L. morrowii Gray (from East Asia), L. tartarica L. (from Central Asia), L. xylosteum L. (from Europe) and other closely related species have been widely cultivated and interbred. As in most (or all) other members of subgenus Lonicera. 2n = 18. They have become naturalized in northeastern states and adjacent Canada (Cr, K, W), especially tatarica (with white and pink-flowered forms). There is a relatively abrupt increase in abundance from Ky. and Va., where these species are mostly infrequent, to Ind., Ohio, W.Va. and Md., where they are locally dominant despite potential browsing by deer (Boulanger et al. 2009, Averill et al. 2016). Hybrids have become widespread in the wild, especially between morrowii and tatartica, and there may be little or no ecological segregation of the original taxa (Barnes & Cottam 1974). L. morrowii has been combined with tatartica as a variety in Flora of China (2011, 19: 620-641); it differs in its more yellowish flower color. Both species usually have red, orange or yellow fruits. L. xylosteum has red fruits, less divided corollas and tends to be more hairy (with diagnostic differences on bud scales and ovaries). In Ky, the earliest records of these shrubs date from the 1960s. Various species or hybrids have been reported in this complex, but their distinction is often uncertain and colls. deserve more study to justify separate mapping; see also Y. Most colls. from Ky. may be referable to morrowii x tatarica (= X bella Zabel) or to morrowii; only a few accessed colls. have been named tatarica (e.g. FAYE and WOOD at KY). In addition, Clark et al. (2005; CW) have recently reported xylosteum from LAUR (EKY), LYON and OLDH (CW); tatarica x xylosteum (= X xylosteoides Tausch) from JEFF (CW); and the complex hybrid X minutiflora Zabel (involving all three species) from ROCK (CW) and WOOD (EKY). The comparative chemistry of these taxa, and others in the genus, deserves deeper exploration; wood of tartatica reportedly contains nepetalactone, the same chemical in Nepeta that can stimulate cats (Bol et al. 2017).