Flower:

Male and female flowers are on separate plants (dioecious) in spike-like clusters (catkins) at the tips of very short branchlets or from buds along 1 year old branches, emerging before the leaves. Male catkins are oval-elliptic to nearly round, ½ to 1½ inches long, the flowers tightly packed, each flower with 2 yellow-tipped stamens.

Female catkins are ½ to 2½ inches long, the flowers crowded on the spike, narrowly conical with a long beak, densely covered in silky hairs, stalkless or nearly so, the stalks not more than 1 mm long. At the base of each male and female flower stalk is a tiny, dark brown to blackish, scale-like bract densely covered in long, straight hairs.

Leaves and stems:

Leaves are alternate, ¾ to 2½+ inches long, up to 1 inch wide, 2.5 to 4.5 times as long as wide, oblong-elliptic to narrowly urn-shaped, widest near the middle or sometimes near the tip, rounded to pointed at the tip, wedge-shaped to somewhat rounded at the base, irregularly toothed around the edges often with shallow, rounded teeth, sometimes toothless. The upper surface is hairless, medium to dark green and glossy, the lower surface pale blue-green and mostly hairless. At the base of the leaf stalk may be a pair of tiny, leaf-like appendages (stipules), green or brownish, but are often obscure.

New leaves are hairless or sparsely silky-hairy on the lower surface, and are red-tinged or yellowish-green. The main veins are straight to slightly curved upward from the midvein and evenly spaced. New branchlets are hairless to sparsely hairy and green, becoming glossy red to red-brown and hairless by the second year.

Stems have smooth to slightly rough, gray-brown to greenish bark and can reach 3 inches diameter. Loose colonies may form 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:

The spike elongates slightly as fruit matures, but it is common for many flowers in a catkin to not produce any fruit. Fruit is a capsule 2.5 to 6 mm long, yellowish when mature, covered in appressed silky hairs, conical to horn-shaped, the beak straight to slightly curved. The capsule splits into two halves when mature, releasing the cottony seed; this happens before leaves are fully mature.

Notes:

There are over 20 species of Willows in Minnesota; Diamond-leaf Willow is typically a mid-sized to large, multi-stemmed shrub, averaging about 6 feet tall. It is common to occasional in a variety of wet places including lake and pond margins, swamps, wet meadows and the occasional wet ditch, as well as on the rocky north shore of Lake Superior. It is recognized by the shiny red twigs; flowers emerging before the leaves; fruiting catkins with silky hairy capsules that are stalkless or nearly so, and frequently have aborted fruit; leaves widest near the middle or near the tip, glossy on the upper surface, pale blue-green below, mostly hairless, the main veins numerous, curving up from the midvein and evenly spaced with minor veins more obscure; male flowers have 2 stamens. Both male and female flowers are subtended by a tiny, dark brown to blackish bract covered in long, straight, white hairs.

The leaves most closely resemble those of Pussy Willow (Salix discolor), which has similar venation but the main veins are irregularly spaced and fewer in number, its fruiting catkins are more loosely arranged, each fruit on a stalk 2 to 3 mm long; leaves are duller green on the upper surface, twigs are dull yellowish to reddish-brown, and it sometimes forms a small tree. Balsam Willow (Salix pyrifolia) has shiny red twigs and glossy leaves like Diamond-leaf Willow, but its leaves are more sharply pointed at the tip, often heart-shaped at the base, have a network of prominent veins, and fruit is hairless.