Generally, there are two types of leaves that are categorized according to the design of the leaf’s lamina, which is the level surface that shows the overall shape of the leaf. This is the part responsible for photosynthesis and transpiration in the plant. See below:
1) The Simple Leaf
This is where a single leaf (which is not divided into multiple leaflets), is completely connected to its stem (or petiole) which is in turn directly connected to a branch or twig. Common examples are banana, sweat gum, mango, oaks, guava, maple, black cherry, and black gum trees/plants.
2) The Compound Leaf
This leaf consists of several leaflets that each have their own stalk and are attached to the midvein, which is then connected to a branch/twig. Examples of compound leaves are from the clover, rose, poison ivy, baobab, desert cotton, and horse chestnut plants/trees.
Compound leaves are then further categorized into two types based on the kinds of leaf veins and how they are arrayed in the lamina:
2.1) Palmately compound leaves
Think about the way our fingers are joined to the palms of our hands – the leaflets spread outward from the end point of the stem/petiole.
The palmately compound leaf is then further classified based on the number of leaflets:
one leaflet – unifoliate
two leaflets – bifoliate
three leaflets – trifoliate
four leaflets – quadrifoliate, and
anything more than four leaflets – multifoliate
2.2) Pinnately compound leaves
Now visualize a feather – the leaflets of pinnately compound leaves are positioned symmetrically along the centre of the leaf where they are attached to the midrib (stem).
The pinnately compound leaf is then further classified based on how many times the leaflet is connected to the midrib:
2.2.1 unipinnate – single leaves attached to opposite sides of the midrib (the feather).
2.2.2 bipinnate – this is where several unipinnate leaves are attached to opposite sides of the midrib (multiple feathers glued to a bamboo skewer stick).
2.2.3 tripinnate – now unipinnate leaves are attached to opposite sides of a midrib and several of these are in turn connected as “unipinnate leaves” to the main midrib (multiple feather skewers glued to a broomstick).
Leaves do get more complex, but now you have the basic knowledge of the different kinds of leaves.