Willow Family Salicaceae

Arctic willow, Salix arctica;
note the fuzzy male catkins.

The willow family is composed of trees and shrubs belonging to two genera: the poplars, Populus, and the willows, Salix. In both genera the flowerheads are called catkins short columns of tiny, densely crowded flowers that lack petals and are either male or female. Male catkins produce pollen, while female catkins yield seeds. One plant within a species is entirely unisexual, bearing only female or male catkins, not both. What is generally referred to as a pussy-willow is actually the male plant of a number of species, bearing hundreds of very furry male catkins.

Two poplars, balsam poplar, Populus balsamifera, and trembling aspen, P. tremuloides, occur just at the very edge of the treeline in the Low Arctic. Balsam poplar is the only broad-leaved hardwood in the Arctic to have deeply furrowed bark. It grows farther north than trembling aspen on the gravelly shores of lakes and north-flowing rivers. Trembling aspen has smooth, chalky bark and is named for its weak, pliable leaves which "tremble" in the slightest breeze. In September, its leaves turn a deep, golden yellow colour, a stark contrast to the more dominant evergreen trees and, at its northern limit, trembling aspen is reduced to a low-growing shrub.

Arctic willow, S. arctica (male).

The Salix genus is taxonomically complex and represented by more than 22 very similar species in the Arctic. However, three species arctic willow, S. arctica, net-veined willow, S. reticulata, and least willow, S. herbacea are easily identified. Larger willow species provide an important food source twigs, young leaves, bark, and buds for many arctic animals, including caribou, muskoxen, hares, lemmings, ptarmigan, and other birds. The young leaves and buds of several species are collected by the Inuit for food and are reportedly high in vitamin C.

Arctic willow is widespread throughout Canada's Arctic and is the farthest reaching species in the willow family, growing abundantly at the northern tip of Ellesmere Island. Though lacking brightly coloured flowers, the arctic willow still attracts plenty of pollinating insects because of its plentiful supply of nectar within its catkins. They are also well adapted to life in the Arctic because their transparent "fuzz" acts like tiny greenhouse windows. When the sun is shining, female catkins soak up the rays and warm to 4 or 5oC above the outside temperature. Male catkins, in spite of having more "fur", fall short by about 1oC.

Arctic willow, S. arctica (male).

Net-veined willow grows very low, almost creeping along the ground. Its leaves are unique among the willows and are the characteristic feature of this shrub the leaf veins form a network of deep grooves, hence its common name.

Last, and definitely "least", is the least willow, an eastern Arctic species that grows on damp moss. Short side branches protrude from the horizontal stems and each is tipped with a pair of tiny, opposite, oval leaves. A closer look reveals that each leaf one bigger than the other is notched at its tip and has rounded teeth along its margin. At the right time of year, miniature catkins can even be seen between the leaves.

This net-veined willow (male), S. reticulata, shows how the plant was named – the leaf veins form a network of deep grooves.