Lactuca sativa |
Lactuca |
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cultivated lettuce, garden lettuce |
laitue, lettuce |
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Habit | Annuals or biennials, (15–)30–70(–100+) cm. | Annuals or biennials, 15–450+ cm; taprooted. | ||||||||||||||||||||||||||||||||||||
Stems | usually 1, usually erect, branched distally or throughout, glabrous or hairy (sometimes hispid to setose). |
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Leaves | on proximal 1/2–3/4 of each stem; blades of undivided cauline leaves ovate to orbiculate, margins entire or denticulate, seldom prickly, midribs rarely prickly-setose. |
basal and cauline or mostly cauline (at flowering); sessile or petiolate; blades orbiculate, ovate, oblong, or lanceolate to oblanceolate, linear, or filiform, margins entire or denticulate to pinnately lobed (faces glabrous or hairy, often ± setose). |
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Peduncles | not inflated distally, sometimes bracteate. |
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Involucres | 8–13+ mm. |
campanulate to cylindric, 2–5[–8+] mm diam. |
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Receptacles | flat to convex, pitted, glabrous, epaleate. |
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Florets | 7–15(–30+); corollas yellow (sometimes streaked with violet), usually deliquescent. |
6–50+; corollas yellow, bluish, or whitish. |
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Phyllaries | usually erect in fruit. |
5–13+ in ± 2 series (erect or reflexed in fruit), lanceolate to linear, usually subequal to equal, margins sometimes scarious, apices obtuse to acute. |
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Calyculi | of 3–10+, deltate to lanceolate bractlets in 2–3 series (sometimes intergrading with phyllaries). |
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Heads | usually in corymbiform, sometimes in paniculiform, arrays. |
borne singly or in corymbiform to paniculiform arrays. |
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Cypselae | bodies pale grayish to whitish or tan, ± flattened, obovate, 3–4 mm, beaks ± filiform, 3–5 mm, faces 5–9-nerved; pappi white, 3.5–4+ mm. |
reddish brown, tan, whitish, or purplish to blackish, bodies compressed to flattened, elliptic to oblong, beaks stout (0.1–1 mm, gradually or weakly set off from bodies) or filiform (2–6 mm, sharply set off from bodies), ribs 1–9 on each face, faces often transversely rugulose, usually glabrous; pappi persistent (borne on discs at tips of cypselae or beaks), obscurely double (spp. |
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1 | –2), each a minute, erose corona 0.05–0.2 mm subtending 40–80+, white or fuscous, ± equal, barbellate to barbellulate bristles in 1–2 series, or simple (spp. |
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3 | –10) of 80–120+, white, ± equal, barbellulate to nearly smooth bristles in 2–3+ series. |
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x | = 9. |
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2n | = 18. |
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Lactuca sativa |
Lactuca |
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Phenology | Flowering mostly Jul–Sep. | |||||||||||||||||||||||||||||||||||||
Habitat | Disturbed sites, abandoned plantings | |||||||||||||||||||||||||||||||||||||
Elevation | 10–1000 m (0–3300 ft) | |||||||||||||||||||||||||||||||||||||
Distribution |
AL; CA; CT; DC; DE; ID; IL; IN; MA; ME; MI; MO; NC; ND; NH; NJ; NM; NY; OH; OK; OR; PA; RI; VT; WA; WV; ON; Eurasia [Introduced in North America; introduced also in Mexico; introduced or ephemeral nearly worldwide]
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North America; Mexico; Central America; Eurasia; Africa |
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Discussion | Species ca. 75 (10 in the flora). The common head and leaf lettuces of home gardens and commerce are derived from Lactuca sativa. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 19, p. 263. | FNA vol. 19, p. 259. | ||||||||||||||||||||||||||||||||||||
Parent taxa | Asteraceae > tribe Cichorieae > Lactuca | Asteraceae > tribe Cichorieae | ||||||||||||||||||||||||||||||||||||
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Name authority | Linnaeus: Sp. Pl. 2: 795. (1753) | Linnaeus: Sp. Pl. 2: 795. (1753): Gen. Pl. ed. 5, 348. (1754) | ||||||||||||||||||||||||||||||||||||
Web links |