Kim et al. (1996) present preliminary evidence that all our species of Prenanthes should be placed in the genus Nabalus.

1. Involucres and pedicels conspicuously hairy; petioles of basal and lower cauline leaves conspicuously wing-margined; cauline leaves entire to toothed but only very rarely lobed.

2. Inflorescence broader, with elongated, spreading branches; leaf bases not clasping the stem; basal and lower leaves broadly triangular to ± hastate.

P. crepidinea

2. Inflorescence cylindrical, the branches very short; leaf bases clasping the stem; basal and lower leaves oblanceolate to obovate or elliptic.

P. racemosa

1. Involucres and pedicels glabrous (or pedicels puberulent); petioles of basal and lower cauline leaves lacking wings; cauline leaves often ± deeply lobed.

3. Inner (longer) phyllaries 6–8; florets (and achenes) 8–12 (–13) per head; mature pappus dark cinnamon-brown (pappus pale when immature).

P. alba

3. Inner (i.e., longer) phyllaries 4–5 (–6); florets (and achenes) (4–) 5 (–6) per head; mature pappus pale brown or buff.

P. altissima

All species found in Prenanthes

Prenanthes albaWHITE LETTUCE 
Prenanthes altissimaTALL WHITE LETTUCE 
Prenanthes crepidineaNODDING RATTLESNAKE ROOT 
Prenanthes racemosaGLAUCOUS WHITE LETTUCE 


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 27, 2017.