First some simple terminology. The blade is the main part of the leaf. The petiole is what attaches the leaf to the plant. But I’m going to call the petiole the leaf stalk. It’s easier that way.
A simple leaf is a leaf in which the blade is undivided. That’s easy. A simple leaf can attach to the plant stalk a few different ways. The first way is the way you drew a flower in grade school. Flower, stem, leaf. The leaf had a leaf stalk and the leaf stalk attached the leaf to the stem.
Sometimes the leaf attaches to the plant stem without even bothering with the leaf stalk. Biologists call this “sessile”. It can be used for both leaves and flowers. But we’re going to call it stalkless.
Next, the blades can be divided. This is called a compound leaf. And each little leaf is called a leaflet.
Here is where we’re going to use a biology term because it makes sense. The term is pinnate. And it just means having leaflets arranged on either side of the stem. Try it out on your friends… ok on second thought don’t do that.
An odd pinnately divided compound leaf has leaflets on either side of the stem and a single leaflet at the tip. That would make the total number of leaflets odd. (See there really is reason to some of this madness)
An even pinnately divided compound leaf has leaflets on either side of the stem and two pairs of leaflets. That makes the total number of leaflets even.
Like anything it can get more complicated. But these three classifications of simple leaves will help us identify wildflowers. Adds