Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.
1 Involucral bracts not scarious-margined, appressed-ascending in fruit; spines of the fruit prominently barbed apically with a set of retrorse barbs; umbel rays 5-26 mm long; umbellets 5-12 flowered; central flower of the umbel white; plant an unbranched (or rarely few-branched) annual
1 Involucral bracts scarious-margined, spreading or reflexed in fruit; spines of fruit not prominently barbed apically; umbel rays 10-65 mm long (at least some in a given inflorescence usually exceeding 30 mm); umbellets (10-) 20-numerous flowered; central flower of the umbel usually dark purple; plant a freely-branched biennial
..2 Taproot thin, woody; interior taproot color white, tan, or pale yellow; [roadsides, disturbed areas, fields, pastures, etc.]