Flower:

Male and female flowers are on separate plants (dioecious) in spike-like clusters (catkins) at the tips of short branchlets along 1 year old branches, emerging with the leaves. Male catkins are ½ to 1½ inches long, the flowers densely arranged, each flower with 2 purple to yellow-tipped stamens, the stamen stalk (filament) sparsely hairy near the base.

Female catkins are 1 to 2¼ inches long, the flowers densely to somewhat loosely arranged, oval-elliptic with a long beak, densely short-hairy, and on slender stalks up to 2 mm long. At the base of each male and female flower stalk is a yellowish-green to brown scale-like bract covered in short, curly, white and rusty-colored hairs.

Leaves and stems:

Leaves are alternate, 1½ to 3+ inches long, up to 1 inch wide, 2.5 to 5 times as long as wide, elliptic to oblong-elliptic, mostly widest near the middle, pointed at the tip, wedge-shaped to somewhat rounded at the base, with shallow, rounded teeth around the edges. The upper surface is dark green and shiny, the lower surface dull, paler green, sometimes with a few hairs near the base. Leaf-like appendages (stipules) at the base of the leaf stalk are absent or obscure.

New leaves are shiny, bright green or tinged red, hairless to sparsely hairy. New branchlets are hairless or soon becoming so, yellowish to reddish, becoming glossy red to red-brown the second year.

Stems are slender with smooth to slightly rough gray bark, up to 1½ inches diameter. Loose colonies are sometimes formed by a process known as layering, where a branch that touches the ground takes root and forms a new plant, detaching itself from the parent plant.

Fruit:

Fruit is a capsule 7 to 11 mm long, densely short-hairy, narrowly pear-shaped to conical with a long taper to the beak. The capsule splits into two halves when mature, releasing the cottony seed.

Notes:

There are over 20 species of Willows in Minnesota; Maccalla's Willow is one of the less common species, typically a medium to tall shrub found in high quality peatlands, calcareous fens and swamps in northwestern Minnesota. According to the DNR, its habitat, unmarred by human activity or invasive species, has become quite scarce and continues to decline. It was listed as a Special Concern species in 1996. It is recognized by its shiny red twigs; oblong-elliptic leaves to 3 inches long that are shiny, toothed, pointed at the tip, hairless or nearly so, pale green (not blue-green) on the underside; densely short-hairy fruit 7 to 11 mm long; male flowers have 2 stamens that are sparsely hairy near the base of the filament. Stipules are absent or obscure. Both male and female flowers are subtended by a yellowish-green to brown bract that is also short-hairy.

There are a few other Willow shrubs with red twigs and shiny leaves. Balsam Willow (Salix pyrifolia) has hairless fruit and proportionately broader leaves that are often heart-shaped at the base. Diamond-leaf Willow (Salix planifolia) has flowers that emerge before the leaves; fruit and bracts covered in long, silky, appressed hairs; leaves that are pale blue-green on the lower surface, leaf edges are often rolled under (revolute) and may be toothless. Autumn Willow (Salix serissima) leaves have a longer, more abrupt taper to the sharply pointed tip, fruit is hairless, and there are a few small glands at the tip of the leaf stalk near the blade.