How to Identify a Tree: Leaves, Bark, Shape and Where It Grows

Most people try to identify a tree by staring at a leaf and comparing it to pictures. It works eventually, but it is slow, because thousands of trees have broadly similar leaves.

Botanists work differently. They ask a short series of either-or questions, each of which eliminates a large fraction of the possibilities. You can do the same in about ninety seconds.

Question 1: opposite or alternate?

Look at where leaves attach to the twig. Do they come off in matched pairs directly across from each other, or do they stagger along the twig one at a time?

This is the single most useful question in temperate tree identification, because the vast majority of trees are alternate. Only a small group are opposite, and in North America there is a mnemonic for it: MAD Cap Horse. Maple, Ash, Dogwood, the Caprifoliaceae family (honeysuckles and viburnums), and Horse chestnut.

So if the leaves are opposite, you are already down to a handful of candidates. If they are alternate, you have ruled out that group entirely.

Check on a healthy twig near the end of a branch, and check two or three twigs, since damage can make one look misleading.

Question 2: simple or compound?

Is each leaf a single blade, or is it made of several leaflets on a shared stalk?

The trap here is that a compound leaf looks like a small branch with leaves on it. The test: find the bud. A true leaf has a bud where its stalk joins the twig. Leaflets do not have buds at their base. So if there is no bud, you are looking at a leaflet, and the whole assembly is one leaf.

Compound narrows things a great deal: ash, hickory, walnut, pecan, black locust, sumac, box elder, mountain ash, honey locust.

Question 3: needles, scales or broad leaves?

For conifers, count the needles per bundle, because that alone identifies most pines.

• Needles in bundles of 2, 3 or 5. Pine. Eastern white pine has 5, which is handy because "white" has five letters.
• Needles single, flat, soft, two white lines underneath. Fir. Flat needles do not roll between your fingers.
• Needles single, four-sided, sharp, roll easily between finger and thumb. Spruce. Spruce also leaves little peg-like stubs on the twig when needles drop.
• Scale-like, overlapping, flattened sprays. Cedar, cypress, arborvitae, juniper.
• Needles in soft tufts that drop in autumn. Larch or bald cypress. Yes, some conifers are deciduous.

Question 4: leaf edges and lobes

Now the details are worth something, because you have already narrowed the field.

Lobed with pointed tips and bristles. Red oak group.
Lobed with rounded tips, no bristles. White oak group.
Lobed with the lobes meeting in a star, opposite arrangement. Maple.
Star-shaped but alternate. Sweetgum, which people constantly call a maple.
Toothed, asymmetric base where one side starts lower than the other. Elm. That lopsided base is diagnostic.
Heart-shaped. Basswood, catalpa, redbud.
Triangular with a flattened stalk that makes the leaf tremble. Poplar or aspen. The flat stalk is why they quake.

Question 5: bark, and the whole shape

Bark matters most in winter and for separating species with near-identical leaves.

White peeling in papery sheets is birch. Smooth grey like elephant skin, often carved by teenagers, is beech. Deep interlacing ridges in a diamond pattern is white ash. Shaggy plates peeling at both ends is shagbark hickory. Mottled patches of cream, olive and grey, looking like camouflage, is sycamore or plane. Very dark, deeply blocky like burnt cornflakes, is black cherry.

Step back for the silhouette too. Elms vase outward, pin oaks droop at the bottom and rise at the top, poplars stand narrow and columnar, and a lone open-grown oak spreads far wider than the same species crowded in a wood.

Question 6: where is it standing?

Habitat and geography do more work than people credit.

A tree in standing water is a short list: bald cypress, willow, silver maple, red maple, sycamore. A tree thriving in dry sandy soil is a different short list. And native range matters, since if you are in Florida you can rule out most of the northern hardwoods immediately.

Street trees are the exception and will happily break every rule, because cities plant whatever tolerates salt, drought and pollution regardless of where it came from.

What to photograph for a reliable ID

If you are going to check with an app, take four shots rather than one. This is the difference between a confident answer and a guess.

1. A single leaf laid flat against a plain background, such as a hand, a path or a sheet of paper. Not against other leaves.Shot 1
2. The twig showing how leaves attach, so opposite versus alternate is visible.Shot 2
3. The bark at chest height, close enough to show texture.Shot 3
4. The whole tree from far enough back to see its shape.Shot 4
5. Anything reproductive if present: flowers, acorns, cones, samaras, berries. These are the most reliable features in botany and beat leaves every time.Shot 5, if available

Where people go wrong

Using a juvenile or sucker leaf. Growth low on the trunk and on young saplings is often a different shape from mature canopy leaves, sometimes dramatically. Pick a leaf from a normal outer branch.

Photographing green against green. The most common cause of a bad result. Put a hand behind the leaf.

Trusting leaf shape alone on oaks and maples. Both hybridise freely and vary enormously within a species. Use the acorn, the bark and the arrangement.

Forgetting cultivars exist. A purple-leaved ornamental cultivar can look nothing like the wild species it was bred from.

Identium handles this from a photo and gives you the botanical name, the family, the native range, and mature size, which is the information that actually matters if you are deciding whether to plant one. Take the leaf and twig shot together and you will get a much better answer than from a leaf alone.