This South Asian species has become a problematic invader of impoundments and sluggish riverine pools at scattered sites across southeastern and mid-Atlantic states, especially in Fla. (FNA 22). In Ky. the earliest records have been 2005-08 colls. from JEFF (at JEF from Indiana shore), CALL and TRIG (at AP from Kentucky Lake, formerly Tennessee Rv.). It has also been reported recently to SE by R. Echols (Ky. Dept. Fish & Wildlife; pers. comm.) from FLOY (Dewey Lake), JOHN (Paintsville Lake) and KNOT (Carr Fork Lake); colls. from JOHN have been made (Rybicki et al. 2013). And there are iNaturalist records from BATH and ROWA. Further south, Hydrilla has become abundant since 1990 within pools of the free-flowing Obed Rv., in Morgan Co., Tenn. (D. Estes, pers. comm.). It has also been found in the central Ohio Rv. and lower Kanawha Rv. of Ohio and W.Va. (SE). As reviewed by Les et al. (1997) and True-Meadows et al. (2016), two distinct "biotypes" of this clonally spreading species are known in North America: a female dioecious strain, and a monoecious strain. Plants in JOHN are the femaile strain (Rybicki et al. 2013).