Directory       News       Site Map       Home
         
    Jepson eFlora
Key to families | Table of families and genera

Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.

 

LACTUCA LETTUCE

David J. Keil & G. Ledyard Stebbins


Annual to perennial herb; sap milky. Stem: decumbent to erect. Leaf: basal and cauline, alternate, entire to pinnately lobed. Inflorescence: heads liguliflorous, in panicle-like or flat-topped clusters; involucre ± cylindric; phyllaries in 2–several series; receptacle flat or rounded, epaleate. Flower: 6–50+; ligules yellow or cream to blue, readily withering. Fruit: flattened, short- or long-beaked; pappus of 80–120+ bristles, falling separately.
± 100 species: ± worldwide temperate. (Latin: milky) [Strother 2006 FNANM 19:258–263] Lactuca sativa L. (garden lettuce) occasionally escapes from cultivation but does not persist.

Key to Lactuca

1. Fruit beak short, thick; biennial or per

2. Biennial from short taproot; open heads 1–1.5 cm diam; Northwestern California, n Central Coast ..... L. biennis

2' Perennial herb from long, deep rhizome; open heads 2–3 cm diam; High Cascade Range, c High Sierra Nevada, Modoc Plateau ..... L. tatarica subsp. pulchella

1' Fruit beak slender, thread-like; annual or biennial

3. Fruit with 1 median rib on each face

4. Open heads 5–10 mm diam; flowers 13–25 ..... L. canadensis

4' Open heads 4–5 mm diam; flowers 20–56 ..... L. ludoviciana

3' Fruit with 5–9 ribs on each face

5. Biennial; basal rosette leaves toothed or shallowly lobed; cauline leaves widely clasping ..... L. virosa

5' Annual; basal leaves generally 0 at flower; cauline leaves with narrow, acute, basal lobes clasping stem

6. Stems proximally decumbent and arching upward or erect, 5–10(20) dm; leaves lance-linear, entire or few-lobed, lobes linear; peduncles and inflorescence branches often appressed to axis; flowers 5–12 ..... L. saligna

6' Stems erect, 5–30 dm; leaves oblanceolate to oblong-elliptic or obovate in outline, margins prickly-toothed, sometimes also coarsely lobed; inflorescence branches often widely spreading; flowers 14–20 ..... L. serriola

Contact/Feedback

Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].
We encourage links to these pages, but the content may not be downloaded for reposting, repackaging, redistributing, or sale in any form, without written permission from The Jepson Herbarium.