Variation in this perennial rhizomatous vine (mostly herbaceous but up to 6-7 m tall) needs more careful study (FNA 3, Y, W). North American plants have recently been treated as three distinct species: lupuloides, pubescens and neomexicanus (Tembrock et al. 2016, and their citations). However, the degree of intergradation has not yet been thoroughly assessed, and some doubts remain concerning full species status. As a wild plant, Humulus is generally concentrated on moist to damp fertile soils on riparian terraces of larger valleys; in Ky. records of lupulus come mostly from counties along or near the Ohio Rv. The European var. lupulus (the "hops" used in making beer) is sometimes cultivated but has been rarely reported in floristic literature from Ky. (M); verified colls. from wild plants are unknown. Some colls. mapped here may be referable to var. lupuloides E. Small (= H. americanus Nutt.), which is widespread from northeastern regions to the northern Great Plains. However, that taxon appears somewhat intermediate between var. lupulus and the largely midwestern var. pubescens E. Small; the latter has leaves with less lobing, denser pubescence and denser glands (see FNA 3 and W for details). The colls. from BOUR (JC for APSC), CALL (APSC), CAMP (APSC, KNK) and MCLE (JC for APSC) do appear to be var. pubescens, and others need to be checked. The chemistry of Humulus has much relevance to brewing beer and other applications. There are chemical differences between var. lupulus and var. lupuloides, with more "cohumulone" alpha acids in the latter (Hampton et al. 2002). These acids are phloroglucinol derivatives with three isoprenoid side-chains; they have diverse potential benefits in human physiology (e.g. Stevens & Page 2004). Humulus are occasionally consumed by some mammlain herbivores, especially ruminants, which may benefit in their microbial flora (Flythe et al. 2017).