The Nine Categories
The following 9 categories should be used together to identify a plant. In almost all cases, plants cannot be identify by one category.
Woodiness
Trees have trunks, branches, and sticks that are made of wood. The newest growth of a tree is usually green stems.
Shrubs also have trunks and branches that are made of wood with new growth appearing as green stems.
Herbaceous plants are plants that lack wood. They are typically annual in climates where winter sees freezing temperatures. Many herbaceous perennials will "die back" in the winter but the parts of the plant in the soil survive each year.
Arrangement
Do leaves or twigs "alternate" on the branch?
Or do they grow in pairs - opposite of one another?
Are there more than two leaves per node?
What is the angle between each layer of leaves?
The most common arrangements for leaves and twigs is opposite. Opposite leaves are paired at a node. Only Maples, Ashes, Dogwoods (MADog), Buckeyes, and shrubs in Caprifoliaceae are opposite in Indiana.
Alternate leaves do not grow in pairs.
Leaves may also be whorled. When 3 or more leaves are share a node, they are whorled.
If the leaves are all at the base of the plant, they are considered a basal rosette.
The angle between consecutive leaves can also be important. If they are 90°, shaped like they are decussate, if they are 180° they are
distichous, and between 45 and 180° is spiral.
3. Location or Habitat
Where is the plant located in the environment? Is it natural or planted? Is it wet or dry?
Is it on top of a hill, on the slope, or at the bottom? Is it rocky, sandy, clayey, or
disturbed?
Many species have limited ranges that they live in, which can be helpful for ID. Silver
maples naturally like wet spots in valleys but can also be planted in yards. Post Oaks
only like dry, rocky soils on top of hills.
4. Structure
a. Veins
Are the veins parallel or not? Do they reach the leaf margin? Do they start at the leaf
base and do the large veins attach to the minor veins?
Monocots, like grasses and lilies, have parallel veins while dicots have netted veins.
2
b. Branching pattern
Is the plant rounded/ovular, V-shaped, or pyramidal? Is it irregular?
Trees can sometimes be IDed far away using this strategy. Oaks are more V-shaped or
layered, maples are rounded, and sycamores are irregular.
c. Fibrous v taproot
Is the root one large “carrot-like” root or many small fibers? Is there a storage organ or
horizontal roots? Are there many root hairs?
Monocots and the carrot family usually have one large root while dicots will have more
fibrous systems. Many species store sugars in large roots, such as potato tubers or
daffodil bulbs. Plants use stolons or rhizomes to clone themselves, these generally do
not have many root hairs.
5. Leaves
a. Structure
Are the leaves compound or simple? Are they singly compound, doubly, or more? Do
they have a set number of leaflets? Is there a single end leaflet or a pair?
Walnuts are singly compound with an irregular number of leaflets and single end leaflet.
Locust is doubly compound with a paired end leaflet. Buckeyes are singly compound
with five leaflets attached to a single point (palmately compound).
b. Attachment
Do the leaves have long or short petioles? Are there stipules or a sheath present?
An example of long petiolate leaves is red oak. Short petiolate leaves include clasping
leaves (Solomon’s seal), sessile leaves (goldenrod), and sheathing leaves (many
grasses). Tulips and sycamores have stipules where the leaf meets the node.
c. Shape
Are the leaves symmetrical? Do they have the same shape throughout the plant? Are
the leaf margins smooth or serrated or lobed? Are there bristles present? What shape
would you describe the leaf as?
Elms are asymmetrical at the base of the leaf. Sassafras and mulberry shift their shape
over the season. Tulip is smooth, coneflower is serrated, and oaks are lobed. Red oaks
have bristles at the tips of their leaves. See the leaf shape chart below.
d. Hairiness
Are the leaves smooth or hairy? Are the hairs long and visible or short? Are they white
or black? Is the hair everywhere or limited to the top, bottom, veins, petioles, or twigs?
6. Flowers
What color are the flowers? Do they flowers have bilateral symmetry, radial symmetry,
or are they asymmetrical? Are they imperfect or perfect? What kind of inflorescence is
present? How is the peduncle attached?
3
Flower color is often the same throughout a family, like yellow in Asters or Brassicas,
but can sometimes help in ID, like red trillium. Bilateral symmetry means the flower can
be folded in half equally, radial symmetry means one part is repeated two or more
times, and some flowers have no symmetry. Imperfect flowers may be missing pistil,
stamen, petals, or sepals. Maples will usually only have either pistil or stamen in each
flower. See the inflorescence chart below. Peduncle attachment is similar to petioles.
7. Buds
What color are the buds? Are they sharp or rounded? Are there overlapping scales or
two halves? Is the terminal bud true or false? Are there showy leaf scars? Are thorns or
spines present? Are the buds mixed or separate?
Some buds are very obvious, like the sulfur yellow bud of Mockernut. The sharpness of
buds can be used to distinguish the oaks, black oak is sharp while white oak is rounded.
Most buds have overlapping or imbricate scales, but tulip has two large halves or is
valvate. Some are even “naked” like Witchhazel. Buckeyes have false terminal bud,
which appears slightly beside the end instead of directly on the end of the twig. Walnut
has a very showy leaf scar called a monkey face. Locusts are large dark thorns and
greenbrier has many small spines. Some species have mixed buds, flowers and leaves
are present together, while most species physically separate leaf and flower buds.
8. Bark
Is the bark smooth, scaly and furrowed, or coming off in strips? What color is it? Are
there obvious lenticels? Does it appear to change with age?
Bark texture can be difficult to determine, but general categories like smooth and scaly
can help differentiate. Serviceberry and American beech have very smooth bark while
sycamore is scaly and flaking. Some hickories are well known for shagging off in strips
while some maples have similarly deep furrows and linear bark. Barks range from light
gray to dark brown. Tulips are light gray and Sycamores are white, yellow, and gray.
Sugar maple is infamous for the changes its bark goes through throughout its life.
9. Fruits
What kind of fruit is present? Does it stay on the plant after ripening?
Some common types: acorns, “nuts”, beans, samaras, wafers, berries, achenes. Some
fruits stay on longer, like redbud, which can be used for ID.