Which tree has catkins? Check the month, the leaf and what comes after

Late winter, before the leaves: hazel and alder

The first catkins of the year belong to hazel and alder, and they open on bare branches.

Hazel is a shrub or small tree, about 8 m tall when left uncut. The Woodland Trust describes yellow male catkins, the "lambs' tails", hanging in clusters from mid-February before the leaves, with tiny bud-like female flowers marked by red styles on the same tree. Small green catkins already show in autumn, ready for the next year. The nuts ripen in late summer, and the leaves are round to oval, doubly toothed, hairy and pointed at the tip. The hazel page covers the planted hazels and the American hazelnut.

Alder is the answer to "tree with catkins and small cones". The Woodland Trust describes hanging male catkins 2 to 6 cm long that turn yellow and open between February and April, and female catkins that start as small red ovals, turn green and then brown and woody after pollination. Those tiny cone-like fruits stay on the tree all year, so an alder shows last year's cones beside this year's catkins. The leaves are 3 to 9 cm long, racquet-shaped, with a rounded or notched tip, never pointed. Alder grows by rivers, ponds and wet woods; see the alder page for the North American species.

Silky catkins and separate sexes: willows and poplars

Willows and poplars carry male and female catkins on separate trees, which is why one tree in a row may shed cotton in summer and its neighbor never does.

Pussy willow is the willow most people notice. NC State describes silky gray male flowers in spring before the leaves emerge, on separate male and female plants, and alternate leaves 3 to 4 inches long with a gray-green underside, on a shrub or small tree 10 to 20 feet tall. The willow page sorts the tree willows by leaf and bark.

Eastern cottonwood is the poplar of North American river bottoms. NC State describes catkins 2 to 4.5 inches long emerging in March and April before the leaves, with red stamens on male trees and green ovaries with yellow stigmas on female trees. In summer the female catkins split and release seeds with silky white hairs. The leaves are triangular, 3 to 6 inches long, with coarse, curved teeth, and the tree reaches 75 to 100 feet. That cotton is covered on the white fluff page.

Spring, with the leaves: birch, oak and walnut

Silver birch opens its catkins from April to May. The Woodland Trust describes long, yellow-brown male catkins hanging in groups of two to four at the shoot tips, and short, bright green female catkins standing upright. After pollination the female catkins thicken and turn dark crimson, then break up in autumn into masses of tiny seeds. White bark and small, triangular, toothed leaves confirm it; the birch page covers the North American birches.

Oaks are the source of the heaps of stringy catkins on driveways in spring. NC State describes northern red oak's male flowers as drooping yellowish-green catkins about 2 to 4 inches long, blooming from April to May, while the female flowers are tiny, about 1/8 inch, and become acorns. The leaves have 7 to 11 shallow lobes with bristle-tipped teeth. Other oaks carry similar catkins; the oak page separates the red and white oak groups.

Black walnut answers "tree with catkins and nuts" in the eastern US. NC State describes single yellow-green male catkins 2.5 to 5.5 inches long on last year's wood from April to May, compound leaves 12 to 24 inches long with 15 to 23 leaflets, and a nut 1 to 3 inches across inside a yellow-green husk that heavily stains skin and clothing, ripening in October. Its range runs from northeastern Canada west to North Dakota and south to Texas and Florida.

Catkins all winter: hophornbeam

A small understory tree with short catkins visible all winter is likely an American hophornbeam. NC State describes preformed male catkins 1/2 to 1 inch long in clusters of three that hang on through winter and open in April, birch-like doubly toothed leaves, and fruit in drooping clusters of papery sacs that look like hops and persist from summer through winter. Mature bark breaks into loose, scaly, grayish-brown plates. It grows 20 to 35 feet tall in dry, rocky woods from Nova Scotia and Manitoba south to Florida and Texas. Its cousin the hornbeam has smooth, fluted bark; the beech and hornbeam page explains the difference. The ironwood page separates it from musclewood.

Using a photo

Catkins alone are a weak clue in a photo, because related species carry near-identical ones. Include a leaf, a stretch of bark or last year's fruit, such as alder cones or hazel husks. Tree Identifier names a plant from one photo, and alder, silver birch, hazel, eastern cottonwood, black walnut and northern red oak are among the species in its Collection. It shows no confidence score or list of alternatives, so check the result against the month and fruit columns above. The follow-up chat under each result can answer questions such as why a willow has no catkins, and the Tree Map remembers where you found a tree so you can go back for its leaves after the catkins fall.