Plant Identification - Oregon State University

Plant Identification
Amy Jo Detweiler, Jan McNeilan, Gail
Gredler
Horticulture Department

List 6 reasons why plant
identification is important
1. use of foods &
medicine
2. plant
information
3. cultural
requirements
4. flower & fruit
habits
5. propagation
methods
6. common
disease and
insect
problems

History of Plant Nomenclature
(naming of organisms)
• Dates back to
200 B.C. to
China and
Egypt
• Greeks and
Romans
classified plants
into 4 groups
•herbs
• undershrubs
• shrubs
• trees

Listed plants using Latin terms,
e.g. carnation would be
Dianthus floribus solitariis squamis calycinis
subovatis brevissimis corollis crenatus

Another example:
Oriental ivy-leaved maple
Acer orientalis hederae folio

Binomial System of
Nomenclature
• system developed by Carl Von
Linne or Linnaeus in the 1700’s
used to methodically classify and
name the whole of the natural
world
• Species Plantarum (1753)
• system still in use today

Botanical nomenclature
• language is mainly Latin with
Greek and some other languages
• these are “dead languages” whose
words and meanings will likely
change little over time

The names of plants
• The scientific name for a
plant consists of two words:
1. Genus or generic name
2. specific epithet
e.g.Quercus rubra
species

Back to our example:
Acer orientalis hederae folio
under the binomial system would be…
Acer palmatum
or Japanese Maple

Carpinus caroliniana
• American
hornbeam
• water beech
• blue beech
• ironwood
• musclewood

Reasons not to use
common names
• Well known plants often have
more than one common name
• not universal
• two or more plants may have
the same common name
• many species, particularly rare
ones, do not have common
names

Nymphaea alba
European White Waterlily
• 15 English names
• 44 French names
• 105 German names
• 81 Dutch names
• 245 total common names

•By using the binomial system
of nomenclature, plant
names are the same in all
languages!
•Every plant has a “first and
last name” where the last
name is written first.

Binomial Nomenclature
clarifies plant i.d.
• Deodar
cedar
• Atlas cedar
• Cedrus
deodara
• Cedrus
atlantica

Plant Classification
• There are over 1 million
botanically different plants in
existence named by the binomial
system of nomenclature.
• Modified by the International
Congresses in Plant Taxonomy

• Kingdom
• Division
•Class
•Order
• Family
• Genus
•Species
Plant Classification
Gardeners use these 3

Which part of the plant is
used for classification?

Plant Classification
•Nearly all classifications
are based on the
sexual
parts of the fruit and the
flower.

Family
• a group of plants with similar
characteristics especially flowers, fruits,
and seeds, the reproductive structures
are used for distinction.
• The size of a family varies from 1 to
100+
e.g Ginkgoaceae has one
genus Ginkgo biloba
Rosaceae has 100 genera
(Malus, Spiraea, Rosa)

Genus(plural genera)
• a group of plants which is a
closely related, definable
group of plants exhibiting
similar characteristics
(flowers, fruit, stems,
leaves, or roots) and
genetic affinity

The genus is usually a noun,
capitalized and can serve to
describe one of the following:
• a plants appearance-Hemerocallis
(day and beauty)
• supposed medicinal qualities-
Pulmonaria (lungwort)
• resemblance to body parts-
Hepatica (liver)
• honors a person by using their
name – Kalmia (Peter Kalm)

Specific epithet
• the second word in a scientific
plant name, not capitalized and
usually an adjective used to
describe size, color, leaf shape,
growth habit, origin of the plant or
to commemorate a person.

The specific epithet can give us
hints plant about the plant:
• Cotoneaster horizontalis
• Coreopsis gigantea
• Clerodendrum thomsoniae
• Godetia grandiflora
• Cistus x purpureus
• Chionanthus virginicus

Species
• the basis of the binomial system of
nomenclature
• a difficult word to define, a
population of individuals within a
genus that are capable of
interbreeding freely with one
another

Writing plant names
correctly
• scientific names should always be
underlined or in italics
• the genus is capitalized, the
specific epithet is not
• the name is only complete if it is
followed by the name of the
person who first described or
named it

For example: Red Oak
Quercus rubra Linnaeus
or
Quercus rubra L.
Quercus rubra or Quercus rubra

Plant species can be
divided more specifically
into:
•a cultivar
•variety
•hybrid
•forma

Cultivar
• “Cultivated variety” or horticultural
variety
• plants within a species that have
been selected especially for a
particular characteristic and are
propagated, usually asexually to
continue this trait(growth habit,
flower, fruitless)

Cultivar names
written in plain text, capitalized and
set off by single quotes, e.g.
Viburnum opulus ‘Roseum’
Viburnum opulus cv. Roseum

Variety
• botanical or wild variety
• a group of plants intermediate
between species and forma and
usually associated with inheritable
differences. They are recognized
as distinct populations breeding
true to type

Variety names
• written in lowercase and italicized or
underlined
• e.g. Pinus contorta var. contorta
Shore Pine
• Pinus contorta var. latifolia
Lodgepole Pine

Hybrid
• two closely related but distinct
species will be interbreed to form a
hybrid
• are often sterile and produce no
seed or fruit

Hybrid names
• written in lowercase and italicized
or underlined
• an “x” is placed between the genus
and hybrid epithet
Platanus occidentalis crossed
with Platanus orientalis
Platanus x acerifolia

Plant name exercise
• What is the name of the plant that
produces maple syrup?
Sugar Maple

Genus Specific
epithet
1. Acer saccharum
Variety or
Cultivar
Common
Name
Sugar
Maple
2. Fraxinus pennsylvanica ‘Patmore’ Patmore
Green Ash
3. Gleditsia triacanthos var. inermis Thornless
Common
Honeylocust

Integrated Approach to
Plant Identification
• Visual inspection of plant
characteristics
• Photographic references
• Plant classification keys
• Expert advice

Collect information
about what you see:
Herbaceous, conifer, broadleaved
evergreen, deciduous?

Collect information
about what you see:
What is the overall form of the
plant?

Collect information about
what you see:
What are the characteristics of
individual plant parts?

Leaf type

Leaf type-simple leaf

Leaf type

Leaf type-pinnately
compound

Leaf type

Leaf type

Leaf type

Leaf type

Leaf type

Leaf type

Leaf Arrangement

Leaf Arrangement

Leaf Arrangement

Leaf Arrangement

Types of Venation

Types of Venation

Types of Venation

Types of Venation

Leaf margins

Stem
and Bud

Other i.d.features -
buds

Other i.d.features-
bark

Other i.d.features -
spines

Other i.d.features
-fruit

Other i.d.features - fruit

Other i.d.features –
flower & fruit

Conifer I.D.: Cones

Other i.d.features -
flowers

Using dichotomous keys to
A.
B.
BB.
C.
D.
DD.
CC.
AA.
E.
EE.
F.
FF.
G.
H.
identify plants
A dichotomous key
offers users a
choice between two
characters. By
making a series of
choices between
two characters, a
correct I.D. is
made.

An example for shoes
A. leather
B. velcro closures EZ
BB. shoe laces
C. colored leather
D. red Zippy
DD. blue Snazzy
CC. white leather
AA. canvas
E. velcro closures
EE. shoe laces
F. low top Keds
FF. high top Converse

Example of dichotomous key
A. Leaves needle-like
B. Needles clustered
C. 2-5 needles/cluster Pine
CC. >10 needles/cluster
BB. Needles not clustered
D. Pegs on twigs
E. Square, sharp needles Spruce
EE. Round, blunt needles Hemlock
DD. No pegs on twigs
F. Large pointed buds Douglas-fir
FF. Buds round, clustered True fir
AA. Leaves flattened and scale-like
G. All leaves short and sharp Giant Sequoia
GG. Some leaves not sharp

Needles are soft

• Needles longer
than ½”
• No pegs on
twigs

flower and fruit
• leaf edges not smooth
• leaf not thick and
leathery
• fruit is nutlike and dry

Landscape Plants Website
http://oregonstate.edu/dept/ldplants

More resources
•Manual of Woody Landscape Plants – Michael Dirr
•Dirr’s Hardy Trees and Shrubs – Michael Dirr
•Manual of Herbaceous Ornamental Plants – Steven
Still
•Trees to Know in Oregon – Edward C. Jensen, EC
1450

More resources
•The Shrub Identification Book – George Symonds
•The Tree Identification Book – George Symonds
•Trees of North America and Europe – Roger Phillips
•A-Z Encyclopedia of Garden Plants – Christopher
Brickell
•Sunset Western Garden Book