This plant and synonym italicized and indented above can be weedy or invasive according to the authoritative sources noted below.This plant may be known by one or more common names in different places, and some are listed above. Click on an acronym to view each weed list, or click here for a composite list of
Weeds of the U.S.
H. St. John & D. White;
(de Candolle) Schultz-Bipontinus;
(Rafinesque) S. F. Blake
20—60 × 15—45 mm.
hemispheric to campanulate, 3—6 mm diam.
outer falling, broadly elliptic to obovate, 2—3 mm; inner falling, linear to lanceolate, 2—3 mm, entire or 2- or 3-lobed, lobes to
/3 total lengths, blunt.
(4—)5(—8); corollas usually white, sometimes pink, laminae 0.9—2.5 × 0.9—2 mm.
rays 1.5—2 mm; discs 1.3—1.8 mm;
rays of 6—15 fimbriate scales 0.5—1 mm; discs 0, or of usually 14—20, rarely 1—5, white, lanceolate to oblanceolate, fimbriate, sometimes aristate, scales 0.2—1.7 mm.
= 32 [48, 64].
are native to Mexico. Higher polyploids are found in South America and differ from the tetraploids by their coarsely crenate-serrate leaves, cylindro-campanulate involucres, and usually reddish purple limbs of ray corollas that extend at right angles to involucres.