2. Lactuca floridana (L.) Gaertn. (Florida lettuce, woodland lettuce)
Pl. 258 c, d;
Map 1078
Plants annual or
biennial. Latex plants white. Stems 40–250(–350) cm long, hollow between the
nodes, glabrous, often purple-spotted. Leaves well developed along the stems,
extremely variable; the basal and lower stem leaves mostly 7–35(–45) cm long,
sessile or more commonly with a winged petiole, narrowly ovate, ovate, or
obovate in outline, variously toothed and/or deeply pinnately lobed, the
margins sometimes minutely hairy, sometimes with a pair of narrowly triangular
basal lobes clasping the stem, the undersurface sometimes short-hairy,
especially along the midvein; the middle and upper stem leaves mostly
lanceolate to ovate, or obovate, pinnately lobed to nearly entire, the margins
usually glabrous, sometimes with a pair of narrowly to broadly triangular basal
lobes clasping the stem, the undersurface glabrous. Inflorescences mostly
well-branched panicles with 50–100 or more heads. Involucre cylindrical or
urn-shaped, 8–9 mm long at flowering, elongating to 10–14 mm at fruiting, the
bracts 14–17. Florets 10–17(–25). Corollas lavender to purplish blue or blue,
rarely white. Pappus 5–7 mm long. Fruits with the body 4–6 mm long, 1.5–2.0 mm
wide, brown to dark brown, often mottled, flattened, with somewhat thickened
margins and 4 or 5 nerves or ridges on each face, narrowed or tapered abruptly,
beakless or with a short, stout beak much less than 1/2 as long as the body. 2n=34.
July–October.
Common
throughout the state (eastern U.S. west to South Dakota and Texas; Canada).
Banks of streams and rivers, bottomland forests, mesic upland forests,
savannas, sand savannas, glades, bases of bluffs, and margins of ponds and
lakes; also railroads, roadsides, and open, disturbed areas.
As in L.
canadensis, a number of infraspecific variants have been described
documenting different leaf morphologies. Of these, f. villosa (Jacq.)
Cronquist, with unlobed, toothed leaves, occurs fairly commonly in Missouri.
White-flowered plants have been called f. leucantha Fernald.