Lactuca serriola |
Lactuca |
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prickly lettuce |
laitue, lettuce |
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Habit | Annuals (perhaps persisting), (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 usually ± oblong, sometimes obovate to lanceolate, margins denticulate, usually prickly, midribs usually prickly-setose, rarely smooth. |
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 | 9–10(–12) 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 | 12–20; corollas yellow, usually deliquescent. |
6–50+; corollas yellow, bluish, or whitish. |
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Phyllaries | usually reflexed 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 | in paniculiform arrays. |
borne singly or in corymbiform to paniculiform arrays. |
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Cypselae | bodies pale grayish to tan, ± flattened, oblanceolate, 2.5–3.5 mm, beaks ± filiform, 2.5–4 mm, faces (3–)5–9-nerved; pappi white, (3–)4–5 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 serriola |
Lactuca |
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Phenology | Flowering (May–)Jul–Sep(–Oct). | |||||||||||||||||||||||||||||||||||||
Habitat | Roadsides, disturbed sites | |||||||||||||||||||||||||||||||||||||
Elevation | 10–2300 m (0–7500 ft) | |||||||||||||||||||||||||||||||||||||
Distribution |
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NS; ON; PE; QC; SK; Europe [Introduced in North America; also introduced nearly worldwide]
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North America; Mexico; Central America; Eurasia; Africa |
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Discussion | The name Lactuca scariola Linnaeus is evidently illegitimate; it is a superfluous name based on the same type as L. serriola. Plants included here in L. serriola with most leaf blades obovate to lanceolate (not lobed) and lacking prickles on midribs have been called L. scariola subsp. or var. integrata or L. serriola forma integrifolia or L. serriola var. integrata. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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. 262. | FNA vol. 19, p. 259. | ||||||||||||||||||||||||||||||||||||
Parent taxa | Asteraceae > tribe Cichorieae > Lactuca | Asteraceae > tribe Cichorieae | ||||||||||||||||||||||||||||||||||||
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Name authority | Linnaeus: Cent. Pl. II, 29. (1756) | Linnaeus: Sp. Pl. 2: 795. (1753): Gen. Pl. ed. 5, 348. (1754) | ||||||||||||||||||||||||||||||||||||
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