Leaves of three, leave them be. A good rhyme to remember if you want to avoid coming into contact with poison ivy and other toxic plants that can cause skin irritations.
There is a wide variety of leaf shapes and sizes in nature and they help us to identify a plant and each has its own name. Different terms are used for the patterns and shapes used in leaf identification.
Some tree species make identification difficult by displaying more than one type of leaf structure, while others have such a distinct leaf pattern they can’t be misidentified. There are several leaf layers and shapes to be looked at before the leaf can be identified.
Epidermis
Leaves have an outer layer of ‘skin’ called the epidermis, just like our outer skin layer. The epidermis of a leaf is the exterior layer that always has a waxy cover called the cuticle and it will vary in thickness. The epidermis may or may not support leaf hairs, which can also be an important clue in identifying the leaf.
Leaf Shape
The shape of a leaf can vary considerably even when they are growing on the same tree or plant.
Leaf shape varies according to their position on the tree or plant, the age of the leaf, and insect or disease damage. Find a healthy leaf in its natural environment to start the identification process.
Leaf Margin
The outer edges of leaves are called ‘margins’ and these margins will either be smooth, serrated or a combination of both.
Leaf margins have at least a dozen unique characteristics. and are divided into four major classifications. All tree and plant leaves will fit into one of these four main categories:
Smooth Leaves are leaves
They are with no serration around the margins. These leaves are smooth all around. The flowering Dogwood tree and aster flowers are two examples of plants that have smooth leaves.
Serrated or Toothed Leaves
Serrated or Toothed Leaves have margins with a series of tooth-like pointed teeth around the entire leaf edge. The margins resemble the toothed edge of a steak knife and are typically found on deciduous trees. Leaves with serrated margins have better transpiration and photosynthesis early in the growing season. This enables the tree or plant to grow at a faster rate and moves sap throughout the tree sending energy to the leaves so they can make the most of their short growing season. Apple trees, black cherry trees, elms, and dahlias have serrated leaves and grow rapidly.
Lobed Leaves
Lobed Leaves have margins with an indention that go less than halfway to the leaf. The leaves will have divisions extending less than halfway to the middle of the base. This leaf shape will have distinctly rounded or pointed projections and will have their own veins that are connected to the midrib of the leaf. The midrib is the central, thick, linear structure that runs along the length of the leaf.
The white oak, red oak, sweetgum tree, and coleus have lobed leaves. Most trees and plants with this type of divided leaf shape produce very vivid fall foliage colors.
Parted Leaves
Parted Leaves have margins with an indention that extends more than halfway to the leaf midrib. The leaf margins are cut sharply and irregularly and look like they have been torn or ripped.
Sub-Categories
Within the four main categories lie many sub-categories of leaf margins shapes. Decide on the main category of the leaf using one of the four distinct shapes, then continue the identification process by looking for some of these other distinguishing leaf characteristics.
Venation Pattern
Leaves have veins that create patterns and shapes that will identify leaves. These veins carry liquids and nutrients to leaf cells. Veins also carry the products of photosynthesis back to the rest of the tree or plant.
Plant leaves have several types of veins. The central one is called the midrib. Other veins connect to the midrib and have their own unique venation patterns. These leaf veins patterns are divided into two main categories for easy identification.
Pinnate Venation leaves
Pinnate Venation leaves have veins that extend from the midrib to the leaf margin. The leaves of oak and cherry trees are good examples of this vein pattern.
Palmate Venation leaves
Palmate Venation leaves have veins that radiate in a fan shape from the leaf stalk (petiole). Maple and sweetgum leaves are good examples.
There are several sub-categories of these venation patterns that can help identify leaf shape and the tree or plant to which the leaf belongs.
Arcuate
It has rounded secondary veins that reach from the midrib to the leaf apex.
Cross-venulate pattern
It has small veins connecting the secondary veins.
Dichotomous pattern
It has veins that branch out in symmetrical pairs.
Longitudinal
It has veins that run along the leaf towards the axis.
Palmate pattern
It creates several long veins diverging from one central vein point.
Parallel venation pattern
It is several long veins along the leaf that do not intersect.
Pinnate
They are pairs of veins opposite of each other.
Reticulate
They are small veins that form an intricate pattern on the leaf.
Rotate venation pattern
It creates radiating veins that resemble the shape of flower petals.
Detective Skills
Identifying leaf shapes take botany detective skills. Look for the clues the leaves provide along their margins and veins to help you identify the plant.
Start the detective work with a healthy leaf and you’ll end up with the name of the healthy plant it came from.
Growing Vegetables in Shade
