Acer negundo

Western Boxelder

Sapindaceae

The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Viridiplantae (Green plants). Superdivision - Embryophyta. Division - Tracheophyta (Vascular plants). Class - Magnoliopsida. Order - Sapindales. Family - Sapindaceae. Genus -Acer L. Species - Acer negundo Linnaeus

Ecology: Boxelder is widespread in riparian and palustrine communities throughout most of the contiguous United States. Its range extends from New Jersey and central New York west through extreme southern Ontario, central Michigan, northern Minnesota, central Manitoba, central Saskatchewan, southern Alberta and central Montana, eastern Wyoming, Utah, and California; and south to southern Texas and central Florida. It is also local in New Hampshire, Vermont, Massachusetts, Connecticut, Idaho, and Nevada. Boxelder has been naturalized in Maine, southern Quebec, New Brunswick, Nova Scotia, Prince Edward Island, and in southeastern Washington and eastern Oregon. Varieties of boxelder occur in the mountains of Mexico (Nuevo Leon, San Luis Potosi, and south to Chihuahua) and in Guatemala. Also widely cultivated and naturalized n China

Identification

Western Boxelder (Acer negundo), also known as California Boxelder and Boxelder Maple, has yellowish brown or gray-brown bark. Trees grow to 20 m tall and are dioecious. Branchlets glabrous, those of present year green, older ones yellowish brown; winter buds small, scales 2(or 3) pairs. Leaves deciduous; leaf blade 10-25 cm, papery, pinnate; petiolules 5-7 cm, pubescent, glabrescent; leaflets 3-7(-9) per petiole; leaflet blades ovate or elliptic-lanceolate, 8-10 2-4 cm, base rounded or truncate, margin entire or with 3-5 teeth, apex acute. Pistillate inflorescence pendulous, racemose or compound racemose, axillary from leafless buds, 15-50-flowered. Staminate inflorescence usually a cluster of 4 flowers. Flowers 4-merous. Petals and disk absent. Stamens purplish, 4-6. Ovary glabrous. Samaras brownish yellow; nutlets convex, glabrous; wing including nutlet 3-3.5 cm 8-10 mm, wings spreading acutely or nearly erectly.

Threats

Fire ecology: Boxelder grows on moist bottomland sites which are seldom subject to burning. This thin-barked species is injured by fire [50], but how it regenerates following fire is not known. Boxelder produces large yearly crops of wind-dispersed seeds which germinate on a wide variety of soils; this is most likely boxelder's primary fire survival strategy. This tree also sprouts from the exposed roots, root crown, or stump following top-killing mechanical damage [1,13,19,38], and it is likely that boxelder would sprout following fire severe enough to girdle or top-kill the adult tree.

Fire effects: Van Dersal reports that this thin-barked species is injured by fire. Boxelder most likely reestablishes following fire via wind-dispersed seeds. It may also sprout from the roots, the root collar, or stump if girdled or top-killed by fire.

Pests and pathogens: A number of insect pests or fungal diseases have been noted on A. negundo (e.g. Gilman and Watson, 1993) but few have been reported to adversely affect the species. It is susceptible to heartrot and some insect pests but these rarely kill it. The boxelder bug, Boisea trivittata (Say) feeds primarily on seed-bearing trees by sucking sap from the leaves, tender twigs and developing fruits, and although they cause little damage they are a nuisance in dwellings (Vail et al., 2002)

Reproduction

Seed Production and Dissemination - Boxelder reproduces both sexually and asexually. Large seed crops are produced each year. Boxelder flowers from March through May with or before the appearance of the leaves. The fruit, a winged samara, ripens from September through October and is dispersed from September through March. Seeds persist through the winter; they are dispersed by wind or by birds and squirrels. Wind will carry these winged seeds up to 100 yards across a snow surface. Boxelder establishes by seed under a wide range of conditions: immediately after disturbance on moist disturbed soil, along riverbanks, and in areas with heavy cover and medium to heavy competition.

Seedling Development - Boxelder produces large, yearly crops of wind-dispersed seeds which germinate on a wide variety of soils.

Vegetative Reproduction - Vegetative reproduction is common on damaged plants of this species. New shoots will appear on exposed or injured roots. Although this species will produce abundant sprouts after disturbance, the primary method of reproduction is through seed, due to the quantity produced each year and the facility of its distribution.

Species Distribution

Citation

Invasive Species Compendium
Acer negundo (Box Elder).

USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.

USFS Plant Database
Habeck, R. J. 1992. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.

Integrated Taxonomic Information System
Acer negundo L.

Burke Museum of Natural History and Culture
Burke Museum. 2016. University of Washington.