Morus alba (White Mulberry)
Also known as:|
part shade, sun; moist to dry disturbed soil; woodland edges, fencerows, thickets, along streams, railroads|
May - June|
20 to 50 feet|
Wetland Indicator Status:|
GP: FACU MW: FAC NCNE: FACU|
MN county distribution (click map to enlarge):|
National distribution (click map to enlarge):|
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Male and female flowers are borne separately, usually on different trees (dioecious), in clusters called catkins, a few catkins emerging from buds along 1-year-old branches at about the same time as the leaves. Male catkins are ascending to pendulous in flower, ¾ to 2 inches long, green to yellowish, each flower in the cluster with 4 stamens.
Female catkins are erect to ascending and more compact, oval to short-cylindric, to 3/8 inch long, each flower with a somewhat flattened, oval green ovary and a whitish to reddish, 2-parted style. Cluster stalks on both male and female catkins are hairy.
Leaves and bark:
Leaves are alternate and simple, unlobed or irregularly 2 to 7-lobed, most lobes with rounded tips, the terminal lobe pointed or with abrupt taper to a pointed tip. The blade is generally egg-shaped in outline, 3 to 4 inches long, 1¼ to 3 inches wide, on a hairy stalk 1 to 2 inches long. Edges are coarsely toothed often with rounded teeth, the upper surface dark green, usually smooth and somewhat shiny, the lower surface lighter green with sparse hairs along veins or sometimes tufts of hairs in the vein axils. Three major veins radiate from the base where the stalk meets the blade.
Twigs are reddish to orange-brown with scattered, raised lenticels (pores). New growth is slightly hairy becoming hairless the second year with the lenticels flattening out and turning whitish. Bark is thin and somewhat rough, turning gray to gray-brown with maturity. Twigs and leaves exude a milky sap when cut.
Female catkins become nodding to pendulous fruit clusters, ½ to 1½ inches long, resembling elongated raspberries or blackberries. The color of fruit ranges from white to pink to red, usually turning purplish-black when mature but sometimes remaining white.
White Mulberry is native to China where it is the favored food of silk worms. It was initially introduced to North America in the 1600s in the first of several failed attempts to establish a silk industry here. A fast growing tree that tolerates a variety of soil and moisture conditions, many cultivars have been bred and planted globally as a shade tree or ornamental and for its sweet, edible fruit. It escapes cultivation primarily via birds, which love the fruits and spread the seed far and wide; it has become a pest plant in parts of most countries where it has been introduced, crowding out natives. It even pops up in my own suburban lawn occasionally but is promptly removed.
White Mulberry is often confused with the native Red Mulberry (Morus rubra). While the leaf shape of both species can be quite variable, Red Mulberry usually has (mostly) unlobed leaves that are dull and somewhat rough on the upper surface and hairy on the lower, while White Mulberry leaves are (mostly) 3 to 7-lobed, smooth and shiny on the upper surface, hairy only along the veins on the lower, and tend to be smaller (max 4 inches long vs. 7 inches). White Mulberry twigs and bark also tend to be more orange than Red Mulberry. The two species are known to hybridize, which complicates matters, and the hybrid has been recorded in Minnesota scattered across our southern counties and as far north as Sherburne county (see the county distribution map above). The hybrid is not well-documented but is likely intermediate between the two.
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White Mulberry tree
White Mulberry trees
White Mulberry crown/branching
bark of young tree
lower leaf surface only hairy along the veins
leaves in fall color
Have you seen this plant in Minnesota, or have any other comments about it?