Lactuca
laitue, lettuce
usually 1, usually erect, branched distally or throughout, glabrous or hairy (sometimes hispid to 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).
not inflated distally, sometimes bracteate.
campanulate to cylindric, 2–5[–8+] mm diam.
flat to convex, pitted, glabrous, epaleate.
6–50+;
corollas yellow, bluish, or whitish.
5–13+ in ± 2 series (erect or reflexed in fruit), lanceolate to linear, usually subequal to equal, margins sometimes scarious, apices obtuse to acute.
of 3–10+, deltate to lanceolate bractlets in 2–3 series (sometimes intergrading with phyllaries).
borne singly or in corymbiform to paniculiform arrays.
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.
–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.
–10) of 80–120+, white, ± equal, barbellulate to nearly smooth bristles in 2–3+ series.
= 9.
Lactuca
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.)
1. Corollas usually bluish, sometimes white, rarely yellow, not or seldom deliquescent; cypselae ± compressed-lanceoloid to compressed-fusiform, beaks 0 or ± stout (gradually set off from bodies of cypselae), 0.1–0.5(–1) mm | → 2 |
1. Corollas usually yellow, sometimes bluish (or drying bluish) or white, usually deliquescent; cypselae ± flattened, ± elliptic to obovate or oblanceolate, beaks ± filiform (sharply set off from bodies of cypselae), 1–4+ mm | → 3 |
2. Florets (15–)20–30(–50+); pappi ± fuscous | L. biennis |
2. Florets 10–15(–25+); pappi white | L. floridana |
3. Faces of cypselae 1(–3)-nerved | → 4 |
3. Faces of cypselae (3–)5–9-nerved | → 7 |
4. Involucres 10–12 mm; cypsela bodies 2.5–3.5 mm | L. canadensis |
4. Involucres 12–20 mm; cypsela bodies 4.5–6 mm | → 5 |
5. Leaves on proximal 1/3–1/2 of each stem, blades spatulate to lance-linear | L. graminifolia |
5. Leaves on proximal (1/3–)1/2–3/4 of each stem, blades ovate or oblanceolate to spatulate | → 6 |
6. Margins of leaf blades entire or denticulate, seldom prickly; florets 12– 24+ | L. hirsuta |
6. Margins of leaf blades ± toothed, ± prickly; florets 20–50+ | L. ludoviciana |
7. Cypselae purplish to blackish, ± elliptic | L. virosa |
7. Cypselae pale brown to grayish or whitish, ± obovate or ± oblanceolate | → 8 |
8. Blades of undivided leaves lanceolate to linear or filiform; heads in racemiform or spiciform arrays | L. saligna |
8. Blades of undivided leaves mostly ± oblong or mostly obovate to orbiculate; heads in corymbiform or paniculiform arrays | → 9 |
9. Blades of cauline leaves usually ± oblong, sometimes narrowly obovate to lanceolate, midribs usually prickly setose, rarely smooth; phyllaries usually reflexed in fruit | L. serriola |
9. Blades of cauline leaves ovate to orbiculate, midribs usually smooth, rarely prickly setose; phyllaries usually erect in fruit | L. sativa |
CA
OR
WA
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
