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Horticulture Science
Lesson 6
Classifying Ornamental
Plants
Interest Approach
Ask students to list as many plants as they possibly can
in two or five minutes. (An interesting side activity is to
ask them to list as many animals as possible in one
minute. Notice that many more animals are listed on
most student papers.) Begin a discussion on what types
of plants were listed. Are they monocots or dicots,
deciduous or evergreen, annual or perennial?
(With the side activity, are they mammals,
birds, reptiles, amphibians, or fish?)
Interest Approach cont.
Why do students know more animals than plants? Why
are students better able to classify animals than plants?
Is it because of parents’ lack of plant knowledge or
weaknesses in the educational system? Go around the
room from student to student asking each to name one
plant with which he or she is familiar. Immediately
classify each plant as a fern, gymnosperm,
or angiosperm (and whether each
angiosperm is a monocot or a dicot).
After each student has had a turn,
allow the class to make observations
as to which types of plants are the
most familiar and common.
Student Learning Objectives
•Discuss the classification and
naming of plants.
•Distinguish the major groups of
plants.
•Contrast the classification of
plants by life cycle.
Terms
• angiosperms
• annuals
• biennials
• binomial nomenclature
• bryophytes
• conifer
• cotyledon
• cultivar
Terms
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deciduous
dicots
evergreen
ferns
genus
gymnosperms
herbaceous
monocots
Terms
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morphology
perennial
species
taxonomy
variety
vascular plants
How are plants classified and
named?
• The branch of biology that deals with identifying
and naming organisms is taxonomy.
• Plants are classified based on the similarities of
their characteristics.
• Plant taxonomists compare flowering patterns,
stem and leaf structures, life cycles, genetic
similarities, and many other characteristics in
determining which plants are the most closely
related.
• The study of the form or
shape of organisms or parts
of an organism is called
morphology.
How are plants classified and
named?
• Taxonomists use categories to group the
plants.
• The categories, from general to specific,
are: Kingdom, Division (Phylum), Class,
Order, Family, Genus, Species, Variety,
and Cultivar.
• All plants are in the Kingdom Plantae.
Vascular plants (plants with tissue
specialized for conducting materials) are in
the Division (Phylum) Tracheophyta.
How are plants classified and
named?
• Plants are named using a system called
binomial nomenclature.
• This classification system was developed
by Carolus Linnaeus and uses Latin
terms as scientific names for plants.
Carolus Linnaeus, the
'father of modern
taxonomy'
How are plants classified and
named?
• Even though each plant is given at least
seven names, it is commonly referred to
by two scientific names.
• The two names used for the scientific
names of plants are the Genus name,
which is always capitalized, and the
species name, which is always lower case
(e.g., Liriodendron tulipifera).
Common Names for Liriodendron
tulipifera: Tuliptree, Tulip
Magnolia, Tulip Poplar, Yellow
Poplar, Whitewood
How are plants classified and
named?
• The genus is a group of plants that are
very similar to each other.
• The species is a group of plants that are
so similar that they usually mate freely
with each other in the wild.
• Plants are also called by common names,
but those names are specific and are
based on language and geographic
location.
How are plants classified and
named?
• For instance, Liriodendron tulipifera is
known in the United States as the yellow
poplar, tulip poplar, tulip magnolia,
whitewood, and tulip tree.
• Although the tulip tree may be known by
many common names in the United
States, the plant is recognized as
Liriodendron tulipifera everywhere on
Earth.
How are plants classified and
named?
• Sometimes cultivated plants within a species
show a significant difference from other plants in
the species.
• These plants are called a variety. The difference
is inherited from the previous generation through
sexual reproduction.
• The variety is written in lower case, underlined or
italicized, and follows the specific epithet.
• A variety of Colorado spruce with bluish needles
is written as Picea pungens
var. glauca or
Picea pungens glauca.
How are plants classified and
named?
• Another group important to the horticulture
industry is cultivar.
• Cultivars have distinguishing characteristics
from the other plants in the species, but
cultivars do not transfer those
characteristics to offspring
through sexual reproduction.
• Cultivars are propagated by
selective hybridization or asexual
means.
• A cultivar of red maple is written
as follows: Acer rubrum, also known
as “October Glory.”
What are some ways that we can put
plants into groups?
• The plant kingdom has become
successful all over the Earth by adapting
to a wide variety of different conditions
and niches.
• The following are some of the major
plant groups.
What are some ways that we can put
plants into groups?
• Bryophytes are plants that are classified
in the Phylum Bryophyta.
• These are nonvascular plants such as
mosses and liverworts.
• They tend to live in damp places and are
very limited in size due to the lack of
conducting tissue.
What are some ways that we can put
plants into groups?
• Ferns are vascular plants that reproduce by
spores.
• Some people call them the amphibians of
the plant world because they are dependent
on water for their sperm to swim through
during reproduction.
• Ferns have no true leaves but have fronds,
which have a double purpose of food
production and spore formation.
• Fronds tend to unfold from the center
of the plant, causing the newest fronds
to be called “fiddlehead.”
What are some ways that we can put
plants into groups?
• Gymnosperms are plants that reproduce
with seeds that lay naked on scales.
• Most gymnosperms reproduce using a
structure called a cone.
• Any gymnosperm that reproduces by cone
is called a conifer.
• Examples include pines,
spruces, and cedars.
What are some ways that we can put
plants into groups?
• Conifer leaves are specialized to be
either needles or scales.
• Most conifers are evergreen, holding
leaves all year.
• But some are
deciduous,
dropping leaves
in the winter.
•An example is the
bald cypress.
What are some ways that we can put
plants into groups?
• Angiosperms are seed plants whose
seeds develop within a fruiting body.
• Angiosperms all reproduce by flowers,
although many flowers are very small
and not showy.
• So if any plant has flowers, it is in the
Angiosperm group.
• There are two types of Angiosperm.
What are some ways that we can put
plants into groups?
• Monocots are plants that have a single
cotyledon or seed piece.
• Monocots have flower parts in multiples
of three, parallel venation on their
leaves, stems with scattered vascular
bundles, and narrow leaves.
• Examples include grasses, sweet corn,
and lilies.
What are some ways that we can put
plants into groups?
• Dicots are plants with two cotyledons in
their seeds.
• They have flower parts in multiples of
four or five, netted veins, and stems that
are organized in a ring pattern.
• They have broad leaves and include
roses, petunias, and geraniums.
What are
some
ways that
we can
put plants
into
groups?
How are plants classified by life
cycle?
• Plants are often classified based on their
life cycles.
• Gymnosperms and angiosperms
reproduce by seed, of course, but there
are different strategies for passing on
that seed to future generations of plants.
How are plants classified by life
cycle?
• Plants that complete their life cycle
within one year or one growing season
are called annuals.
• Seeds of annuals germinate, produce
leaves and roots, flower, produce seed,
and then die, all in less than a year.
How are plants classified by life
cycle?
• Many of our crops and garden plants are
annuals.
• Corn, soybeans, rice, wheat, potatoes,
and tomatoes are examples of annual
food crops.
• Petunias, impatiens, marigolds, and
zinnias are examples of garden annuals.
• Many plants that are considered weeds
(i.e., ragweed, pigweed, lambsquarter,
and crabgrass) are annuals, too.
How are plants classified by life
cycle?
• Biennials are plants that normally
require two growing seasons to produce
flowers and seed before dying.
• In the first growing season, biennials
grow vegetatively.
• In the fall, they go dormant and rest
until the following spring.
• During the winter months, they receive a
required cold treatment.
How are plants classified by life
cycle?
• Growth is resumed in the spring of the
second season.
• The plants bolt, flower, produce seed,
and die.
• This group of plants is fewer in number
than the other two groups.
• Some examples include hollyhock, Sweet
William, parsley, beets, and carrots.
How are plants classified by life
cycle?
• Technically, a perennial is a plant that
has a life cycle of more than two growing
seasons.
• It may take perennial plants a few years
to many years to reach reproductive
maturity.
• Woody perennials may flower and
produce seeds every year for many
years.
• They may be woody like trees and
shrubs or herbaceous.
How are plants classified by life
cycle?
• The shoots of herbaceous perennials
typically die back to the ground each
winter.
• The roots and crowns of herbaceous
perennial plants survive and send up new
shoots in the spring.
• Strawberries and asparagus are
herbaceous perennials.
How are plants classified by life
cycle?
• Woody perennial plants produce secondary
growth that persists year after year.
• Secondary growth gives the plants the ability to
grow in girth and height.
• During the winter months, they go dormant.
• Plant growth resumes in the spring.
• Examples of woody perennial plants include
apples, maples, oaks, almonds, and oranges.
How are plants classified by life
cycle?
Review/Summary
•How are plants classified and
named?
•What are some ways that we can
put plants into groups?
•How are plants classified by life
cycle?