|Acer negundo subsp. var.||Box elder, Box elder maple, Manitoba maple|
Acer negundo is a species of maple native to North America. Box Elder, Boxelder Maple, and Maple Ash are its most common names in the United States. Other variant names -- some of which are regional - include Ash Maple, Ash-leaf Maple, Black Ash, California Boxelder, Cutleaf Maple, Cut-leaved Maple, Negundo Maple, Red River Maple, Stinking Ash, Sugar Ash, Three-leaved Maple, and Western Boxelder. In Canada it is commonly known as Manitoba Maple and occasionally as Elf Maple. In Russia it is called American Maple (Template:Lang-ru) as well as Ash-leaf Maple (Template:Lang-ru).
Acer negundo is a small, usually fast-growing and fairly short-lived tree that grows up to 10-25 m tall, with a trunk diameter of 30-50 cm, rarely up to 1 m diameter. It often has several trunks and can form impenetrable thickets.
The shoots are green, often with a whitish to pink or violet waxy coating when young. Branches are smooth, somewhat brittle, and tend to retain a fresh green colour rather than forming a bark of dead, protective tissue. The bark on its trunks is pale gray or light brown, deeply cleft into broad ridges, and scaly.
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 (such as A. griseum, Acer mandshuricum and the closely-related A. cissifolium) have trifoliate leaves, only A. negundo regularly displays more than three leaflets.
The flowers are small and appear in early spring on drooping racemes 10-20 cm long. The seeds are paired samaras, each seed slender, 1-2 cm long, with a 2-3 cm incurved wing; they drop in autumn or they may persist through winter. Seeds are usually both prolific and fertile.
Unlike most other maples, A. negundo is fully dioecious and both a "male" and "female" tree are needed for either to reproduce.
- 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.
- 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, exserted; 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: Maple keys, full size in early summer. 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.
|Standard Cyclopedia of Horticulture|
Acer negundo, Linn. (Negundo fraxinifolium. Nutt. N. aceroides, Moench. Rulac Negundo, Hitchc.). Ash-leaved Maple. Box Elder. Fig. 101. Large tree, 70 ft.: lvs. pinnate; lfts. 3-5, ovate or oblong-lanceolate, coarsely serrate or 3-lobed, mostly glabrous, 2-5 in. long: fls. before the lvs.; staminate fls. in pendulous corymbs, pistillate fls. in pendulous racemes. E. N. Amer. S.S. 2:96. Michx. Hist. Arb. 2:18. H.T. 336.— Large, rapid-growing tree of spreading habit, thriving best in moist and rich soil. Much prized in the W., where it withstands cold and dryness. Largely used for shelter-belts and for planting timber-claims. Var. californicum, Sarg. (A. californicum, Dietr. Negundo californicum, Torr. & Gray). Branches pubescent when young: lfts. 3, of firmer texture, densely pubescent beneath: fr. not constricted at the base. W. N. Amor. S.S. 2:97. Nutt. N. Amer. Sylv. 2:72. Var. pseudo-californicum, Schwerin (A. californicum, Hort. A. Negundo var. californicum, Kirchn.). Branches green, bloomy; of vigorous growth. Var. violaceum, Kirchn. (A. californicum, Hort.). A vigorously growing form: branches purplish with glaucous bloom or finely pubescent when young. Var. argenteo-variegatum, Bonamy. Lvs. with broad white margin. Probably the most effective of all variegated hardy trees. F.S. 17:1781. Gn. 68, p. 402 (habit). G. 2:37; 11:97 (habit). Var. aureo-variegatum, Booth (var. aureo-maculatum, Schwerin). Lvs. spotted with yellow. Var. aureo-marginatum, Dieck. Lvs. with yellow margin. Var. auratum, Spaeth (var. californicum aureum, Hort.). Lvs. yellow. R.B. 1906:197. Var. crispum, G. Don. Lfts. curled. These horticultural varieties may be grafted on common box elder seedlings. Box elder also grows from hardwood cuttings, like the grape. Two new forms have been recently described as new species by Britton: A. interior, distributed from Alberta and Mont, to Ariz, and New Mex. (B.T. 655), and A. Klngii (B.T. 656), from Utah; they are closely allied to var. californicum, but differ in their glabrous foliage; in the first the wings of the samara are adnate to the nutlet only to or above the middle; in the second the wings reach the point of union of the nutlets.CH
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- 'Auratum' - yellowish leaves with smooth undersides
- 'Aureomarginatum' - creamy yellow leaf margins
- 'Baron' - Hardier & seedless variety
- 'Elegans' - distinctively convex leaves
- 'Flamingo' - pink and white variegation (very popular)
- 'Variegatum' - creamy white leaf margins
- 'Violaceum' - younger shoots and branches have blueish color
A. negundo is often discussed as being comprised of three subspecies, each of which was originally described as a separate species. These are:
- A. negundo subsp. negundo is the main variety and the type to which characteristics described in the article most universally apply. Its natural range is from the Atlantic Coast to the Rocky Mountains.
- A. negundo subsp. interius has more leaf serration than the main species and a more matte leaf surface. As the name interus indicates, its natural range of Saskatchewan to New Mexico is sandwiched between that of the other two subspecies.
- A. negundo subsp. californicum has larger leaves than the main species. Leaves also have a velvety texture which is essential to distinguish it from A. negundo subsp. negundo. It is found in parts of California and Arizona.
Some authors further subdivide subsp. negundo into a number of regional varieties but these intergrade and their maintenance as distinct taxa is disputed by many. Even the differences between recognized subspecies are probably a matter of gradient speciation
Finally, note that a few botanists treat Boxelder Maple as its own distinct genus (Negundo aceroides) but this is not widely accepted.
- ↑ Community trees of the Prairie provinces - Canadian Forest Service
- ↑ 2.0 2.1 2.2 2.3 van Gelderen, C.J. & van Gelderen, D.M. (1999). Maples for Gardens: A Color Encyclopedia.
- ↑ Cite error: Invalid
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