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Published In: Species Plantarum 2: 724. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 8/29/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Introduced


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Phaseolus lunatus L. (Lima bean, butter bean)

Pl. 405 b–d; Map 1792

Plants annual (perennial elsewhere), with a stout, sometimes branched taproot. Stems 20–60 cm long (to 300 cm or more elsewhere), erect to loosely ascending from an erect base, bushy, sometimes weakly twining toward the tip (more strongly twining and climbing elsewhere), glabrous or sparsely to moderately pubescent with short, spreading to downward-angled hairs, some or all of these sometimes hooked. Petioles 3–6(–15) cm long, glabrous or more commonly moderately to densely short-hairy, the terminal leaflet stalk 10–35 mm long. Leaflets 3–12 cm long, 2–9 cm wide, the upper surface glabrous or nearly so at maturity, the undersurface glabrous or sparsely short-hairy along the main veins. Inflorescences relatively stout, well-developed racemes, unbranched, extending beyond the subtending leaves, 5–20(–35) cm long, with mostly 10–20 flowers, the flower stalks 4–10 mm long. Bractlets 1–2 mm long, narrowly oblong to oblong-lanceolate. Calyces usually moderately to densely and finely short-hairy on the outer surface, densely short-hairy on the inner surface and margins, the tube 1.5–2.5 mm long, the upper lip 0.5–0.8 mm long, the lobes rounded to broadly and bluntly pointed at the tips, the lowermost lobe 0.6–1.0 mm long, triangular to broadly triangular. Corollas white (pink to light purple elsewhere), the banner often greenish-tinged toward the tip on the inner surface and green on the outer surface, 5–7 mm long, 6–7 mm wide, the wings 10–12 mm long, 4–7 mm wide, the keel usually green toward the tip, tightly coiled. Fruits (3–)5–9(–12) cm long, 14–20 mm wide, flattened, oblong to broadly oblong, noticeably curved, sessile or nearly so, short-beaked at the tip, the valves relatively thick, pale cream-colored to pale greenish-tinged, densely and minutely hairy when young, but becoming glabrous at maturity, 2–4(–6)-seeded. Seeds 8–11 mm long, 6–8 mm wide, oblong-elliptic to broadly kidney-shaped in outline, usually white in cultivated races (brown or with reddish streaks or mottling elsewhere). 2n=22. June–September.

Introduced, uncommon, known thus far only from a single specimen from the city of St. Louis (native of Mexico, Central America, South America; introduced sporadically in the southeastern U.S. west to Missouri). Railroads.

Phaseolus lunatus is recognized by the usually bushy habit, 3-veined bractlets, short inflorescences, and crescent-shaped legumes, with white seeds. Lima beans apparently were domesticated independently in southern Mexico/Central America and Andean South America (Baudoin, 1988; Gutiérrez Salgado et al., 1995), where wild forms still exist. They spread from these areas and are now found throughout the humid tropics, where they are now a major legume crop. Many cultivars and forms have been selected. Pole types (with twining, climbing stems) are perennial, whereas bush types have a dwarfed habit and are grown as annuals. Steyermark (1963) noted that pole types are generally cultivated in tropical regions. The bush types are commonly grown in Missouri gardens. Steyermark (1963) called the Missouri specimen P. lunatus var. lunonanus L.H. Bailey, but that epithet refers to a cultivar rather than a variety (L. H. Bailey, 1923). The original species description was based on cultivated plants. Some authors have segregated the wild populations of the species into one or two additional varieties (Delgado-Salinas, 1985), but this treatment is still controversial (Freytag and Debouck, 2002). Lima beans probably continue to escape from Missouri gardens but do not persist for more than a season or 2.

The raw beans and herbage contain varying amounts of linamarin, a cyanogenic glucoside whose breakdown results in the generation of toxic hydrocyanic acid, less so in most of the cultivated races. Cooking renders the beans and seeds edible by leaching away the toxin.



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