When we speak of flowers, in these cases, we’re not referring to colorful blooms with petals, as in insect-pollinated blossoms. These flowers are tiny and inconspicuous, but the blooming catkins themselves are elegant, though largely short-lived.
Species with Catkins
Trees with catkins include those of the Beech family (oaks, chestnuts), the Willow family (willows, aspens, poplars, cottonwoods), the Birch family (birches, alders, hornbeams), the Mulberry family, and the Walnut family (walnuts, hickories). In the Willow family, both male and female flowers occur in the form of catkins, and for most species, a given tree has only one type, either male or female. In the Willow genus (Salix species), many catkins are small and upright, while cottonwoods and aspens have drooping catkins.
The remaining families have mostly male catkins, although birches have small, upright female catkins. Most female flowers of these various species take other forms, usually smaller and rounder, developing later in the year into acorns, alder cones, hickory nuts, walnuts, and other fruits.
Growth and Development
Catkins form on the trees in summer, remaining tight, smooth, and closed throughout the winter. They begin to expand in early spring, with most flowering before the leaves appear, or at least before the leaves get too large. As catkins rely on wind to spread their pollen, this arrangement prevents the leaves from interfering with fertilization. After the female flowers are fertilized, the male catkins wither and drop.
The species flowering earliest are mostly willows, aspens, cottonwoods, and birches. When willow catkins flower, some species start out with a silvery fuzz (think of pussy willows), followed by stamens with yellow, pollen-bearing heads.
Cottonwoods usually grow along rivers and creeks. The female parts develop into strands of seeds attached to fluffy hairs, which facilitate the distribution of the seeds by means of wind and water. When the cottonwood seeds burst from their pods in late spring, the air fills with snowy fluff on windy days, and clumps of seeds, kept afloat by the hairs, travel downstream to possibly lodge on a bank and germinate.
Walnuts, hickories, and oaks flower a bit later, with drooping clusters of male catkins. The walnut has female flowers in small clusters at the tips of the twigs, while the oak’s female flowers occur at the leaf bases.
Each species has its own habits and forms, which are interesting to contemplate. The brief beauty of the catkin-bearing trees is one of the treats of early spring, a welcome sight as we wait for the greenery to burst.
Violet Snow - Violet Snow is a naturalist, herbalist, photographer, journalist, and outdoor educator. She has taught classes for the Appalachian ...
