Catkins - The First Blooms of Spring

By Kathleen Mpulubusi

Photos by K. Mpulubusi and P. Cotterill

What are Catkins?

When the Spring Equinox arrived in Edmonton on March 21, winter still held its grip on the land. The first signs of spring are fleeting but slowly new life does start to re-appear. One of the first signs is the appearance of catkins on the branches of some deciduous trees and shrubs. From the soft, fuzzy catkins of “pussy willows" to the long, often woolly strings hanging from branches of poplars, catkins are the first “flowers” of spring. The name “catkin” comes from the Dutch word “katteken” which means “little cat.” Catkins are technically known as "aments", coming from the Latin for “strap or string."

River alder (Alnus incana ssp. tenuifolia). Image shows both the shorter female catkins and longer male pollen catkins. River Valley Whitemud, Edmonton, 2024-04-13. Photo: whitemudwayne on iNaturalist.

Catkins are cylindrical clusters of tiny flowers without petals. All of the flowers in a single catkin are either male or female. A catkin-bearing plant can be either monoecious (both male and female flowers on the same plant) or dioecious (male and female flowers on separate plants). Most catkin-bearing plants are pollinated by wind, with the tiny pollen grains easily released from the hanging catkins. Willows, though, are an exception and, equipped with nectar, are primarily insect-pollinated. Deciduous plants produce catkins before the leaves develop allowing wind-borne pollen to move unimpeded by foliage. This also makes things easier for the many early-pollinating insects that rely on the pollen and nectar produced by the catkins. Dispersal of pollen and seeds by wind allows plants to increase their distribution and maintain genetic diversity. 

Local Catkin-bearing Trees and Shrubs

Trembling Aspen (Populus tremuloides)

Trembling aspen trees are dioecious with male catkins on one tree and female catkins on another. The catkins first appear in early to mid April and gradually lengthen up to 4 cm long. 

Trembling aspen (Populus tremuloides). Left: catkins emerging from bud. Centre: male catkins. Right: female catkins.

Balsam poplar (Populus balsamifera), the common tree of our river valley floodplains, has similar but more robust catkins, which open slightly later than aspen.

Willows (Salix sp.)

Willows are also dioecious with separate male and female plants. The flower buds of willows can emerge as early as March, when their covering of insulating grey hairs creates the “pussy” effect, but in fact the flowers do not open until May in most species. Unlike poplar catkins, willow catkins remain erect on the twig until they are forming fruit. Willow catkins are an important food source for many early-emerging insects. Male catkins produce both pollen and nectar while female catkins produce nectar only. Willow catkin nectar is a highly concentrated energy source. Insects that visit willow catkins include honeybees and native solitary bees, such as mining bees and sweat bees. Other visitors include syrphid flies, beetles, and the Mourning Cloak butterfly which is one of the earliest butterflies to emerge in spring. 

Willow (Salix spp). Left: early stage. Centre: male catkins. Right: female catkins.

Birch (Betula sp.)

Birch trees are monoecious with both male and female catkins on the same twigs. 

The male catkins are yellowish brown and hang from the ends of twig tips. Female catkins appear with the new leaves and stand erect from the ends of twig tips.

Alaskan paper birch (Betula pendula ssp. mandschurica). Left: male catkins. Right: female catkins.

Beaked hazelnut (Corylus cornuta)

Beaked hazelnut is monoecious with very distinctively different male and female catkins. The male catkins are yellowish brown, and hang down from twigs. The female flowers are compressed into bud-like, erect catkins near the tips of branches. They have bright magenta-red thread-like styles that catch pollen released from the male catkins and scattered by wind. They bloom early to mid April, the earliest shrub to do so.

Beaked hazelnut (Corylus cornuta). Left: male catkins. Right: female catkin.

Sources:

Kershaw, Linda and Lorna Allen. 2025. Vascular Flora of Alberta: An Illustrated Guide. Second Edition. Self-published. Kindle Publishing.

Alberta Plant Watch. Nature Alberta.