Black Willow is a large, but short-lived, native deciduous tree growing 60 to 80 feet high and 1-1/2 to 2-1/2 feet in diameter, with a trunk (or several trunks) that usually leans, with a narrow or irregular crown and upright branches. The largest Black Willow known in Minnesota is in Washington County - 91 feet high, 75 foot crown spread, 315 inches in circumference, scoring 425 points. That tree is also the national champion Black Willow.
The bark is brown to gray-black, fairly smooth when young, but with age becoming deeply fissured into forking scaly ridges.
Twigs are slender, easily detached at the base with a clean break, orange-brown to brown with small appressed buds covered with one scale. The terminal bud is lacking. Leaf scars are crescent shape. New shoots are green.
Leaves are alternate, narrowly lance-shaped 3 to 5 inches long and only up to 3/4 inch wide, often somewhat curved to one side, hairless with a fine serrate margin, narrowed at the base and tapered to a long pointed tip. The top side is a shiny dark green, but underside paler. Leaf stipules may or may not be present.
Flowers: Black Willow is dioecious, that is, the male and female flowers are on different plants. Both are borne in catkins near the ends of leafy twigs in spring, after the leaves. Male catkins are yellow to greenish-white, 1 to 3 inches long and found in various positions - ascending, drooping or slightly curved. The numerous florets have a small bract and 4 to 6 (3 to 7) stamens whose filaments have fine hair; anthers are yellow. Female catkins are shorter, greenish, and have a pistil with a pair of stigmata.
Seed: Fertile female flowers form a 3/16 inch long pointed ovoid capsule, yellow-green at first, then reddish-brown, containing 12 to 15 very small seeds which have a hairy white pappus attached. These capsules split in two sections at maturity and the two sides curl backward in mid-summer to allow the seeds to be wind dispersed by means of their feathery pappus. Trees can start producing seed at 10 years of age. Seeds can germinate immediately.
Habitat: Black Willow has a shallow, widely spreading root system. It prefers full sun in wet to moist soils but will tolerate dry soils and produce a less vigorous plant. The twigs, which snap off so readily will set roots if they are in damp soil.
Names: The genus name for the willows, Salix, is the Latin name for a willow and means 'to leap' referring to the fast growth in the spring. The species name, nigra, is Latin for black. The author name for the plant classification from 1785 - ‘Marshall’ is for Humphry Marshall (1722-1801), American Botanist, who published - Arboretum Americanum: The American Grove, an Alphabetical Catalogue of Forest Trees and Shrubs, Natives of the American United States (1785).
Above: 1st and 2nd photos - Black Willow has an irregular crown, upright branches and a trunk that is usually leaning. 3rd photo - Older bark is deeply fissured into forking scaly ridges.
Below: 1st and 2nd photos - Leaves are long and narrow with a serrated edge, somewhat curved to one side. Stipules (shown 1st photo) may be present but wither away during the season. 3rd photo - Male and female flowers are in catkins on different plants appearing with or just after the leaves. Here are the female catkins.
Below: 2nd photo - A female catkin showing the long green pistils and paired yellow stigma.
Below: 1st photo - The male catkin of Black Willow with the stamens exserted. The small covering bract has dropped away at this stage. 2nd photo - Twigs are slender, easily detached at the base, orange-brown to brown with small and appressed buds covered with one scale. The terminal bud is lacking. Leaf scars are crescent shape.
Below: Fertile female flowers form a 3/16 inch long pointed capsule, reddish-brown at maturity, containing 12 to 15 small seeds which have a hairy white pappus attached.
Above: This gall in the shape of a pine cone, appears on willow stems and confuses many because of its resemblance to a pine cone. In the summer a small fly called a gall gnat midge (Rabdophaga strobiloides) deposits an egg on the stem. The new larva secretes a substance on the stem which causes the willow to go into overdrive building a multi-layered chamber composed of hardened material that would have been leaves had stem growth not been arrested.
The development of the gall is seen in the 1st photo and the winter-hardened version is shown in the 2nd photo, in which snugly resides the larva, which will metamorphose into a gnat when warm weather comes again.
Below: If you split one of these cones open you will find the small pink larva resting inside unless some of its wasp-like parasites have invaded the chamber.
Notes: Black Willow is not indigenous to the Garden. Eloise Butler planted the first specimens in May 1909 with stock received from the Park Board Nursery which in that year had just relocated to Glenwood Lake near the Garden. By the time of Martha Crone's 1951 Garden census, they were no longer present. Black Willow is native to the eastern half of North America except for the Canadian Maritime Provinces. It is one of the most widespread willow species, reaching as far west as Nebraska to Texas in the US. Within Minnesota, it is found in about 1/3 of the counties, with most being in the eastern half of the state. 22 members of the Salix genus are native to Minnesota along with 2 introductions. Hennepin County is known to have 13 of those.
Uses: Black Willow is the only commercially important willow in North America. The wood is light, straight-grained with good tensile strength. It has been used in millwork, furniture, boxes, barrels and for pulpwood. Its root system makes it valuable for erosion control in riparian areas. The bark of Black Willow has been boiled in water and the resulting fluid used as a tonic, an astringent and by the mid-19th century salicylic acid was obtained from the bark to use for pain reduction and fever reduction. Today aspirin is synthetically produced but the formula was derived from the willow.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"