Acer negundo (Boxelder)
|Also known as:||Ash-leaf Maple, Manitoba Maple|
|Life cycle:||perennial woody|
|Habitat:||part shade, sun; average to moist; river bottoms, lakeshores, windbreaks, woods|
|Bloom season:||April - May|
|Plant height:||30 to 50 feet|
|Wetland Indicator Status:||GP: FAC MW: FAC NCNE: FAC|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Male and female flowers are on separate trees and appear before or as the leaves emerge in early spring. Male flowers hang in clusters on the outer buds of branches; 3 to 5 stamens at the tip of a slender, hairy stalk, ½ to 1¾ inches long. Immature anthers (stamen tips) are often deep maroon colored.
Leaves and bark:
Leaves are opposite and compound, typically with 3 to 5 leaflets, occasionally 7. Leaflets are mostly lance-elliptic with an abrupt taper to a pointed tip, up to 3¾ long and 2¼ inches wide, smooth to coarsely toothed around the edges, on stalks that are typically smooth but may be covered in short hairs. The end leaflet is typically largest and often shallowly lobed in 3 parts, sometimes deeply so. Surfaces are mostly smooth, the underside is paler than the upper surface and sometimes sparsely hairy. Leaves turn a dull yellow in fall.
The trunk can be up to 4½ feet in diameter at breast height (dbh), though 3 feet is more typical for a mature tree. Bark is medium to coarse, light brown to gray-brown with blocky, vertical ridges and furrows. Twigs are smooth or densely hairy on newest growth, olive green in summer, more blueish to purple in winter. The crown is irregular, often with low spreading branches wider than the tree height.
Boxelder is common and widespread throughout Minnesota, except in the Arrowhead. Minnesotans often do not recognize it as a maple, due to its compound leaves, but in fact, in parts of Canada it goes by the name “Manitoba maple”. It was once quite popular as a farmstead, windbreak and yard tree due to its cold hardiness, drought tolerance and ease in transplanting, It can be a very aggressive colonizer on disturbed sites, as many gardeners have observed from its heavy seed load. The seeds can also attract large numbers of the seed eating boxelder bug. But its wood is soft and brittle, highly disposed to limb breakage and heart rots, even in fairly young trees. Perhaps a tree that can appear to be busy dying the day you plant it? It resprouts readily from stumps and broken limbs and can live to nearly 100 years old. There are 6 recognized varieties, primarily distinguished by branch color, hairiness, and number of leaflets; 2 vars are found in Minnesota: var. negundo, the most common, has hairless twigs and leaf stalks; var. interius has hairy twigs and leaf stalks. The compound leaves may be mistaken for an Ash species, but Ash leaflets are more uniform in shape and never lobed. Early growth has also been mistaken for Poison Ivy (Toxicodendron rydbergii) but the opposite leaves of Boxelder should distinguish it.
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Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk taken in Anoka and Ramsey counties.
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