Trees are a valuable part of all of our lives. Trees create the oxygen we breathe, grow the food we eat, provide us with shade on hot days, and beautify our homes and neighborhoods. Learning tree identification is the first step in appreciating this incredible group of woody plants that impact our lives so profoundly. Once you learn to call a tree by name, you will begin to notice more and more features and facts about that type of tree.
The technical definition of a tree is a woody plant that has a single trunk that grows to a considerable height.
Let’s rule out some broad categories of plants that aren’t trees.
Any plants that die back to the ground in winter are never trees. This group includes herbaceous and perennial wildflowers. Vines also aren’t trees (although some tree branches have vine-like habits).
The line between bush and tree can be blurry. Bushes, like trees, are also woody plants. However, if the plant has many trunks coming from the ground and is less than 15 feet tall, it is a bush rather than a tree. Rarely, some ‘bushes’ can reach up to 40 feet high. Nature never fits perfectly in the boxes we prescribe to it.
Botanically speaking, only dichotomous plants can produce wood. This means that monocots are never trees. Palm ‘trees’ and bamboo fall under the monocot category and therefore aren’t trees (you can still think of them as trees though, only snobby botanists will call you out on this).
There are about 60,000 species of trees on Earth. This accounts for about 20% of all plant species on the planet. If you’re in mainland Alaska then your task as a tree identifier is pretty easy. There are about a half dozen species of trees in that massive area! If you’re in Florida you’d better get to work because there are hundreds of species in that state. Generally, U.S. tree diversity is much higher east of the Mississippi river compared to the West.
A major distinction between trees groups is coniferous trees and broadleaf trees. Don’t get these terms mixed up with evergreen and deciduous. These terms mean different things!
A conifer tree has needles instead of leaves. These needles are thin and long. Christmas trees, for example, are always a type of conifer. Famous examples of conifers are redwoods, giant sequoias, and monkey puzzle trees. Cedars, junipers, and cypresses are conifers that have scales instead of needles. There are only about 600 species of conifers in the world, meaning they represent only about 1% of all tree species.
Broadleafed trees make up the vast majority of tree species. These trees have true leaves, like a sycamore or a red oak.
An evergreen tree is a tree that never drops its leaves or needles. Think spruce, fir, or juniper. Deciduous trees drop all of their leaves for winter. Think dogwood, hickory, or horse chestnut.
People often think of the terms conifer and evergreen as meaning the same thing. This is incorrect. Likewise, broad-leafed is not interchangeable with deciduous.
Almost all conifers are indeed evergreen. However, tons of broad-leafed trees are also evergreen. Magnolias in the American south and live oaks in the American southwest and eucalyptus are common examples of evergreen broad-leafed trees. In fact, there are tons of broad-leafed evergreen tree species since most species of trees live in the tropics where trees don’t need to drop leaves because of a cold winter.
Larches, dawn redwoods, and baldcypresses are all kinds of conifers that drop their needles in the fall. These types of trees are deciduous conifers.
There are three main methods for learning tree species; direct, in-person teaching, tree identification guides, and plant identification apps.
The first, and in my opinion most valuable, is to go out with someone who knows the trees and can teach you firsthand. Schools and other institutions offer classes and workshops on plant identification. Perhaps your friend can teach you a thing or two as well. Going to an arboretum or a botanic garden is also a great way to learn trees since trees in these places are usually identified with their species name.
Field guides are only helpful if you know how to use them. If you’re looking for a field guide, try to get the one that is the most specific to your region. A guide to the ‘Trees of Western North Carolina’ will be much more useful for someone living in Asheville than a generic ‘Trees of the South’ guide. Similarly, that ‘Trees of the South’ guide will be better than a ‘Trees of North America’ guide.
Some field guides are full of pictures or drawings. These sorts of guides act as visual references for tree ID. However, since there are sometimes hundreds of tree species, these guides usually only list the common tree species. For most people, this is sufficient.
More technical, dichotomous keys are the most accurate guides for identifying trees. The niche botanical vocabulary and lack of pictures in these guides are usually daunting for the layperson. People usually need to take botany classes to learn how to use these dichotomous keys.
Lastly, plant identification apps can be quite effective for quick identification. Apps are frighteningly accurate in many situations. All you do is take a picture of the plant and the app will suggest likely plant species based on the appearance and location of the plant. The future is here!
Paying attention to features both large and small helps aid proper tree identification. Details as small as the veins on the leaves or as large as the general branching structure of the tree can give you valuable clues into what species of tree you are looking at.
There are too many types of tree leaves to cover in this guide, but let’s touch on some basics. Leaves can be either simple or compound. A simple leaf has no divisions whereas a compound leaf is made up of several leaflets. Leaves can be palmately compound, like the fingers coming off of your palm. Maple leaves are palmately compound. Leaves can also be pinnately compound, which means they look like a fern. Acacias sometimes have pinnately compound leaves.
The leaf margins are also important to notice. A leaf margin is the shape of the edge of a leaf. A margin is entire if it has no texture to it. Leaves can have serrate or toothed margins, like a bread-cutting knife, along with a whole host of other margin types. Oak leaves generally have lobed margins. There are a few dozen types of leaf margins to learn.
The general leaf shape can give clues to the tree species as well. Is the leaf shaped like an oval or a heart? Lanceolate, oblong, oval, and cordate are just a few of the possible leaf shapes.
Leaf size, the shape of leaf tips, color of the top side versus underside, venation, and even the shape of hairs on the leaves can also be used to identify trees.
Don’t rely on tree flowers for identification! This is for one simple reason; flowers are only present for a short time every year. However, if you do find yourself lucky enough to be identifying a tree with flowers, they are often quite helpful in distinguishing between different tree species.
Get your hands on one of the flowers (or cones) and dissect it with your fingers. Every possible part of the flower you can see has a technical botanical name. The same types of aspects you noticed on the leaf can help with flowers. For example, the shape of the flowers, the margins of the flowers, the hairs on the flowers, and the colors of the flowers are all clues towards finding the right tree species.
While the teeny tiny details of flowers and leaves can get you to the right tree, you often need to look at the overall tree structure as well. Is the tree wide or tall? Does it have tons of branches or just a few big ones? Can you see through the canopy or is it fully shaded? Is the base of the tree enlarged by the roots or not?
Botanists often refer to the overall gestalt of a plant. Gestalt is a German word that translates loosely to ‘entire pattern’. For plant ID nerds, this means the patterns that the entire plant seem to exude. Since plants from the same species can look very different based on environmental factors, a hunch based on the plant’s gestalt is often the quickest and most accurate way to identify the plant! The more ID repetitions you get, the more accurate your gestalt for a plant species becomes. Once you have seen 1,000 of the same tree species in tons of different places, you will no doubt be able to pick out that same species in any forest.
Once you feel like you have a good guess on the group of trees your tree is in, you can use environmental factors to parse it out from similar species. Often times you can whittle down potential tree species by taking the geographic range and habitat of a species into account. For example, incense cedars look similar to western red cedars, but western red cedars don’t grow in the Sierra Nevada mountains of California. Therefore, if you see a cedar in the hills of those mountains, you don’t need to pick apart the differences between the two cedars because only the incense cedar lives in that ecosystem.
You can weed out additional similar tree species by taking the elevation, sunlight, soil moisture, geology, and slope direction into account.
Learning your local trees, whether they are gnarled oaks or grand chestnuts, adds meaning to the landscape and combats plant blindness. Once you learn tree species, you can pay attention to which bird species prefer which kinds of trees. You can notice which species of trees tend to grow next to each other. If you’re willing to put in the time, the natural world has infinite fascinating stories to tell.