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Classifying Ornamental
Plants
Suppose you were walking through the
woods and stumbled upon an unusual
plant. What would you call it? Would
you know how to classify it? Could
you identify its characteristics? These
are questions many taxonomists
ponder when labeling a new plant.
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Take a couple of minutes and list as many
plants as you possibly can. Let’s classify
them as deciduous (loose their leaves) or
coniferous (remain as evergreens).
Now list as many animals as you can. Can
you classify them as birds, reptiles,
amphibians, insects, fish, or mammals?
Why do you know more about animals?
Student Learning Objectives
1. Describe the system used for
naming and classifying plants
 2. Identify the major groups of plants
 3. Describe the differences between
annuals, biennials and perennials
 4. Understand how this information is
important to the Horticultural industry
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Terms to Know
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Angiosperm
Annuals
Biennials
Binomial nomenclature
Bryophytes
Conifer
Cotyledons
Deciduous
Dicots
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Evergreen
Ferns
Genus
Gymnosperms
Herbaceous
Monocots
Perennials
Species
Woody
How Are Plants Named and
Classified?
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Plants are classified by the similarities
of their characteristics.
– Taxonomists compare flower patterns,
stem and leaf structures, life cycles,
genetic similarities and many other
characteristics.
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They are then grouped in specific
categories, or taxas:
Categories/Taxas
Example*
Kingdom
Plantae
Phylum (Division)
Class
Magnoliophyta
Liliopsida
Order
Cyperales
Family
Poaceae
Genus
Species
Triticum
aestivum
*Sample classification of bread wheat
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Botanists call plants by their last two
taxas – genus and species
– This system is known as binomial
nomenclature (two-word naming system)
– Developed by Carl Linnaeus
– Uses Latin for three reasons:
 Universal
(known by all scientists)
 Very descriptive
 Unchanged (contains no slang words)
– Genus is capitalized; Species lower case
 Ex.
Triticum aestivum
Cultivars
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In the Horticulture
industry, we usually
use cultivar names
as well. Ex;
Malus domestica
‘Fuji’
Picea pungens
‘Procumbens'
What Are Some Ways That We
Can Put Plants Into Groups?
Plants live in a variety of climates and
niches
 The adaptations that plants have made
to survive in different climates allows
for them to be classified into one of
four major groups:
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– Bryophytes, Ferns, Gymnosperms and
Angiosperms
Bryophytes
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Belong to the phylum
Bryophyta
Non-vascular plants
Liverwort
– No conducting tissues
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Live in damp places
Limited in size due to
lack of conducting
tissue
Ex. Mosses and
liverworts
Moss
Courtesy of Wm. C. Brown Publishers
Ferns
Ferns in the
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forest
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Fiddleheads
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Spores on
underside of
frond
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Vascular plants
Reproduce by
spores
Have no true
leaves; 0nly fronds
Fronds produce
food and spores
New fronds called
fiddleheads
Courtesy of Wm. C. Brown Publishers
Gymnosperms
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Reproduce with seeds
found in cones
Also known as a conifer
Leaves reduced to scales or
needles
Most are evergreen – hold
on to their green color year
round
– Ex. Pines, spruce, cedar
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Some can be deciduouslose their leaves
– Ex. Ginkgo, larch
Coniferous
evergreen –
Pinus
contorta
Deciduous
conifer –
Ginkgo
biloba
Courtesy of Wm. C. Brown Publishers
Angiosperms
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Plants that reproduce by flowers
There are two types: monocotyledons
(monocots) & dicotyledons (dicots)
A cotyledon is a food storage structure in
the seed.
– Monocots have a single cotyledon
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Ex. Grasses, corn and lilies
– Dicots have two cotyledons
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Ex. Roses, petunias and geraniums, beans
Angiosperms - Monocot
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Have flower parts
(sepals, petals, stamens,
pistils) in multiples of
three
– 3, 6, 9…
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Orchid – Paphiopedilum curtisii 
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Courtesy of Wm. C. Brown Publishers
Parallel venation
within the leaves
Stems with scattered
vascular bundles
Narrow leaves
Fibrous root system
Angiosperms - Dicot
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Flower parts are in
multiples of 4’s or
5’s
– 4,12,16 or 5, 10, 15
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Netted veins
Vascular bundles
are in rings around
the stem
Have broad leaves
Taproot system
Hibiscus sp.
Courtesy of Wm. C. Brown Publishers
Monocot vs. Dicot
Courtesy of Wm. C. Brown Publishers
Monocot vs. Dicot
Why is distinguishing between
monocots and dicots important in
landscape maintenance?
Stem Cross Section
What Is the Difference Between
Annuals, Biennials and
Perennials?
Plants are often classified based on
their life cycles
 Even though gymnosperms and
angiosperms reproduce by seed, there
are different strategies for passing the
seeds on to future generations
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Annuals
Corn – Zea mays
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Plants grow from seed,
flower, produce new
seeds all in one
season
It dies after producing
new seeds
Have an herbaceous
stem – green & fleshy
– Ex. Impatiens, corn,
snapdragons
See life cycle
Courtesy of Wm. C. Brown Publishers
Biennials
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Foxglove – Digitals purpurea
Plants that live for
two years, then
flower and die
Food is produced
during the first year,
flowers the second
year
– Ex. Foxglove,
carrot, queen
Anne’s lace
See life cycle
Courtesy of Wm. C. Brown Publishers
Perennials
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Bristlecone pine – Pinus
longaeva
Plants that live for
three or more years
Flower for a short time
Do not die after
flowering
Can be herbaceous or
woody – having thick
stems made of wood
– Ex. Tulips, Kentucky
bluegrass, trees and
shrubs
See life cycle
Back to Annuals
Germination----Growth---Flowering----Death
Back to Perennials
Germination---- Growth---Flowering----Dormancy
One or more flowering cycles
Back to Biennials
Germination---Growth---Dormancy---Growth---Flowering---Death
Season 1
Season 2
Courtesy of Interstate Publishing
Summary
What is the difference between an
angiosperm and a gymnosperm?
 How is a monocot different from a
dicot?
 Are evergreens herbaceous or woody
plants?
 How would you classify the grass
found outside on the lawn?
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Summary Cont.
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What makes up the scientific name of a
plant?
Why are scientific names written in Latin?
In what group would you find mosses?
Describe their habitat.
Describe the life cycle of a perennial.
Name all 7 taxas in the classification
system.
Summary Cont.
Can I spray Weed-b-gon on a lawn?
 Can I spray Grass-b-gon on day lilies?
 Could I spray Weed-b-gon on my
vegetable garden?
 What is the downside to including
biennials in a perennial flower garden?
 What are some practical classifications
I might want to give landscape plants?
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