Salix nigra is a tree to 20 m tall; 50 cm dbh; lives to about 55 years; shallow rooted, may form adventitious roots low on trunk; trunks 1-4, leaning, colonial from root sprouts; twigs yellowish, slightly hairy when young. Stipules to 1.2 cm, semi-cordate, pointed, toothed; leaf
Leaves alternate, stalk 0.7 cm, hairy, glandular at top. Blade nearly linear, 6-10 cm long, 1-1.5 cm wide, tip long-pointed, base rounded, green on both sides (slightly paler below), margin finely glandular-toothed, drooping, marginal vein continuous.
Flowers with sexes on different plants (dioecious), in catkins ca 5 cm, drooping, stamens of male flowers; blooms April-May, insect and wind pollinated (flowers have nectar).
Fruit narrow capsules, 0.6 cm, splitting open to release tiny, hairy seeds June-July, dispersed widely by wind and water. Seed killed by drying after 24 hrs, germinates same season, needs wet open soil and full sun. Seedlings grow rapidly.
Wetland status: FACW+.
Frequency in NYC: Common.
Habitat: Pioneer on wet to moist soil in open habitats, fill, flood plains, stream banks. Tolerates soil pH 4.8-8 (USDA, NRSC 2010). Tolerant of flooding, drought, soil compaction. Moderately salt tolerant. Extremely intolerant of shade, index 1.4.
Notes: Leaves eaten by small, oval, shiny black beetles, Plagiodera versicolora (the imported willow leaf beetle, Coleoptera, Chrysomelidae) (see S. discolor), the willow sawfly (Nematus ventralis, Hymenoptera, Tenthredinidae). Adults emerge in spring and lay eggs in tissue of young leaves. The larvae feed on leaves and grow to 1.8 cm; they are black to greenish-black with pale yellow spots along their sides. Larvae of butterflies and moths (Lepidoptera), that eat black willow include: the tiger swallowtail butterfly (Papilio gaucus, Papilionidae), mourning cloak butterfly (Nymphalis antiopa, Nymphalidae); red-spotted purple butterfly, Limenitis arthemis astyanax; Nymphalidae), viceroy butterfly (L. archippus, Nymphalidae); dreamy dusky wing butterfly (Erynnis icelus, Hesperiidae); luna moth, (Actias luna, Saturniidae); Io moth, (Automeris io, Saturniidae), polyphemus moth (Antheraea polyphemus, Saturniidae), big poplar sphinx moth, Pachysphinx modesta, Sphingidae); American dagger moth (Acronicta americana, Noctuidae); giant leopard moth (Ecpantheria scribonia, Arctiidae), black-etched prominent (Cerura scitiscripta, Notodontidae), the fall webworm (Hyphantria cunea, Arctiidae), large tolype moth (Tolype velleda, Lasiocamidae) and the non-native gypsy moth (Lymantria dispar, Lymantriidae) (Tallamy 2003). Leaves are also attacked by both adults and larvae of the willow flea weevil, Rhynchaenus rufipes. The adult is a small, black snout beetle (Coleoptera, Curculionidae) about 0.2 cm long, elliptic, with reddish yellow legs and antennae, and large eyes. It emerges in spring and chews tiny holes in new leaves and shoots. Larvae mine leaves starting in early summer leaving pale grayish, skeletonized blotches. Another generation of adults causes more tiny holes in late summer. As weather becomes cool adults may congregate on the sides of buildings. The willow shoot sawfly,
Janus abbreviatus (Hymenoptera, Cephidae), injures twig tips by girdling them as eggs are laid under the bark in May and June. Larvae kills the twigs by boring downward through the pith, eating as they go and packing the hollowed stem with fecal material (frass). It pupates and overwinters in the stem. Borers often transmit fungal infections such as willow blight (Pollaccia saliciperda). Yellow bellied sap suckers feed on sap by pecking holes in bark in a pattern of rings around branches or trunks, leaving trees vulnerable to fungal infections. Carpenter ants (Camponotus pennsylvanicus and others) can hollow out interior of older trees (Borror and White 1970; Burns and Honkala 1990; Drooz 1985; Johnson and Lyon 1991; Sinclair et al. 1987). A host tree of the Asian longhorn beetle, Anoplophora glabripennis (see Norway maple).