Acer rubrum

Tree to 28 m tall, trunk to 1.5 m in diameter Leaves: opposite, stalked, light green above, pale green to whitish beneath, 5 - 15 cm long, 3.5 - 10 cm wide, toothed, shallowly three- to five-lobed, hairless to hairy beneath. Leaves usually turn red in fall, but may also be orange or yellow. Flowers: either male or female, found on the same (monoecious) or different (dioecious) plants, borne in clusters, red or yellow. Fruit: winged (samara), paired, borne in clusters, red to reddish brown or yellow, 1.2 - 2.6 cm long, with wings at 50 to 60 degree angles. Bark: dark gray, smooth when young, becoming shallowly ridged with flat scaly plates. Twigs: slender, green, becoming red to reddish brown, smooth. Terminal buds: dark red, 3 - 4 mm long, rounded, the scales fringed with hairs.

Similar species: Acer rubrum and Acer saccharinum are sometimes difficult to distinguish. Acer saccharinum has larger fruit with wider spreading wings, deeply lobed leaves that are more silvery white beneath, and twigs with an unpleasant odor when scratched. Acer rubrum var. rubrum is the most common variety of A. rubrum. It has few to no hairs on the lower leaf surface, which distinguishes it from other varieties. Acer x freemanii is a naturally occurring hybrid between A. saccharinum and A. rubrum. It combines the faster growth rate, adaptability to many soil types, and deeply lobed leaves of A. saccharinum with the red fall color and stronger branch structure of A. rubrum.

Flowering: mid March to early May

Habitat and ecology: Usually seen in swamps or bogs in the Chicago Region, but can adapt to diverse habitats such as swampy forests, upland slopes and dry-mesic forests. Seedlings establish in somewhat open woodlands and newly cleared areas.

Occurence in the Chicago region: native

Notes: Acer rubrum is often planted in landscapes for its red fruit, twigs, buds and fall color.

Etymology: Acer is derived from a Latin word meaning sharp, which refers to the hardness of the wood. Rubrum comes from the Latin word for red.

Author: The Morton Arboretum

Tree to 35 m; winter buds with 6-10 imbricate scales; young twigs red; lvs sharply but shallowly lobed, coarsely double-serrate, or with a few minor lobes, acute or short-acuminate, ±pubescent beneath when young; functionally dioecious; fls generally red, unisexual, short-pedicellate in fascicles from a cluster of lateral buds, opening much before the lvs; sep oblong, distinct, 1 mm, the pet a little narrower and longer, oblong-linear; ovary glabrous; mericarps mostly 2-4 cm; 2n=78, 91, 104, perhaps other nos. Swamps, alluvial soils and moist uplands, often as a successional tree; Nf. to se. Man., s. to Fla. and e. Tex., but missing from Io., most of Ill., and n. Mo. (Rufacer r.; R. drummondii; Acer carolinianum; A. stenocarpum) Morphologically, cytologically and ecologically variable, but indivisible.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.

From Flora of Indiana (1940) by Charles C. Deam

This and the preceding species [Acer saccharinum] are known in commerce as soft maples in contrast to the hard or sugar maples. Infrequent, except locally, in all parts of the state. In northern Indiana it is found both on gravelly ridges and in low ground, and rarely in bogs. In southern Indiana it is an infrequent tree on the ridges in most upland woods where it is associated with white oak, and in the "flats" in low, wet woods it may be frequent and is associated with sweet gum and beech. In the "flats" it grows to a large size and reproduces abundantly in wet, fallow fields. [Referring to var. drummondii:] I have this variety from only the cypress swamp in Knox County and from swampy woods in the southern part of Posey County.

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Indiana Coefficient of Conservatism: C = 5

Wetland Indicator Status: FAC

Diagnostic Traits: Leaves simple, palmately lobed and veined, the terminal lobe ca. 1/2 the length of the blade, the margins parallel toward the base or nearly so, the sinuses of principal lobes toothed; petioles with watery sap; flowers with inconspicuous petals; fruits mostly 2-4 cm.

Deam (1932): The red maple is not abundant enough in Indiana to be of any economic importance. It grows rapidly and should replace the silver maple for shade tree planting since its branches are not broken off as easily by ice storms and it more resistant to insect attack.