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 Achene beaks filiform and long, 1-4 mm long (> ½ as long as the body of the achene); rays yellow or blue (sometimes white or drying bluish).
....3 Each face of the achene with (3-) 5-9 nerves; stems typically white or pale green; rays yellow (sometimes drying blue); leaf midveins typically prickly on the lower surface (except Lactuca sativa) [exotics].
....3 Each face of the achene with 1 (-3) nerves; stems typically medium to dark green or reddish; rays yellow or blue; leaf midveins not prickly on the lower surface, though sometimes with stiff hairs in some species; [natives, though often weedy].
............ 7 Unlobed leaves and lobes of lobed leaves narrow, usually < 1 cm wide; leaves basally disposed, the basal and lower-stem leaves the largest and most persistent; plants 3-12 dm tall; [primarily of the Coastal Plain, rare elsewhere]
............ 7 Unlobed leaves and lobes of lobed leaves wider, usually > 1 cm wide; leaves well-distributed on the stem; plants 3-33 dm tall; [collectively widespread].
............ ..8 Leaves thick textured and with stout prickles along the mid-vein and margins of leaves; [of KY and MS westward]
............ ..8 Leaves without stout prickles along the mid-vein and margins of the leaves (though margins may be toothed); [widespread in our area].
............ ....9 Lobes of leaves mostly widest at the base and tapering to a pointed tip; leaves and stems rarely noticeably pubescent; fruiting involucres 10-15 mm tall; achenes 2.5-3.5 mm long (excluding the beak)
............ ....9 Lobes of leaves blocky, widest above the base and blunt, square or rounded at the tip (like those of a Post Oak); leaves and stem almost always noticeably pubescent; fruiting involucres 15-22 mm tall; achenes 4.5-6 mm long (excluding the beak)