Native to a vast expanse of the eastern United States, the red mulberry tree (Morus rubra) is typically found growing in rich, moist soils. From Massachusetts to Michigan and Minnesota south to Texas and most of Florida, the mulberry tree often is seen growing as an understory tree in mixed woodlands or at the sunny edges of forests. It grows in USDA hardiness zones 4 through 9 where winter low temperatures drop no colder than minus-30 degrees Fahrenheit.
Depending on soil moisture and fertility, the red mulberry tree grows 40 to 60 feet tall and 40 to 50 feet wide. It grows with a singular trunk that is short--carrying the first branches rather low to the ground and having somewhat drooping branch tips. The leafy canopy is upright and broad but abstractly oval with irregular branching.
The bark of young trees or saplings is orange-brown, especially when wet after rains, according to Virginia Tech University's plant database. More mature trees have trunks and branches that are covered in a grayish brown bark that is thin with irregular ridges in long strips.
The twigs of branches exude a milky sap if snapped. The foliage ranges in size from 3 to 8 inches in size and the leaves vary in shape from being simply tapering ovals to almost heart shapes or deeply lobed to resemble the leaves of a sassafras. Regardless of leaf size or shape, they are papery, deep green in color and glossy with soft, slightly fuzzy undersides. Edges of leaves are also lined in tiny serrations. The leaves are arranged in an alternating pattern on the branches. In autumn, the leaves turn clear yellow before dropping off.
Red mulberry trees are either male or female, according to Virginia Tech University. The tree's sex is determined by the flower encountered in spring, appearing any time from March (in the American South) to June (near the Canadian border). The flowers are small and pale green and tiny clusters in pendulous catkins. Male catkins are 1 to 2 inches long and have inconspicuous blossoms with stamens. Female catkins are no more than 1 inch long and have tiny blossoms that only have pistils with ovaries.
Only female-gendered red mulberry trees develop their pollinated flowers into fruits. When immature, the fruits (called drupes) look like white to pale green raspberries on stems dangling from the tree twigs. They first ripen to red (very sour in flavor) and then turn dark purplish to black (sweet and juicy). The fleshy fruits are full of tiny seeds.
The common or white mulberry (Morus alba) is native to China but is a weedy tree species that was introduced into North America. This tree has spread and naturalized across much of eastern North America. It naturally interbreeds with the native red mulberry tree to create seedlings with a blend of characteristics of both parents, making them difficult and confusing to absolutely identify.