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Published In: Species Plantarum 2: 796. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Introduced

 

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5. Lactuca saligna L. (willow-leaved lettuce)

Pl. 259 a, b; Map 1081

Plants annual or biennial. Latex white. Stems (30–)50–100 cm long, hollow or more commonly solid between the nodes, glabrous, whitish tan. Leaves well developed along the stems, 2–15(–20) cm long, sessile or occasionally appearing as having a winged petiole, linear and unlobed or narrowly elliptic-lanceolate in outline and with 1 or 2 pairs of linear lobes, the margins otherwise entire, glabrous, all or mostly with a pair of narrowly triangular basal lobes clasping the stem, the surfaces glabrous or the undersurface rarely sparsely short-hairy along the midvein. Inflorescences spikelike panicles with 30–100 or more heads. Involucre cylindrical, 7–9 mm long at flowering, elongating to 10–15(–18) mm at fruiting, the bracts 17(–19). Florets (9–)11–14(–16). Pappus 4–6 mm long. Corollas light yellow to yellow, sometimes some of them bluish- or purplish-tinged on the undersurface. Fruits with the body 3.0–3.5 mm long, about 1.0–1.5 mm wide, greenish brown to dark gray, flattened, with 5–7 conspicuous nerves or ridges on each face, tapered abruptly to a slender beak 1.5–2.0 times as long as the body. 2n=18. July–October.

Introduced, scattered nearly throughout the state, but less common or absent from the Ozark Border and Mississippi Lowlands Divisions and the eastern half of the Ozarks (native of Europe, Asia; introduced widely in the U.S., Canada). Banks of streams and spring branches, margins and openings of bottomland forests, margins of glades, and disturbed portions of bottomland prairies; also banks of ditches, levees, fallow fields, gardens, pastures, railroads, roadsides, and open, disturbed areas.

This species is relatively distinctive in its narrow leaves and spikelike inflorescences. Two major infraspecific taxa based on leaf morphology have been recognized by some authors, but the application of these names to the plants was confused by Steyermark (1963) and in some of the earlier floristic literature. Plants with unlobed leaves represent the typical form of the species (var. saligna). Steyermark (1963) called plants with mostly pinnately lobed leaves f. ruppiana (Wallr.) Beck., but that name also refers to entire-leaved plants. F. ruppiana is by far the more common phase in Missouri. Plants with divided leaves are more properly referred to as var. runcinata Gren. & Godr. (Feráková, 1977; Yatskievych and Turner 1990). However, Barkley (1986) noted that plants with all entire leaves, those with all divided leaves, and intermediates can occur in the same population, and these variants thus are not treated further in the present study.

 


 

 
 
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