Identifying Plants to Observe - Part 1

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

The woody trunk of a horse chestnut tree.

Does the plant have bark? Are all the stems green ? Is it annual or perennial?

A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem.

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

Opposite leaves grow in pairs on opposite sides of a stem as seen in the milkweed (top). Alternate leaves switch sides down the stem as seen in the grapevine (bottom).

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.

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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?

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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.