Fall tree identification, in the order that works

Why color is the weakest clue

The Harvard Forest account of leaf color change explains what you are looking at. All leaves lose chlorophyll through the season, faster before leaf fall. Some carotenoid pigments stay behind, which gives yellow. Red comes from anthocyanins made just before the leaves drop; Harvard Forest calls red the most common autumn color and reports that about 70 percent of its trees and shrubs produce anthocyanins. Anthocyanin mixed with chlorophyll gives brownish tones, and with carotenoids, orange.

The same page warns against trusting color. Sugar maples vary from one tree to the next, and red maples vary within a single tree and even within one leaf. A red maple can be scarlet, orange or yellow, and two sugar maples on the same street can turn a week apart. That is why this guide puts color fourth.

Timing: who turns first and who turns last

Timing is a better clue than people expect, because the order holds from year to year even when the dates shift.

• Early. UGA Extension notes that sourwood leaves often change color and fall while most other species are still green. Clemson Extension names winged and staghorn sumacs among the first to show color.
• Middle. Maples, sweetgum, black gum, sassafras and hickories. Clemson describes sweetgum giving yellow, orange, maroon and purple "regardless of the weather", black gum turning orange, sassafras mixing yellows, oranges, reds and sometimes purples, and hickories a rich golden-yellow.
• Late. UGA says oaks tend to be the last to change. Clemson adds that the larger-leaved oaks peak after the maples fade, and singles out scarlet oak as the best oak for fall color.

So a tree still green when the maples around it have dropped is often an oak, and a small tree already scarlet in early September in the Southeast may be a sourwood or a sumac.

Fruit, nuts and seeds: the fall-only clues

Many trees carry their fruit in September and October, and fruit separates trees whose leaves look alike.

Walnut and hickory. Both have alternate compound leaves that turn yellow. The husk decides. NC State describes the black walnut nut, 1 to 3 inches across, inside a yellow-green husk that does not split and stains skin and clothing, ripe in October. Shagbark hickory's husk, says NC State, is 1.5 to 2 inches across and splits into four parts when the nut is ripe, also in October. Look for walnuts and hickory husks under the tree; the seeds and nuts guide covers the rest.

Ash. White ash bears single-winged seeds up to 2 inches long in drooping clusters, ripening in fall and often staying through winter, according to NC State, on opposite, feather-like leaves of usually 7 leaflets. Paired wings instead would point to a maple.

Acorns. Any acorn means an oak, and with the leaf it often tells you the group: bristle-tipped lobes for the red oaks, rounded lobes for the white oaks.

Autumn tree identification in the UK

In Britain and Ireland, the fruit is again the best partner to the leaf.

Spindle is the most striking autumn small tree in hedges. The Woodland Trust describes shiny, finely toothed leaves that turn a rich orange-red before falling, bright pink fruits with orange seeds, and green twigs with light brown corky marks. It warns that leaves and fruit are toxic to humans. In leaf it is easily confused with dogwood, but the pink fruit settles it.

Sycamore, field maple and Norway maple all have palmate, lobed leaves and winged seeds. The Woodland Trust gives sycamore's leaves as five-lobed and 7 to 16 cm, often on red stalks on younger trees, and says its V-shaped pairs of seeds meet at a narrower angle than those of the other two maples. Fallen bunches of seeds under the tree make this an autumn test.

Fallen leaves and what is left on the tree

Leaves on the ground are easy to collect, but they travel. Pick several from directly under the crown and compare them with leaves still on the branches. Note whether a "leaf" is really one leaflet of a compound leaf: ash, walnut, hickory and locust leaves often break apart as they fall, scattering single leaflets that look like whole simple leaves.

Late in the season, trees that still hold dry brown leaves after the others are bare are worth a look too; the winter tree identification guide picks up from there with buds and twigs.

Using a photo in fall

A photo of one typical leaf, plus a nut, acorn or seed cluster if there is one, gives the best lead; a wide shot of a colorful crown gives the least. Tree Identifier names a tree from one photo, and sugar, red and Norway maple, sweetgum, black gum, ginkgo, sassafras, tulip tree and several oaks are among the species in its Collection. It shows no confidence score and no list of alternatives, so check the answer against the leaf and fruit clues above. The Tree Map in Tree Identifier keeps the spot, so you can return in spring to see the flowers and confirm the name.