ACER NEGUNDO
BOX ELDER, ASH-LEAVED MAPLE
The names "Box Elder" and "Boxelder Maple" are based upon the similarity of its whitish wood to that of boxwood and the similarity of its pinnately compound leaves with those of some species of elder. This is the only North American maple with compound leaves.
Leaves
Unlike most other maples (which usually have simple, palmately lobed leaves), Acer negundo has pinnately compound leaves that usually have three to seven leaflets. Simple leaves are also occasionally present; technically, these are single-leaflet compound leaves. Although some other maples have trifoliate leaves, only A. negundo regularly displays more than three leaflets.
The leaflets are about 5–10 centimetres (2.0–3.9 in) long and 3–7 centimetres (1.2–2.8 in), ovate or elliptic wide with coarsely serrate margins, base rounded to cuneate, glabrate above, usually pubescent beneath, acuminate. Leaves have a translucent light green colour and turn yellow in the fall.
The leaflets are about 5–10 centimetres (2.0–3.9 in) long and 3–7 centimetres (1.2–2.8 in), ovate or elliptic wide with coarsely serrate margins, base rounded to cuneate, glabrate above, usually pubescent beneath, acuminate. Leaves have a translucent light green colour and turn yellow in the fall.
Bark
The bark on its trunks is pale gray or light brown, deeply cleft into broad ridges, and scaly.
It often has several trunks and can form impenetrable thickets.
Branches are smooth, somewhat brittle, and tend to retain a fresh green colour rather than forming a bark of dead, protective tissue.
It often has several trunks and can form impenetrable thickets.
Branches are smooth, somewhat brittle, and tend to retain a fresh green colour rather than forming a bark of dead, protective tissue.
flowers
Unlike most other maples, A. negundo is fully dioecious and both a "male" and "female" tree are needed for either to reproduce.
Flowers: April, before the leaves, yellow green; staminate flowers in clusters on slender hairy pedicels one and a half to two inches long. Pistillate flowers in narrow drooping racemes. Calyx: Yellow green; staminate flowers campanulate, five-lobed, hairy. Pistillate flowers smaller, five-parted; disk rudimentary. Corolla: Wanting. Stamens: Four to six, exerted; filaments slender, hairy; anthers linear, connective pointed. Pistil: Ovary hairy, borne on disk, partly enclosed by calyx, two-celled, wing-margined. Styles separate at base into two stigmatic lobes. |
Fruit
The seeds are paired samaras, each seed slender, 1–2 centimetres (0.39–0.79 in) long, with a 2–3 centimetres (0.79–1.2 in) incurved wing; full size in early summer; they drop in autumn or they may persist through winter.
Borne in drooping racemes, pedicels one to two inches long. Key an inch and a half to two inches long, nutlets diverging, wings straight or incurved. September. Seed half an inch long. Cotyledons, thin, narrow. Seeds are usually both prolific and fertile. |
Winter buds: Terminal buds acute, an eighth of an inch long. Lateral buds obtuse. The inner scales enlarge when spring growth begins and often become an inch long before they fall.
ecology
This species prefers bright sunlight. It often grows on flood plains and other disturbed areas with ample water supply, such as riparian habitats. Human influence has greatly favored this species; it grows around houses and in hedges, as well as on disturbed ground and vacant lots.
Low woods and stream banks.
Low woods and stream banks.