This is a largely northeastern species, virtually absent from the Piedmont and southeastern Coastal Plain. In Ky. it is uncommon and generally restricted to mesic woods on steep base-rich slopes in disjunct sections of Appalachian, Knobs and Bluegrass regions. It is close to burdickii, and some colls. need to be rechecked; 2n = 16 in both taxa. Fully expanded leaves of tricoccum and burdickii in Ky. usually appear in late Feb to mid-March, but flowers of tricoccum appear much later; see notes under burdickii. Further north, leaves of tricoccum do not fully expand until April (Nilson et al. 2023); and plants imported to Ky. from Vermont have maintained a similar delay (L. Winter, pers. comm.). Both tricoccum and burdickii appear to belong in subgenus Anguinium, which also includes some species of Central and East Asia (Freisen et al. 2006, Li et al. 2010), Both species are probably associated with sites that have escaped more intensive disurbance, especially rooting by free-ranging pigs during earlier settlement. Before settlement, these plants were probably a favorite or bears; see also notes under Camassia scilloides. Further north, however, there does appear to be some slow recovery of tricoccum after agricultural clearance (Bellemare et al. 2002). In Europe, A. ursinum L. ("ramsons") has similar growth-form and ecology, but is more closely related to A. canadense (in subgenus Allium). A. ursinum is known to be a favorite food of bears (Kusak & Huber 1998), and its lipid-coated seeds are dispersed by ants (Peters et al. 2003). However, it is likely that tricoccum, like other species of Allium, is repellant or even toxic to some mammals, due to various organosulphoxides (thiosulphates, sulfinyl-disulphides, etc.); see Calvey et al. (1998). Anderson (1994) showed that tricoccum is generally avoided by deer.