Botany: Leaf and Vegetative Terminology

Question 1

Why is it important to learn about leaves?

Answer 1

the ability to notice and describe leaf patterns is central to plant identification.

Question 2

What are the three types of leaf arrangement?

Answer 2

alternate, opposite, whorled

Question 3

alternate arrangement

Answer 3

leaves that take turns growing around the stem

Question 4

opposite arrangement

Answer 4

two leaves that grow directly across the stem from each other

Question 5

whorled arrangement

Answer 5

three or more leave grow out from the same point on the stem

Question 6

What is the most common arrangement of leaves?

Answer 6

alternate

Question 7

What’s the difference between a simple and divided/compound leaves?

Answer 7

Simple leaves aren’t further divided into smaller units (like a maple leaf). Divided leaves are segmented into subleaves called leaflets.

Question 8

pinnately compound leaves

Answer 8

like a feather; leaflets arranged on either side of the central elongated axis

examples: ash (Fraxinus spp.), hickory (Carya spp.), and sumac (Rhus spp.).

Question 9

bipinnately compound leaves

Answer 9

doubly pinnate or twice compound; leaflets are further divided into even smaller leaf segments.

examples: mimosa (Albizia julibrissin) and honey locust (Gleditsia triacanthos).

Question 10

tripinnately compound leaves

Answer 10

triply pinnate or thrice compound; leaflets are further divided into smaller leaf segments, which are in turn divided into even smaller segments. This type of leaf is more common in the tropics and somewhat rare in the temperate world.

example: heavenly bamboo (Nandina domestica).c

Question 11

palmately compound leaves

Answer 11

leaflets radiate from a central point, much like fingers on the palm of a hand.

Examples: buckeye (Aesculus spp.) and horse chestnut (Aesculus spp.).

Question 12

petiole

Answer 12

the leaf stalk (like the leash of a leaf)

Question 13

midrib

Answer 13

main central vein running up the center of a leaf.

Question 14

blade

Answer 14

the surface of the leaf, the broad photosynthetic surface of the leaf.

Question 15

margin

Answer 15

the edge or border of a leaf

Question 16

node

Answer 16

part of the stem from which one or more leaves emerge (the area where the leaves and stem are joined)

Question 17

stipule

Answer 17

leafy appendage (extra doodad) at the node; green outgrowths at the base of the petiole.

Most leaves don’t have stipules; so when you see one, take note. The rose and bean families are world-renowned for their stipules.

Stipules are extremely variable in appearance and attachment to the plant. Some of the best plants to examine stipules are roses (Rosa spp.) and red clover (Trifolium pratense).

Question 18

lateral bud

Answer 18

a bud that rests in the node, between the petiole and stem (as opposed to the tip of a branch).

Also called axillary bud. Lateral buds are useful in figuring out whether a leaf is simple or compound.

Question 19

basal leaves

Answer 19

leaves that emerge from a central point in the earth rather than from a stem.

Leaves are clustered at the base of the plant and form a rosette, which is often called a basal rosette.

Sometimes plants have basal and stem leaves (flowering burdock [Arctium spp.] or yellow dock [Rumex crispus] are examples), and sometimes they have only basal leaves (dandelion [Taraxacum officinale], for example).

Question 20

lobed

Answer 20

a leaf with deeply indented margins.

Examples are dandelion (Taraxacum officinale), most oaks (Quercus spp.) and maples (Acer spp.). Note that leaves can be lobed and toothed.

Question 21

pubescent

Answer 21

hairy.

This is a general botanical term for hairiness on any organ.

Question 22

glabrous

Answer 22

smooth, no hairs.

Question 23

margin types: entire

Answer 23

no teeth; an even border on the outside

Question 24

margin types: serrate

Answer 24

saw-toothed edge with upward pointing teeth

Question 25

margin types: dentate

Answer 25

saw-toothed edge with the teeth pointing out at right angles

Question 26

margin types: crenate

Answer 26

rounded teeth or scalloped edge (lemon balm)

Question 27

What’s the difference between a leaf and a leaflet?

Answer 27

A subleaf is a part of a leaf. In divided leaves, a leaf is split into smaller unites, or “subleaves”, which are called leaflets

Question 28

In divided leaves, what’s the difference between pinnately compound leaves and palmately compound leaves?

Answer 28

Pinnately compound leaves are like a feather; leaflets are arranged on either side of the central elongated axis.

In palmately compound
leaves, the leaflets radiate from a central point, much like fingers on the palm of a hand.

Question 29

What makes divided leaves so tricky when we’re trying to determine leaf arrangement?

Answer 29

Divided leaves have leaflets, which may have a different arrangement than the leaves. For example, the leaflets
may be opposite, while the leaves are alternate. When we talk about leaf arrangement, we look at how the leaves
are arranged on the stem, and NOT how the leaflets are arranged.

Question 30

Lateral buds can be useful in determining whether a leaf is simple or compound/divided. Where are lateral buds located?

Answer 30

A lateral bud rests in the node, between the petiole and stem (as opposed to the tip of a branch).