About this tutorial
Imagine you are walking down a country lane. It is early summer, the trees are bright and fizzing with new leaves. You stop to admire one, running your fingers across the smooth, green surface. It is such a beautiful leaf… But, what is it? In this tutorial, we will have a look at how to describe tree leaves in order to help you in identifying trees by their leaves.
An overview of tree leaves
There are several ways to identify trees, such as by leaf, bark, bud, flower and growth habit and location. Among these, for beginners, one of the easiest ways to identify trees is by looking at their leaves.
When trying to identify trees by their leaves, there are several things we can look at:
- Leaf shape
- Leaf margins
- Tips and bases
- Growth habit
How many leaf types are there?
Leaves can be classified in several ways. First, by tree type – deciduous or evergreen, and second by growth type – simple or compound.
- Deciduous trees provide our beautiful autumn colours. They are the trees which shed their leaves in autumn.
- Evergreen trees are those, such as christmas trees, which remain green all year round.
- Simple leaves have one single leaf per twig.
- Compound leaves have multiple leaves per twig.
You may also come across the terms ‘broad-leaf’ and ‘needle-leaf’. Generally speaking, broad-leaf trees are deciduous and needle-leaf trees are evergreen. However, not all deciduous trees are broad-leaf. And not all needle-leaves are evergreen.
For example, strictly speaking, larch is a needle-leaved conifer. But, unlike other conifers, it sheds its leaves in autumn. Holly is strictly a broad-leaf, but has a tendency to remain green all year round.
Identifying leaves by their shape
One of the first clues to focus on when attempting to identify tree leaves, is the shape of the leaf.
There are many different leaf shapes, however, our most common leaf shapes, are:
- Acicular (needle-shaped)
- Cordate (heart-shaped)
- Deltoid (triangular)
- Digitate (finger-like)
- Elliptic (oval)
- Lanceolate (pointy and both ends)
- Linear (long and thin)
- Lobed (as the name says)
- Obcordate (upside-down heart-shaped)
- Orbicular (circular)
- Palmate (like a hand)
- Rhomboid (diamond-shaped)
Can you guess which shapes these common leaves are?
Describing leaf margins
After considering their shape, the next clue to look at when trying to identify tree leaves, are the edges of their leaves, or leaf margins.
Broadly speaking, leaf margins can be classified as:
- Entire (smooth)
- Crenate (small, little waves)
- Dentate (with teeth)
- Lobed (as the name says)
- Parted (deep indentations)
- Serrate (like a saw)
- Sinuate (wavy)
Can you describe these leaf margins?
Leaf tips and bases
Can you guess what leaf tips and bases are? They are the tops and bottoms of a leaf. The tip or apex, is the bit furthest from the twig and the base is the bit where the leaf joins the twig (by the stalk).
We often assume leaves are all pointy at the tip and rounded at the base, but if you look closely you will notice they are not all like that. In fact, they can be all sorts of shapes.
- Tips can be sharp and pointed, blunt, indented or rounded, heart-shaped or square.
- Bases can be symmetrical or asymmetrical, wide or narrow, pointy, heart-shaped, square or round.
Can you describe these leaf tips and bases?
What are leaf veins?
A leaf’s veins act much like our veins. But, instead of oxygenated blood, a leaf’s veins transport sugary and mineral-rich liquid around the leaf.
Like leaf shapes, margins, tips and bases, you can also use the leaf’s veins to help guide you in putting names to faces.
Some veins are neatly organised and branch off a larger, central vein. Others fan out towards the tip from the base of the leaf. Some leaves have long, parallel veins, and in others they are higgledy-piggedy all over the place.
How are leaves arranged?
The way leaves are arranged on their twigs can also be a big clue in trying to identify trees. There are three ways a tree’s leaves can be attached:
- Alternate – Alternate leaves are arranged step-wise on either side of the twig, first one, then the next, then the next and so on…
- Paired – Paired leaves are arranged in twos up the twig – two, by two, by two and so on…
- Whorled – Whorled leaves are arranged in little groups or clusters up their stems.
Can you describe these leaf arrangements?
At the beginning of this post, I spoke about simple and compound leaves. As a recap, simple leaves are single leaves and compound leaves are groups of leaves.
Compound leaves can be arranged up their main stems, or fanning out from a central base and are described as:
- Pinnate – Pinnate leaves are arranged on either side of their main stems.
- Doubly pinnate – Doubly pinnate leaves are like pinnate, but every leaf blade is further divided into little pinnate leaves. Think of ferns and bracken.
- Palmate – Lastly, palmate leaves fan out of a central base.
Can you guess which type of compound leaf these are?
Last but not least, we will have a quick look at some coniferous leaves. Because, while we might assume all conifers or evergreens have needle-like leaves, at closer glance you will notice they are all different too.
Conifers can be identified by their leaves’ texture and arrangement just like broad-leaf trees.
- Scaly, fern-like needles are often cypress or cedar
- Clustered, rosette-like needles are larch
- Feathery leaves are hemlocks
- Long needles arranged in little bundles or 2, 3 or 5 are pines
- Short, square needles attached to their twig by little pegs are spruce
- Short, flat needles are firs
These leaves come from Scot’s pine, Douglas fir and cedar.
Well… there we go! A (sorry, not-so-quick) summary of how to identify trees by their leaves. Hopefully, you should now be able to confidently look at and describe a leaf in order to correctly identify that leaf in your field guides and so, name that tree! I hope you enjoyed it? Happy nature walking and see you soon!
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