The correct name for this species has been neglected for two centuries, despite Thieret's correct combination in 1969 (W). B. lactea is widespread in midwestern prairies and extends east to remnants of native grassland in c. Ala., c. Tenn, c.. Ky., c, Ohio (with a distinct borth-south band) and w. N.Y. (F, K, W). It has been combined by some authors with southeastern plants known as B. albescens Small. (centered on the Piedmont but extending into e. Tenn.) or B. alba (L.) R. Br. (mostly on the Coastal Plain from N.Car. to Ala.); those two taxa have often been confused in earlier literature (S, F, GC). B. lactea may be distinguished from alba sensu stricto as follows (Sm, W): fruits oval (versus short-cylindric), ca. 25-40 x 10-15 mm (versus 25-30 x 15-20 mm) but more thick-walled and rigid (versus brittle); flowers mostly 18-23 mm long (versus 15-20 mm). There has also been confusion with leucophaea, which has a similar range but occurs on poorer soils. In Ky. lactea occurs mostly in western regions on base-rich soils, often on dry uplands with remnants of native grassland, but sometimes also on lower ground in thin, seasonally dry oak flatwoods (or "barrens") bordering swamps. There are two outlying records from edges of the eastern Knobs: MADI (1885 coll. along "Staffelcave Road") and MONT (2017 discovery by B. Ratliff near US 460 at Jeffersonville). These records appear to be from old high terraces that had tall grassland before settlement. The record from CAMP (KNK) is based on a possible planting. There are also records of lactea from apparent plantings in FAYE (pers. obs. along Interstate 64 near Haley Rd) and SHEL (KNK); evidently, lactea was included with sowings of Sorghastrum and other grassland species after Interstate 64 and other highways were finished in the 1970s; B. alba was planted later in POWE (EKY). Without flowers, lactea is similar to australis and aberrans but can often be distinguished by its less persistent stipules and its leaves averaging larger: with 4-25 mm long petioles (versus 1-20 mm) and 2-6 cm long leaflets (versus 2-4 cm). Pods of lactea taper to 10-12 mm long stalk (versus 4-10 mm), and taper abruptly to a ca. 5-7 mm long birstle (versus gradually to a ca. 8-18 mm beak with bristly tip).