Have you seen the abundance of green, these past couple of days? If so, you must have noticed the many types of leaves in every bit of nature. Let’s find out a bit more about them and how to use leaf type to determine the plant species.
First off, you can classify leaves into two types, depending on whether they have a stalk or not. That is the most basic categorisation, but usually won’t get you anywhere in determining the plant species. For now, we will only consider stalked (petiolated) leaves, as plants having leaves without a stalk are often quite difficult to determine.
We then start by identifying whether the leaves are simple and undivided, or made up of several leaflets. If they are indeed “compounded”, the leaves consist of multiple parts, all connected to a central point or central midrib. The way in which the compound leaves are built up can be quite diverse. There are hand-formed leaves, like the horse chestnut, longer rows of leaves, like with the cuckooflower (Cardamine pratensis), and many other forms.
To correctly use this trait for determination, first look if the leaflets are all connected to one point, or along an axis. Then count the number of “leaves” within the whole leave.
That all being done, you can usually narrow down the search quite a bit already. And we haven’t even really looked at the leaves themselves!
Zooming in on the actual leaves, first we check out the edges of the leave. Are they smooth? Lobed? Serrate? Many groups of plants have a typical kind of leaf edge, like the rose family has sharp, serrate leaves.
Now it’s time for the actual shape to matter. You can have many shapes and variations to shape, but in general, it will be enough to say whether the leave is round, ovate, elliptic, cordate, acicular or hand-shaped. And yes, it might very often be something in between, especially with ovate and cordate, but try to find the best fit.
(before going to the next step, you can also look at the vein arrangement as well, but as that is only necessary for difficult plants, we will skip it for now.)
Finally, it can be useful to consider the way the leaves are arranged along the stem of the plant. Are they growing exactly pairwise, or alternating? Or maybe even with three or four leaves at the same place every time?
If you have decided on all that, then you might have a very good idea of what kind of plant you are dealing with. Of course, for precise determination, you might need other information about the plant, like flowers, roots or twigs as well. But for a general idea of the plant family, this might very well work. Especially with trees and woody plants.
Whether you want to find out the species of a plant, or just enjoy nature, a bit of knowledge might make it even more interesting. So I hope this small guide to leave types has contributed a bit to your appreciation of nature. Next time you go out into nature, choose one plant to take a closer look at and really study its leaves. You will be amazed at how much you might see.
Anyway, I hope you all have a great (sunny) weekend! Enjoy!