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Salix nigra Marsh. Black willow

Female catkins with flowers ready to receive pollen

Habitat

Black willow occurs naturally in New Brunswick only in the lower St. John River valley. Its most northerly occurrence is thought to be Burtt’s Corner on the Keswick River. It grows mostly in riverside areas and thus on low-lying, moist soils or swampy areas, and may be mixed with red and silver maple, white elm, and red ash. It is very shade intolerant, so is found only in relatively open conditions.

Tree in early spring

Form

Black willow is usually a small tree that grows up to 13 m in height and up to 50 cm in stem diameter, but in some parts of its large range, it may grow up to 20 m tall. The stems are often forked, and the crowns are broad and irregularly rounded. The wide-spreading branches tend to be brittle, so breakage is common.

Morphology

The leaves are simple and are borne fairly close together but alternately (in a single spiral) along the shoots. Each is 5–14 cm long, narrowly lanceolate and tapered to a long-pointed tip which tends to bend sideways. The leaf margins are finely and evenly toothed. Each leaf has a short petiole, at the base of which are two green, ear-like, toothed, persistent, stipules.

The buds, which are all lateral buds, are small, yellowish brown, shiny, pointed to somewhat flattened and round tipped, and each has a single cap-like scale. They are borne along thin yellowish-brown to reddish- or purplish-brown, shiny twigs that are slightly ridged below each tiny leaf scar. The pseudoterminal bud at the twig’s tip may be bent over the tiny scar formed when the shoot tip was lost.

Fruits (capsules) developing along a fruiting catkin, note the leaves below the base of the catkins

The flowers are borne in catkins, 2–7 cm long, that tend to be more or less erect, at the ends of new short leafy shoots during the blooming period. The trees are either male or female, so it is only on female trees that the catkins stay on the trees as the fruits develop from the flowers. The fruits, which are green, elongated, pear-shaped capsules, split open into two curled-back halves and shed their seeds in white, cottony masses in early summer.

Bark of stem, 15 cm in diameter

The bark is yellowish brown and slightly ridged when young. When old, it is dark brown or reddish brown to black with thick interlacing, flaky, flat-topped ridges, and deep furrows.

Notes

Black willow wood is diffuse porous, light in weight and color, soft and weak, but tends not to warp, check or splinter. Where reasonably plentiful, it is used for packing cases, barn floors, toys, and polo balls.

Black willow can be confused with crack willow (Salix fragilis L.), an introduced and naturalized tree species. The leaves of each are similar in shape, but those of crack willow have less uniform toothing, and are whitish rather than pale green on their undersides. They also lack persistent stipules and, in the spring, when stipules are still present, they are small and insignificant. The buds of crack willow tend to be gummy, narrow, and sharp pointed, and they are borne on yellowish-green to dark red twigs. The bark of crack willow is grey with narrow ridges.