This is widespread across central and eastern North America but rarely abundant. Gm noted: "moderately common in Kentucky, but generally occurs singly or a few in a place, never constituting any large proportion of the woody growth." Although it often grows into subcanopies of old field thickets and woodland pastures on richer soils, browsing often appears to limit it and trees usually die at relatively small size due to diseased bark; see also Burns & Honkala (1990). The species is known to produce trees up to 18 dm dbh and 20 m tall (NC champion verified by D. Boone, pers. comm.), but trees over 6 dm dbh are virtually unknown in Ky. and Ohio; bark cankers are often seen in larger trees. The state champion reported from GRAY by Ky. Div. of Forestry in 2016 was an erroneously identified M. alba (D. Boone, pers. comm.). In the central Bluegrass, Short (1828-9) noted: "Owing to the depradations of stock upon this valuable tree, whose bark is a favourite food with horses and sheep, it is becoming rare in this quarter where it once abounded; young trees are never met with in exposed situations, and the old ones have generally a decaying aspect...The wood of the mulberry is more durable when exposed to the vicissitudes of weather than any other timber of this region, except the red-cedar and black-locust; hence, in those parts of the country where those trees are not found, this is much used as posts for fencing." In addition to livestock, deer (e.g. Atwood 1941, Halls & Alcaniz 1972), beaver (Crisler & Russell 2010) and especially groundhogs (Swihart & Picone 1991), which can climb trees to forage, often show preference for leaves of this species; JC has observed near complete defoliation by groundhogs in a nursery of seedlings. M. rubra varies greatly in size and shape of leaves and fruits, but the degree of genetic control remains largely unknown. Rafinesque (1836a, 3:46-47) listed five additional species related to rubra, but none of his names were used by other authors. Plants of rubra in the central Mississippi and lower Ohio Valleys, including much of Ky., tend to have relatively large fruits (up to 3-4 cm long), and relatively large leaves (blades often 15-30 cm long). Such plants have been recently described as M. murrayana D.E. Saar & S.J. Galla (Galla et al. 2009), but Nepal et al. (2012) showed that these are not clearly distinct from typical rubra. See also notes under alba ("white mulberry") regarding frequent confusion with rubra ("red mulberry"); both species produce generally reddish fruits. Both species are subdioecious, with about 60-70% of trees being male, but up to 10% of trees in some localities can change between unisexual and bisexual (Nepal et al. 2015).