– Pure vermiculite, pure perlite, and pure sand.
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VEGETATIVE PROPAGATION
Cuttings
• Shrubs, vines, herbs, groundcovers, and a few
perennial flowers are propagated by cuttings taken
at different times of the year.
• Cuttings from woody outdoor plants are classified
by the degree of woodiness of the cutting.
– Hardwood, semihardwood, or softwood.
• A fourth classification, herbaceous, includes
cuttings from nonwoody plants such as many
groundcovers.
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VEGETATIVE PROPAGATION
Cuttings
• Hardwood cuttings should be taken in late fall
through early spring from the matured wood of
the past season’s growth.
They are generally
about 6 to 10 inches
(15 to 25 centimeters)
long and may come
from either deciduous
or evergreen plants
such as juniper,
viburnum, and apple.
Figure 5-13 Hardwood cuttings
of juniper (left), sycamore (middle),
boxwood (right). Photo by Kirk Zirion.
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VEGETATIVE PROPAGATION
Cuttings
• The specific procedures for rooting cuttings vary.
– Cuttings are generally cuttings are wrapped in plastic
and stored over winter in the refrigerator.
• Cuttings should be enclosed in a plastic bag to
prevent moisture loss & placed in a 70 - 80 deg F
location
– Roots should form in less than 6 weeks, and dormant
buds should begin growing shortly thereafter.
• Cuttings can be hardened off and transplanted several
weeks later.
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VEGETATIVE PROPAGATION
Cuttings
• Semihardwood cuttings are taken in summer from
the partially matured new growth of woody plants.
– Cuttings are made 3 to 6 inches long.
• Because they lose water through their leaves very
rapidly, cuttings should be placed in a pre-moistened
plastic bag as they are cut.
• The procedure for rooting is the same as for
hardwood cuttings.
– But rooting is often more rapid.
Practical Horticulture 7th edition
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VEGETATIVE PROPAGATION
Cuttings
• Softwood cuttings are taken in late spring from
succulent new growth produced that season.
– They generally root more consistently and quickly
than either hardwood or semihardwood cuttings.
• Picking the cuttings at the right stage of maturity is
crucial to success.
– Rapidly growing shoots are too tender & prone to rotting.
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VEGETATIVE PROPAGATION
Cuttings
• Ideally, the shoots should be slightly flexible but
should snap when bent to a 90 degree angle.
– They should be harvested into wet plastic bags and
rooted using the same directions as for hard- and
softwood cuttings.
• Because the younger parts of plants generally
root more easily than more mature parts, softwood
cuttings are the most reliable way to vegetatively
propagate most woody outdoor plants.
Practical Horticulture 7th edition
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VEGETATIVE PROPAGATION
Cuttings
• Herbaceous cuttings are equivalent of softwood
cuttings, but taken from herbaceous plants.
– Such as coleus and impatiens, that never become woody.
• Herbaceous cuttings can be taken and rooted at
any time during the growing season.
– Generally 2 to 4 inches long, taken from the tip of a stem.
• As with all the types of cuttings, bases should be
planted in damp rooting medium and the cuttings
enclosed in a plastic bag to increase humidity.
– Keeping cuttings wet from the time they are cut
until they are stuck in the medium will reduce wilting.
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VEGETATIVE PROPAGATION
Cuttings
• Root cuttings are sections of thickened roots without
leaves or stems attached.
– Only a few outdoor plants will grow from root cuttings.
• These species have the ability to generate an adventitious bud.
• Root cuttings of most outdoor plants are best taken
in early spring, just before new growth begins.
– Carbohydrate reserves are at a maximum, and the
plants are ready to emerge from dormancy.
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VEGETATIVE PROPAGATION
Cuttings
• Root cuttings should be protected from drying, and
can be harvested by digging out medium-sized roots
from around the base of an established plant.
– The sections can be cut into 3-inch (8-centimeter) lengths
and planted horizontally 1/2 inch deep in rooting medium.
Figure 5-15 Rooting stem tip (left),
stem section (middle) & leaf bud
(right) cuttings. Photo by Rick Smith.
Practical Horticulture 7th edition
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VEGETATIVE PROPAGATION
Cuttings
• Cuttings of indoor plants can
be of four types, depending
on the part of the plant from
which they are taken.
–
–
–
–
Stem tip cuttings.
Leaf Bud Cuttings.
Stem Section.
Leaf Cuttings.
Figure 5-14 A typical dicot plant, showing where stem tip, leaf bud,
and stem section cuttings would be found. Drawing by Bethany Layport.
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VEGETATIVE PROPAGATION
Cuttings
• Stem tip cuttings are the most
common type and consist of
the top 2 to 4 inches of a
growing stem.
The procedure for rooting the cuttings is
the same as for cuttings of outdoor plants.
Figure 5-14 A typical dicot plant, showing where stem tip, leaf bud,
and stem section cuttings would be found. Drawing by Bethany Layport.
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VEGETATIVE PROPAGATION
Cuttings
• Leaf bud cuttings are taken after
the stem tip has been used.
– Any plant propagated by stem
tip cuttings can be propagated
by leaf bud cuttings.
Each cutting includes a short section
of stem, one leaf & its corresponding
axillary bud.
When the base of the cutting roots, the
axillary bud breaks dormancy & forms
the new stem of the plant.
Figure 5-14 A typical dicot plant, showing where stem tip, leaf bud,
and stem section cuttings would be found. Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
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VEGETATIVE PROPAGATION
Cuttings
• Stem section or cane cuttings
are short pieces of thickened,
leafless stem.
After the top of the plant is removed
for a stem tip cutting, the remaining
stem is cut into pieces containing
two to three nodes each.
The sections are laid horizontally
half-buried in the rooting medium.
A plastic covering is not essential
provided the medium remains moist.
Figure 5-14 A typical dicot plant, showing where stem tip, leaf bud,
and stem section cuttings would be found. Drawing by Bethany Layport.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
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VEGETATIVE PROPAGATION
Cuttings
• Leaf cuttings contain a single leaf & sometimes its
petiole—propagation procedures vary by genera.
Most indoor plants cannot be
propagated using only a leaf.
Only certain species generate
buds where the leaf blade joins
the petiole or along leaf veins
or margins.
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VEGETATIVE PROPAGATION
Cuttings
• Leaves of African
violet & peperomia
are picked with the
petiole attached.
The leaf is buried in the
rooting medium up to the
blade, and new plants
form at the soil line.
Figure 5-16a African violet leaf cutting.
Image copyright © 2008. Paul Postuma
Ars Informatica. By permission.
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VEGETATIVE PROPAGATION
Cuttings
• Leaves of Bryophyllum and succulents such as jade
plant, burro tail & echeveria, are picked directly off
the plant & laid on the surface of the medium.
A medium largely composed of
sand is best; enclosing in
a plastic bag is not advisable.
Up to twenty new Bryophyllum
plants will form around the leaf
margin.
With others, single plants will
appear where the leaf was
broken from the plant.
Figure 5-16b Jade plant. Courtesy of Jim Mercer.
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VEGETATIVE PROPAGATION
Cuttings
• Fibrous-rooted begonias like rex begonia produce
new plants along the veins of mature leaves.
– And also where the petiole connects to the leaf blade.
• Whole leaves or pieces of leaves should be laid
on a damp rooting medium so veins make contact.
• Cutting veins with a knife stimulates bud formation,
and three to five cuts can be made on each leaf.
– A mature leaf can be cut crosswise in 1” long sections
and the base of each stuck in rooting medium.
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VEGETATIVE PROPAGATION
Cuttings
• Orientation of the cuttings is critical.
– The end of the section on top originally must be up, and
the part that was lower is planted in the rooting medium.
• Sections inserted upside down do not root.
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VEGETATIVE PROPAGATION
Cuttings
• After the leaf section roots, a new plant will be
produced at the base & grow up beside the leaf
section.
Figure 5-16 Leaf cuttings. (a) African violet. (b) Jade plant.
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VEGETATIVE PROPAGATION
Cuttings
• Propagation from leaf cuttings is slow.
– Generation of an adventitious bud and roots is an
energy-consuming process.
• Several months will be required before the young
plants are large enough to be transplanted.
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VEGETATIVE PROPAGATION
Cuttings
• Select cuttings from shoots without flowers or flower
buds, or if this is not possible, pick off the flowers.
– A cutting with blossoms will channel energy into the
reproductive parts, and be less likely or slower to root.
• Note positions of nodes on the stem of the cutting.
– Roots are often generated first at these sites, so cuttings
should be made with at least one node near the base.
• Leafy cuttings wilt easily and once severely wilted
are less likely to root.
– Cuttings should be kept moist after cutting & before
being stuck in the medium to slow water loss.
Practical Horticulture 7th edition
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© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
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VEGETATIVE PROPAGATION
Cuttings
• A humid chamber to minimize transpiration can be
made easily with a light translucent storage box.
Leafy cuttings wilt easily
and once severely wilted
are less likely to root.
Cuttings should be
kept moist after cutting
& before being stuck in
the medium to slow
water loss.
Figure 5-17 A rooting chamber made from a translucent storage box. Idea supplied by Janie Varley,
Vanderbilt, Tex. Photo by Jennifer Finney Janssen, M.Ed., Jackson County Extension Agent—Family
and Consumer Sciences, Texas AgriLife Extension Service.
Practical Horticulture 7th edition
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VEGETATIVE PROPAGATION
Cuttings
• Any leaves that will be covered after the cutting is
stuck into the rooting medium should be removed.
– Left on, they rot & provide a breeding ground for disease
organisms.
• Leaves that die and drop from the cuttings should
be removed, with whole cuttings that appear dead.
• A heat source at the bottom of the rooting chamber
where the roots will be forming will increase the
speed and success of rooting cuttings.
• Use of a rooting hormone can increase rooting
speed and success.
Practical Horticulture 7th edition
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VEGETATIVE PROPAGATION
Cuttings
• Gently tug the rooting cuttings about once per week
to determine whether rooting has occurred.
– If it slips out easily, no anchoring roots have formed.
• The cutting should be inspected for signs of rotting and,
if still healthy, can be reinserted in the medium.
– If the cutting does not pull out with gentle tugging, it has
roots already.
• The plastic lid can be opened partially to accustom
the plants to normal humidity, and removed entirely
after several days.
– After 1 week, cuttings can be transplanted to pots.
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VEGETATIVE PROPAGATION
Cuttings
• A few outdoor plants, such
as willow & pussy willow,
and many tropical indoor
plants can be rooted and
grown in water.
Stem tip cuttings are usually used,
with lower leaves removed & the
cutting absorbing water through
the cut end until roots are formed.
Practical Horticulture 7th edition
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VEGETATIVE PROPAGATION
Commercial Rooting of Cuttings
• A greenhouse generally has one or more benches
exclusively used for propagation and equipped with
an intermittent mist system.
This system is
designed to keep
transpiration at a
minimum until the
cuttings regenerate
roots and can take
up water & nutrients.
Figure 5-18 A mist nozzle. Photo courtesy of CEV Multimedia, Ltd., Lubbock, Tex.
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VEGETATIVE PROPAGATION
Commercial Rooting of Cuttings
• The interval of time between mistings will depend
on the rate of evaporation in the greenhouse.
– The goal is to remist just before the leaves are fully dry.
• But not to wet them excessively, as excessive wetting
leaches nutrients from the leaves and increase
occurrence of disease infection.
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VEGETATIVE PROPAGATION
Commercial Rooting of Cuttings
• The intermittent mist system consists of a time clock
that times the interval of misting, an electric solenoid
valve that turns the mist on and off, and piping and
mist nozzles over the plants.
In some cases an electronic
leaf can be substituted for
a time clock.
This is a small metal
sensing plate attached
to an unit that controls
the solenoid valve.
Figure 5-19 A Mist-A-Matic to
control a mist system. Photo
courtesy of Griffin Greenhouse
& Nursery Supplies.
Practical Horticulture 7th edition
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© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
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VEGETATIVE PROPAGATION
Commercial Rooting of Cuttings
• A root-zone heating system is often also used to
warm only the bases of the cuttings to encourage
faster and more reliable rooting of cuttings.
Figure 5-20 A Heat-A-Matic
suitable for use with pots or flats.
Courtesy of Griffin Greenhouse
& Nursery Supplies.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
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VEGETATIVE PROPAGATION
Crown Division
• Crown division is probably the most common and
reliable home propagation method.
Used for herbaceous perennials,
shrubs, & houseplants such as
ferns, asparagus ferns, African
violets, and spider plants.
One plant is separated into
two or more pieces, each
with a portion of roots & crown.
Figure 5-21 Division of a plantain lily into several smaller crowns. Photo by George Taloumis.
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VEGETATIVE PROPAGATION
Crown Division
• Shrubs to be divided must be multi-stemmed.
• Division can be done any time in the growing season.
– Plants in active growth must be treated carefully to
minimize water loss through the leaves.
• They should be divided when dormant if possible.
– By cutting through the crown with a spade so that it is
broken down into several sections.
• A part of the parent crown can be left to rejuvenate
the shrub.
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VEGETATIVE PROPAGATION
Crown Division
• With herbaceous perennials, the entire plant is dug
up and cut apart.
– The sections are then replanted and watered.
• When dividing houseplants, the parent is removed
from its pot, cut or pulled apart & sections repotted.
– Pruning is normally unnecessary.
• If wilting occurs, the newly potted sections can be
left in plastic bags under indirect or filtered light for
several weeks until the roots are reestablished.
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VEGETATIVE PROPAGATION
Layering
• Layering is another home method for propagating
vines and shrubs with a trailing growth habit or
flexible branches.
– A low, flexible shoot is bent to the ground when the
plant is in active growth.
• It is held in place by a bent wire or heavy stone, and
mounded with soil a short distance back from the tip.
– Within a few months, roots should have formed on the
covered portion of stem, and the layer can be cut from
the parent plant and transplanted.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Air Layering
• Air layering is a technique
used primarily on large
houseplants such as
rubber plants.
– It involves inducing stem
rooting of a plant that still
has its own root system.
Used to obtain new plants from
a large branched specimen, to
shorten a plant that has grown
too tall, or make a plant which
has become tall and leafless
short and bushy again.
Figure 5-22 Air layer. Photo by the author.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Air Layering
• Choose where the new
root system is desired…
– A 1” wide strip of bark
should be cut around the
stem & the bark pulled off.
Girdling removes the phloem
& cambium but not the xylem,
which still translocates water
to the top of the plant.
– Place a handful or two
of damp sphagnum
moss over the girdled
area & wrap with plastic.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
Figure 5-22 Air layer. Photo by the author.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Air Layering
– Use twist-ties or tape to
secure both ends and
seal in moisture.
– Place foil over the plastic
if the air layer area will be
exposed to direct sunlight.
• To prevent overheating.
– In 2 to 3 months, when
several roots with lengths
of 2” to 3” have formed,
the air layer can be cut
and transplanted to its
own pot.
Figure 5-22 Air layer. Photo by the author.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Runners, Rhizomes, and Stolons
• Runners, Rhizomes, and Stolons are horizontal
stems produced as a natural means of vegetative
reproduction.
– Runners grow above-ground.
• Strawberries, ferns, spider plants, and strawberry begonias.
– Rhizomes & stolons grow at ground level or below-ground.
• Typically found on bamboo, grasses, and some irises.
• There are subtle botanical differences among them,
but they are handled much the same in propagation.
– As modified stems, these organs have buds, nodes,
and internodes.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Runners, Rhizomes, and Stolons
• Runners are found on such plants as strawberries,
ferns, spider plants, and strawberry begonias.
Figure 5-23 Rooting a runner of
a spider plant. Photo by Kirk Zirion.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Runners, Rhizomes, and Stolons
• A runner will have only one bud at the tip, whereas
stolons and rhizomes may have several.
– The nodes are the sites where new plants will form.
• With a runner on an outdoor plant, the stem can be
positioned as it begins to form the new plant.
– The runner will root without additional attention and can
be severed from the parent and moved after rooting.
• As houseplants are grown in pots, runner plants
may never make contact with a rooting medium
without help and can live attached to the parent
indefinitely.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Runners, Rhizomes, and Stolons
• When a new plant is wanted, a small pot of growing
medium can be placed under the runner plant.
– Roots will form in less than a month & the runner detached.
• When this method is impractical, the runner can be
detached & treated as an unrooted stem tip cutting.
• Propagating plants from rhizomes and stolons is
done much the same way.
– The stem connecting the young plant to its parent
is cut after a moderate amount of roots has formed.
• The young plant is then transplanted to the new location.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Suckers and Offsets
• Suckers and offsets are young
shoots that grow from the roots
or stems of mature plants.
Functionally similar to rhizomes and
stolons, and found in many shrubs &
houseplants such as bromeliads,
succulents, and cacti.
Figure 5-24 A snake plant with two
young offsets. Photo by Kirk Zirion.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Suckers and Offsets
• Offsets on cacti are frequently
produced on top of the plant
and can be broken off and
rooted without difficulty.
• Suckers from the bases of
plants may or may not have
developed root systems
independent from the parent.
– If so, they can be transplanted
directly.
– If not, they are treated as
cuttings.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
Figure 5-25 A pincushion cactus
with offsets. Photo by Rick Smith.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Storage Organs: Bulbs, Corms, and Tubers
• Underground storage organs are produced by some
herbaceous perennials.
– A repository of stored carbohydrate, botanically, these
are modified stems with nodes, buds & modified leaves.
• Lilies, gladiolas, and amaryllis.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Storage Organs: Bulbs, Corms, and Tubers
• Their natural means of vegetative reproduction is
the formation of clones of themselves (called bulbils,
cormels, or tubers) around the base of the parent.
– These can be broken off and planted in new locations.
• Preferably while the plant is dormant.
Blooming of storage organs
may take 2 to 3 years after
the year they are produced
because a minimum size
must be reached before
flowering will occur.
Figure 5-26 Removing a daughter bulb from the mother.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Grafting and Budding
• Grafting and budding are fairly complex methods of
propagation used for reproducing valuable fruit and
ornamental cultivars in nurseries.
– Budding & grafting unite genetically different plants so
they heal together & function as a single plant.
• An amateur who wishes to try should plan ahead and
consult reference books for more in-depth information.
• Budding transfers a bud of one plant to another
plant that will function as the root system, whereas
grafting attaches a small branch to another plant.
– Most frequently combining two cultivars of a species
into one plant that exhibits the best features of each.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Grafting and Budding
• Grafting can also serve other purposes:
– Repair of girdled trees that would otherwise die.
– Creation of unusual plant forms such as tree roses or
trees with weeping heads atop strong, straight trunks.
– Changeover of old orchard fruit trees to a new cultivar.
• Grafting & budding rely on activity of cambium cells.
– Must be done when the cells are dividing actively
and will heal the grafted area quickly.
• To determine the correct stage for grafting, bark
is examined for slippage.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Grafting and Budding
• Rootstock diameter must be equal to or larger than
that of the scion.
– Scion wood is usually a pencil thickness or slightly larger.
• Cambium of the stock & scion must be in contact,
preferably over as great an area as possible.
– If contact isn’t made, the graft won’t heal & the scion dies.
• The stock and scion must fit tightly together, and
the joint must be protected from drying.
– A tight graft union is achieved by wrapping the area
with special rubber ties or waxed string.
• Drying is prevented by a coating of wax.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Grafting and Budding
• Basic steps involved in a style called whip grafting.
Stock & scion cut to
equal size and ready
for grafting.
Figure 5-27a Steps in performing a whip graft. Courtesy CEV Multimedia, Ltd., Lubbock, Tx.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Grafting and Budding
• Basic steps involved in a style called whip grafting.
Stock & scion joined
and held together
with a rubber strip.
Figure 5-27b Steps in performing a whip graft. Courtesy CEV Multimedia, Ltd., Lubbock, Tx.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Grafting and Budding
• Budding involves removing a patch of bark with a
bud from a scion and laying it directly against the
cambium of the stock.
– Less risky than grafting
because the stock is
damaged only slightly
if the union doesn’t heal.
As with grafting, the
area of the union must
be protected from drying
with rubber ties.
Figure 5-28 Bud patches to be used in budding (upper) and a bud patch in place on a
branch (lower). Photo courtesy of Dr. Robert F. Carlson.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Tissue Culture
• Tissue culture, also called micropropagation, is
the propagation of plants from nearly microscopic
portions of parent plants.
Importance of propagation
from virus- free parent stock
has come to be appreciated
recently as the detrimental
effects of unrecognized
virus infection have
become known.
Figure 5-29 Tissue-cultured strawberries. Photo courtesy of Barbara M. Reed, National Clonal
Germplasm Repository, Corvallis, Ore.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Tissue Culture
• The technique has two distinct advantages over
traditional propagation:
– It enables mass production of a cultivar from an extremely
limited amount of parent stock, in a relatively small area.
– It enables the propagator to eliminate disease-causing
viruses from the parent material, unattainable through the
use of pesticides.
• And to propagate numerous virus-free offspring that
are healthy and vigorous.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VEGETATIVE PROPAGATION
Tissue Culture
• Tissue culture is not an amateur activity, because it
is nearly impossible to achieve the sterile conditions
necessary.
• Tissue-cultured plants still in test tubes are sold in
nurseries occasionally as novelty items.
– Particularly orchids, which were the main plants tissue
cultured for many years.
• The test tube is left sealed and treated as a miniature terrarium.
• When the plant outgrows the tube it sometimes
can be transplanted to a pot, though the
process is not always successful.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
GENETIC ENGINEERING
• Genetic engineering can harness the biological
machinery of bacteria and viruses to…
–
–
–
–
Manufacture otherwise hard-to-obtain plant products.
Combat genetically caused diseases.
Improve tolerance of plants to adverses.
Attain other similar commendable goals.
• For plant improvement, it changes the genetic
makeup of plants, without breeding or selection.
• Its main advantage is that it makes possible the
transfer of genes between completely unrelated
plants or bacteria.
– In rare cases, even from animals to plants.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
COMMERCIAL APPLICATION OF GENETIC
ENGINEERING
• In commercial horticultural production, research has
centered mainly on vegetable and fruit crop genetic
engineering.
– With a limited amount on flowers and other crops.
• Although genetically engineered crops are in
widespread cultivation, most are not horticultural.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
COMMERCIAL APPLICATION OF GENETIC
ENGINEERING
• Generally, genetic engineering of horticultural crops
has focused on
– Imparting disease and pest resistance.
– Imparting resistance to herbicides.
– Extending the length of product shelf life.
– Altering color.
• In flowers.
– Imparting cold-temperature resistance.
• In strawberries and eucalyptus trees.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
COMMERCIAL APPLICATION OF GENETIC
ENGINEERING
• One of the best known genetically engineered
horticultural crops is the ‘Flavr Savr’ tomato.
– Engineered to retain a firm texture longer than normal.
• Tomatoes destined for fresh eating must be handharvested to prevent bruising.
– Unlike canning tomatoes that can be harvested
mechanically—a less expensive process.
• Fresh tomatoes must also be transported quickly
and with careful packaging.
– To ensure that they arrive at the supermarket in an
attractive condition, appealing to the buyer.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
COMMERCIAL APPLICATION OF GENETIC
ENGINEERING
• The ‘Flavr Savr’ inhibits expression of the genetic
material that causes fruit to soften when it ripens.
– The softening part of ripening is slowed, although the
flavor continues to develop.
• This allows mechanical harvesting, increased
transport time, and longer fresh shelf life in the
supermarket.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
COMMERCIAL APPLICATION OF GENETIC
ENGINEERING
• A second genetically engineered crop receiving
widespread attention is a Thompson Seedless
grape variety engineered to be virus resistant.
– One of the most commonly cultivated table grapes.
• Also a component of blended wines.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
COMMERCIAL APPLICATION OF GENETIC
ENGINEERING
• Scientists hope that genetically engineered virus
resistance will reduce the expense of chemicals,
and their entry into the environment.
– Because it will no longer
be necessary to spray to
prevent the disease.
At present, only papaya &
squash have been engineered
successfully for virus resistance
and put into field production.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
COMMERCIAL APPLICATION OF GENETIC
ENGINEERING
• Some opponents of genetic engineering fear it
could upset the ecosystem in unknown ways.
– They feel that the accelerated pace of genetic change
could inundate the environment with bizarre plants,
causing an unstable ecological situation.
• Some organic farmers fear a biological pesticide,
which they use to control infestations of worms, will
no longer be effective due to insect resistance as a
result of widespread incorporation in many crops.
– Bacillus thuringiensis, is the source of genetic
material put into plants to cause their cells to
produce an insect poison.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
COMMERCIAL APPLICATION OF GENETIC
ENGINEERING
• The Environmental Protection Agency (EPA) has
approved a number of genetically engineered plants.
– Over 3 million acres of genetically engineered corn,
cotton, and potatoes were planted in the U.S. in 1997.
• A class-action suit has been filed against the EPA by
thirty-one groups who charge that the EPA has been
negligent in its approval of genetically engineered
crops.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
END OF
CHAPTER
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458