Acer negundo L.

This is a small tree up to 60' tall with a trunk up to 3' across. It branches abundantly and has a broad well-rounded crown. On old trees, the gray bark forms deep curving furrows, while the gray bark of young trees forms furrows that are shallow and more erratic. Young branches are olive green and smooth with scattered white lenticels; less often, they are purple. The leaves develop oppositely from each other on young shoots; they are odd-pinnate with 3-7 leaflets. The leaflets are 2-4" long and about half as much across; they are more or less ovate in shape, coarsely dentate, and often shallowly cleft. Sometimes the terminal leaflets are moderately cleft to form 3 distinct lobes. The upper leaf surfaces are yellowish green, light green, or medium green, while the lower leaf surfaces are pale green and either hairless or slightly pubescent. Each leaflet has a short slender petiole at its base. The rachis (central stalk) of each compound leaf is hairless and often reddish. Box Elder is dioecious with male and female flowers on separate trees. Initially, dense clusters of drooping male and female flowers develop at about the same time, or a little ahead, of the leaves during early to mid-spring. Later, the clusters of female flowers elongate into drooping racemes. The male flowers have pedicels that are long, slender, and hairy. Each male flower consists of 5 small green sepals, no petals, and about 5 exerted stamens. The large anthers of the stamens are dark red initially, although they later turn brown before withering away. Each female flower has 5 greenish red sepals, no petals, and a pistil with a long style that is deeply forked. The flowers are wind-pollinated. Each female flower is replaced by a pair of samaras (winged seeds). Each samara is 1–1½" long. The samaras are initially green, but they later turn brown and often persist on the tree through the winter. The root system is woody. Vegetative shoots from underground runners are not produced. Cultivation

More info for the terms: caudex, root crown

off-site colonizer species;seed transported by wind;postfire years 1&2
off-site colonizer species;seed transported by animals;post-fire years 1&2
survivor species; on-site surviving root crown or caudex (possible)

General: Maple Family (Aceraceae): Boxelder is a native tree growing to 20 m tall, with broad rounded crown, usually developing a shallow, fibrous root system; bark light gray-brown with shallow fissures, becoming deeply furrowed; twigs slender, shiny green, usually glabrous but sometimes hairy. The leaves are opposite, 13-20 cm long, pinnately compound with 3(-5 or more) leaflets 5-10 cm long and 3-6 cm wide, long-pointed, coarsely toothed and often shallowly lobed. The flowers are yellow-green, about 5 mm long, the male (staminate) flowers fascicled, the female (pistillate) flowers in drooping racemes; most trees are either male or female (the species is essentially dioecious), but bisexual flowers occur on a few trees (technically polygamo-dioecious). Fruits are winged nutlets (samaras) in a pair, 2.5-4 cm long, clustered on long stalks. The common name refers to the resemblance of leaves to those of ash (Fraxinus). Boxelder, its other often used common name, refers to a resemblance to elder (Sambucus) and the use of the soft wood for box making.

Boxelder is unusual among American maples in having compound leaves. Apart from the opposite leaves, seedlings and young saplings of Boxelder bear a remarkable resemblance to poison ivy (Toxicodendron radicans) and are often mistaken for it by beginning naturalists.

Variation within the species:

Substantial variation occurs over the range of the species; numerous forms and varieties have been described, but only six varieties currently recognized (in some treatments, for example, see McGregor 1986). These are primarily distinguished by coloration of the branches, twig and fruit pubescence, and leaflet number.

Var. arizonicum Sarg. – Arizona and New Mexico

Var. californicum (Torr. & Gray) Sarg. – California

Var. interius (Britt.) Sarg. – midwest US into the western states

Var. negundo ­– the eastern half of the US, with naturalized western outlyers

Var. texanum Pax – south-central US

Var. violaceum (Kirchn.) Jaeger – north-central US and most of Canada

More info for the terms: root crown, tree

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.