Trees of Wisconsin

Acer negundo L.
box elder; ashleaf maple
Family: Aceraceae
tree leaf buds trunk twig female flower male flower fruit

The leaves of Acer negundo are compound and opposite and are often composed of 5 (occasionally 7) leaflets. Leaves of seedlings and less prosperous trees often have 3 leaflets, in which case they may be mistaken for Poison Ivy, the leaves of which are alternate. The twigs of Acer negundo are usually purplish, or green with at least a tinge of purple and when young are heavily glaucus. As the twigs age this glaucus covering is lost and the area so covered may be inconspicuous late in the growing season and on trees for which the annual growth increment is small. The winter buds are covered by a dense growth of appressed whitish hairs. Leaf scars, are broadly "U" shaped and meet at their edges in a raised point. Trees are highly prone to sprouting along the trunk where damaged, and the stumps of cut trees resprout vigorously resulting in multiple-stemmed growth forms. The shape of individual trees varies greatly, the most extreme forms due to multiple injuries over a period of years or to repeated cutting.

Acer negundo is a dioecious species, meaning that each individual tree is either a male or a female (each flower has only male or female parts and each tree has only one of these flower types). The female trees tend to keep the samaras (fruit) well into the winter or even into the next spring.

Acer negundo is a native species in Wisconsin and was apparently largely restricted to wet, deciduous forests in the southern portion of the state before European settlement. It is still very common there, perhaps more so because it is well adapted to the many highly disturbed forests presently found in such sites in Wisconsin. It has also become a common invader of a wide variety of disturbed upland sites, including abandoned fields, open ground in cities, rights-of-way and fence rows. Where large populations are present in the area, seedlings can be found in nearly any habitat except for the wettest and driest. It is occasionally found virtually throughout Wisconsin and into the upper peninsula of Michigan, but in the north it is largely restricted to man-made disturbances near road crossings of streams, and disturbed urban sites. It is considered a weedy species in the current landscape by some observers, but pales as an invasive species in comparison to the Buckthorns (Rhamnus species). It has sometimes been used as a "default" street tree (not often now) and may be beneficial in sites where its fast growth and resistance to damage are desirable.


known Wisconsin distribution


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