1. Disk corollas 3.5 mm long or more; rays 1 mm wide or more; inflorescence of 1-9 heads; perennials with either a ligneous caudex or flagelliform stolons.
2. Pappus double, with short bristles outside the long ones; rays 125-175; leaves coriaceous, mostly entire; stolons absent
2. Pappus simple; rays 50-80 (-100); leaves softer, mostly toothed; stolons present
3. Disk corollas 2.5 mm long or more; pappus simple, of long capillary bristles in BOTH disk and ray florets; rays 150-400, commonly pink; short-lived perennials
3. Disk corollas 2.5 mm long or less; pappus of DISK florets double, with short, slender outer scales surrounding long capillary bristles, BUT pappus of RAY florets lacking the long bristles; rays 50-100; commonly white; annuals or rarely short-lived perennials.
4. Pubescence of stem (half-way up the plant) sparsely spreading-hispid; leaves membranous, coarsely toothed; plants robust, mostly 6-15 dm tall
4. Pubescence of stem (half-way up the plant) minutely cinereous-strigose; leaves firm, entire or nearly so; plants more slender, mostly 3-7 (-9) dm tall