Native to North America, red mulberry (Morus rubra, Moraceae) is most commonly found in moist areas along streams and forest borders (Kershner et al. 2008). A number of them grow along the edge of a particular floodplain forest here in southeast Michigan. When I visited them a couple of weeks ago they were loaded with large numbers of their conspicuous aggregate fruits. These “berries” start out white and then turn red and ultimately purple as they ripen. Similar to blackberries, they’re quite juicy and sweet. Unsurprisingly when I visited them again today the berries were all picked clean by birds, insects, and other animals.
It’s important to contrast red mulberry with white mulberry (Morus alba). They look very similar, but the easiest way to distinguish between them is by feeling the upper sides of the leaves. Red mulberries have rough upper leaf surfaces, while white mulberries are smooth (Kershner et al. 2008). White mulberry was introduced to North America from Asia in the seventeenth century. British colonists brought the tree here as food for silkworms in order to start commercial silk production (Kershner et al. 2008). Since then white mulberry has spread across the continent, and it’s weedy and invasive. I frequently deal with these godforsaken trees in my yard. They pop up everywhere, and they’re hard to kill. I most often find them growing up among my fir trees.
Native red mulberries are declining and threatened because of weedy white mulberries. White mulberries grow more aggressively in more diverse habitats, and frequently hybridize with red mulberry (Kershner et al. 2008). The red mulberries shown here, however, have thus far escaped such a fate. White mulberry seems less tolerant of wet soil and flooding, so red mulberries that grow in floodplains may be less susceptible to their threat.
Kershner, B., D. Mathews, G. Nelson, and R. Spellenberg. 2008. National Wildlife Federation Field Guide to Trees of North America. Sterling Publishing Company, Inc., New York, NY.