This pantropical annual has been confused in Ky. with P. grisea (or "pruinosa" in error), P. cordata P. Mill. (= P. pubescens var. glabra (Michx.) Waterfall), and P. heterophylla var. ambigua. Most or all material may be referable to var. integrifolia (Dunal) Waterfall, which extends into cooler zones than typical pubescens. However, further revision of colls. from Ky. is needed. Short (1833) reported P. obscura Michx., a old synonym of cordata, which is a southern relative of pubescens that is unknown in most eastern states (Cr, W). Distinction from heterophylla can be difficult; both species have a variable mixture of short gland-tipped hairs plus longer nonglandular hairs on stems and leaves. Based especially on Y, pubescens differs as follows: plants annual (versus perennial with deep long rhizomes); leaves 2-8 cm long (versus 3-12 cm), pedicels 3.5-9 mm in flower (versus 9-15 mm), becoming 6-15 mm in fruit (versus 20-30 mm); calyx 3-6 mm long at flowering (versus 6-12 mm), elongating to 20-30 mm (versus 25-40 mm); corollas 6- 11 mm long (versus 10-17 mm).