Free tool
Tree identification key
A dichotomous key for common US trees. Pick one of two answers at each step, from needles or leaves down to a genus or species.
In short
A tree identification key is a series of paired choices that narrows a tree down one step at a time: needles or broad leaves, then opposite or alternate leaves, simple or compound, lobed or not, the edge of the leaf, and finally bark and fruit. This key covers 26 common US trees and tree groups, and every answer opens the page on that tree.
- Use a leaf that is still on the tree, and check three or four twigs before you answer about leaf arrangement.
- Can't reach the twigs? "Not sure" at the opposite-or-alternate question switches to a route that works from a fallen leaf and the fruit.
- Your answers stay in the page address, so the link to a result opens the same answer on another phone.
Tree identification key
Answer one question at a time about the leaves, then the bark and fruit. Every answer ends at a tree with a page on this site, and “Not sure” always gives you another way forward.
Question 1
Needles or broad leaves?
Look at a leaf still on the tree, not one from the ground.
Source: Aren't They All Just Pines? How to ID Needle-Bearing Trees (Cornell Small Farms Program (Peter Smallidge, Cornell University)); U.P. Tree Identification Key (Michigan Tech, maintained by Bill Cook, MSU Extension)
Nothing is sent anywhere. Your answers live in the page address, so the link opens the same step.
The whole key as a list
Tree identification key: The whole key as a list
The same key in the classic printed form: start at 1, pick the line that fits, and follow the number. Questions after the main key are the leaf-only route that “Not sure” opens.
1. Needles or broad leaves?
1a Needles, or small scale-like leaves → go to 2
1b Broad, flat leaves → go to 3
2. Needles in bundles, or one by one?
2a Needles in bundles of 2, 3 or 5, often wrapped at the base by a thin sheath → Pine (Pinus)
2b Needles attached one by one, clustered on short spur shoots, or flattened into scales → Spruce, fir, hemlock, larch or cedar (Picea, Abies, Tsuga, Larix, Thuja)
3. Palm fronds or ordinary leaves?
3a Very large fan-shaped or feather-shaped leaves (fronds), each joined to the trunk by a broad, flared base → Palm (Arecaceae)
3b Leaves on twigs and branches → go to 4
Not sure: go to 4
4. Opposite or alternate?
4a Opposite: leaves grow in pairs, straight across from each other → go to 5
4b Alternate: one leaf at each point, staggered along the twig → go to 6
Not sure: go to 26
5. Simple or compound?
5a Compound: several leaflets on one leaf stalk → go to 7
5b Simple: one blade on each leaf stalk → go to 8
6. Simple or compound?
6a Compound: several leaflets on one leaf stalk → go to 9
6b Simple: one blade on each leaf stalk → go to 10
7. How are the leaflets arranged?
7a Leaflets spread from one point at the end of the stalk, like the fingers of a hand → Buckeye or horse chestnut (Aesculus)
7b Leaflets in two rows along a central stalk, like a feather → go to 11
8. Lobed or not?
8a Lobed, the lobes spreading like a hand; fruit in joined pairs of wings → Maple (Acer)
8b Not lobed, with a smooth edge → Dogwood (Cornus)
9. Smooth or toothed leaflets?
9a Leaflet edges smooth or nearly so, at most one or two small bumps at the very base → go to 12
9b Leaflet edges clearly toothed along their length → go to 13
10. Lobed or not?
10a Lobed: the edge is cut into rounded or pointed lobes → go to 14
10b Not lobed: the edge may be toothed, but has no lobes → go to 15
11. How many leaflets, and what fruit?
11a 5 to 11 leaflets with shallow teeth; single-winged keys; bark with a diamond pattern of ridges → Ash (Fraxinus)
11b 3 to 5 leaflets with a few coarse teeth; green twigs; keys joined in pairs → Maple (Acer)
12. Small rounded leaflets, or long pointed ones?
12a Leaflets under 2 inches (5 cm); many trees carry thorns, or pairs of spines where the leaves join the twig → Locust (black locust or honeylocust) (Robinia, Gleditsia)
12b Lance-shaped leaflets, 10 to 40 on a leaf 1 to 4 feet long, each with one or two glandular bumps at its base; the crushed leaf smells bad → Tree-of-heaven (Ailanthus altissima)
13. How big are the leaflets?
13a Leaflets under 2 inches (5 cm), sharply toothed → Mountain-ash (Sorbus)
13b Leaflets over 2 inches → go to 16
14. Where do the lobes start?
14a Lobes along a central midrib, like a feather; the tree bears acorns → go to 17
14b Lobes spread from the base of the leaf, like a hand or a star → go to 18
15. Long and narrow, or broader?
15a Long and narrow: many times longer than wide → Willow (Salix)
15b Broader: oval, round, triangular or heart-shaped → go to 19
16. Count the leaflets and split a twig
16a 11 to 23 leaflets, the end leaflet often missing; the pith of the twig is chambered, divided by thin crosswalls → Walnut (Juglans)
16b Fewer leaflets, mostly 7 or fewer, the end leaflet the largest; the fruit is a hickory nut → Hickory (Carya)
17. Pointed or rounded lobes?
17a Lobes rounded → White oak group (Quercus (white oaks))
17b Lobes pointed → Red oak group (Quercus (red oaks))
Not sure: Oak (Quercus)
18. Deep star or shallow lobes?
18a Deep, star-shaped lobes; the crushed leaf smells aromatic; spiky ball-shaped fruit → Sweetgum (Liquidambar styraciflua)
18b Shallow lobes; no strong smell; fruit a ball of wind-dispersed seeds → Sycamore (Platanus occidentalis)
19. Is the leaf stalk flat?
19a Leaf stalk flattened from side to side → Poplar, cottonwood or aspen (Populus)
19b Leaf stalk round → go to 20
20. Heart-shaped?
20a Heart-shaped, with a notch at the base where the stalk joins → go to 21
20b Not heart-shaped → go to 22
21. Pods on the branches, or brick-red buds?
21a Flat pods, often attached directly to the larger branches → Redbud (Cercis canadensis)
21b Smooth, brick-red buds; leaves often in clumps → Linden (basswood) (Tilia)
22. Is the bark papery?
22a Bark papery, peeling in thin strips → Birch (Betula)
22b Bark not papery → go to 23
23. Double teeth and a lopsided base?
23a Edge doubly toothed (large teeth carrying smaller ones), and the leaf base lopsided → Elm (Ulmus)
23b Edge with single teeth, and the base even → go to 24
24. Coarse teeth and smooth gray bark?
24a Coarse, pointed teeth and straight, parallel side veins; bark smooth and gray → Beech (Fagus)
24b Finer teeth; bark not smooth and gray → go to 25
25. Glands on the leaf stalk, or shiny leaves and white blossom?
25a Two small glands on the leaf stalk; bark with horizontal rows of lenticels (short raised lines) → Cherry (Prunus)
25b Shiny, finely toothed leaves 2 to 3 inches long; masses of white flowers before or with the leaves; small round brown fruit → Callery pear (Bradford pear) (Pyrus calleryana)
26. From the leaf alone: simple or compound?
26a Compound: several leaflets on one leaf stalk → go to 27
26b Simple: one blade on each leaf stalk → go to 28
27. How are the leaflets arranged?
27a Leaflets spread from one point at the end of the stalk, like the fingers of a hand → Buckeye or horse chestnut (Aesculus)
27b Leaflets in two rows along a central stalk, like a feather → go to 29
28. Lobed or not?
28a Lobed: the edge is cut into rounded or pointed lobes → go to 30
28b Not lobed: the edge may be toothed, but has no lobes → go to 15
29. Ash keys and diamond bark?
29a 5 to 11 leaflets with shallow teeth; single-winged keys; bark with a diamond pattern of ridges → Ash (Fraxinus)
29b Other fruit, or more than 11 leaflets → go to 9
30. Where do the lobes start?
30a Lobes along a central midrib, like a feather; the tree bears acorns → go to 17
30b Lobes spread from the base of the leaf, like a hand or a star → go to 31
31. Winged keys or hanging balls?
31a Winged keys joined in pairs → Maple (Acer)
31b Ball-shaped fruit → go to 18
A tree identification key asks you to choose between two descriptions, over and over, until only one tree is left. This one is built from forestry and university keys: the U.P. Tree Identification Key maintained by Michigan Tech and MSU Extension, and Vanderbilt University's illustrated key to common trees. Each question above names the source of its facts.
How to use the key
- Pick a healthy leaf on the tree. Leaves from the sunny outer crown are the most typical. A leaf from the ground may have blown in from a neighbor.
- Answer in order. The first questions are about the leaf (needles or broad leaves, opposite or alternate, simple or compound), the later ones about the edge of the leaf, the bark and the fruit.
- Check several leaves and twigs before you answer. A single broken twig can make alternate leaves look opposite, and one odd leaf can lack its lobes.
- Use "Not sure" when you are not sure. At the opposite-or-alternate question it opens a second route that needs only a fallen leaf and the fruit. At most other questions it lists every tree that still fits, with one line to check for each.
- Read the line under the result. Every result ends with something to check on the tree, such as glands on the leaf stalk of a cherry or the chambered pith of a walnut twig. If it doesn't match, go back one step.
To share a result, copy the link: the answers are stored in the page address, so the same link opens the same answer. Nothing is sent anywhere.
How the key is built
The questions follow the order most field keys use, from features you can see at a glance to the ones that need a closer look:
- Needles or broad leaves. Pines carry needles in bundles of 2, 3 or 5, as the Cornell Small Farms Program explains; spruces and firs carry them one by one.
- Opposite or alternate. Few trees have opposite leaves. The University of New Hampshire Extension lists maples, ashes, horse chestnut and dogwoods among them, so this one question splits the key in two.
- Simple or compound. A compound leaf is several leaflets on one stalk. Ash, walnut, hickory, locust and tree-of-heaven all have compound leaves, and the key separates them by leaflet size, the leaflet edge and the fruit.
- Lobes, then the edge. Lobes along a midrib with acorns mean an oak; lobes spread like a hand mean a maple if the leaves are opposite, or a sweetgum or sycamore if they are alternate. After that, the edge of the leaf and the shape of its base sort elms from beeches and cherries.
- Bark and fruit. The last questions use the papery bark of birches, the horizontal lenticels of cherries and the white spring flowers of Callery pear.
Palms get their own question near the start: their very large fan- or feather-shaped leaves join the trunk with a broad, flared base, as UF/IFAS Gardening Solutions describes. For the full method behind these questions, see our guide on how to identify trees.
The terms the key uses
- Opposite: two leaves grow from the same point, across from each other. Alternate: one leaf at each point, staggered along the twig.
- Simple leaf: one blade on a stalk. Compound leaf: several leaflets on one stalk; the whole leaf, not each leaflet, joins the twig.
- Lobed: the edge is cut deep enough to form lobes, as on an oak or a maple. Small teeth are not lobes.
- Doubly toothed: large teeth that carry smaller teeth, as on an elm.
- Lenticels: short, raised lines or dots on the bark; on cherries they run in horizontal rows.
- Pith: the soft center of a twig. Cut a walnut twig lengthwise and the pith is divided by thin crosswalls; it is chambered.
- Keys (samaras): winged fruit. Ashes have single-winged keys; maples have keys joined in pairs.
Our guide to identifying trees by their leaves shows each of these features with examples.
When a key isn't enough
A key works best in summer, with leaves on the tree. In winter, a deciduous tree stops at the first question; use our winter tree identification guide instead, which works from buds, twigs and leaf scars.
A key also stops at the genus for many trees. Telling a red maple from a sugar maple, or a northern red oak from a pin oak, takes the species page the result opens. If you can't reach the leaves at all, a photo of the canopy, the bark or a fallen leaf in Tree Identifier gives you a name to check against the key's last question. For a tree that matters, such as one near a house, ask an ISA Certified Arborist or your county extension office.
What a photo can't settle
- A key can only name the trees it contains. A tree outside these 26, such as a magnolia or a catalpa, will end at a look-alike, so always read the "Check on the tree" line before you trust a result.
Questions people ask
What is a dichotomous key for trees?
A key that offers two opposite statements at each step, such as "leaves opposite" and "leaves alternate". You pick the one that fits the tree and follow it to the next pair, until the key names the tree. Dichotomous means divided in two.
Can I print this tree identification key?
Yes. Open "The whole key as a list" under the tool and press "Print the key". It prints the classic numbered form: start at 1, pick line a or b, and follow the number to the next question or to the tree's name. Most print dialogs can also save it as a PDF.
What if I can't reach the leaves?
Choose "Not sure" when the key asks whether the leaves are opposite or alternate. The key then asks about a fallen leaf and the fruit instead. Make sure the leaf you pick up came from the tree in front of you, not from a neighbor.
Why did the key give me a tree that doesn't match?
Usually one early answer was off, most often simple versus compound or opposite versus alternate. Read the "Check on the tree" line under the result. If it doesn't fit, press "Change" next to the answer you were least sure of and try the other side.
Which trees does this key cover?
26 trees and tree groups common in the United States, from pines and palms to oaks, maples, walnuts, birches and cherries. Each result opens a page on this site. Where there is no species page yet, such as spruce, sweetgum or redbud, it opens the guide that covers the tree.
Sources
- U.P. Tree Identification Key — Michigan Tech, maintained by Bill Cook, MSU Extension
- Illustrated key to common trees of middle Tennessee: simple-leaved trees — Bioimages, Vanderbilt University
- Illustrated key to common trees of middle Tennessee: compound-leaved trees — Bioimages, Vanderbilt University
- Aren't They All Just Pines? How to ID Needle-Bearing Trees — Cornell Small Farms Program (Peter Smallidge, Cornell University)
- Mind Your B's to Identify Winter Trees — University of New Hampshire Extension
- Palm Leaf Structure — UF/IFAS Gardening Solutions
- Tree-of-Heaven — Penn State Extension
- Callery pear fact sheet — Virginia Tech Dendrology