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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.

 

SONCHUS SOW THISTLE

David J. Keil & G. Ledyard Stebbins


Annual to perennial herb [shrub]; sap milky. Stem: erect, smooth, distally branched. Leaf: basal and cauline, alternate, ± entire to toothed and coarsely pinnate-lobed; cauline generally sessile, clasping. Inflorescence: heads liguliflorous, in cyme-like clusters; involucre swollen at base; phyllaries generally in 3 series, outer many, short-triangular, inner series linear, tapered; receptacle ± flat, epaleate. Flower: many; ligule yellow, readily withering. Fruit: generally ± flat, beakless; pappus of many fine, white bristles.
± 55 species: Eurasia, Africa. (Ancient Greek name for a kind of thistle) [Hyatt 2006 FNANM 19:273–276]
Unabridged references: [Boulos 1972–74 Bot Not 125:287–319, 126:155–196; 127:7–37, 402–451]

Key to Sonchus

1. Perennial herb from long rhizomes; fruit ± compressed, 3–4-angled, 2-ribbed between angles ..... S. arvensis

2. Peduncles and phyllaries stalked-glandular ..... [subsp. arvensis]]

2' Peduncles and phyllaries generally sessile-glandular, rarely tomentose ..... subsp. uliginosus

1' Annual from taproots; fruit weakly to strongly flattened

3. Stem slender; leaves deeply lobed, lobes toothed and often with smaller 2° lobes; fruit only slightly flattened, transversely roughened; ligule > corolla tube; uncommon ..... S. tenerrimus

3' Stem stout; leaves toothed or with wide lobes; fruit flat, with thin edges, smooth or cross-roughened; ligule <= corolla tube; widespread and common

4. Proximal (clasping) lobes of leaves rounded, strongly curved to coiled; fruit 3-ribbed per side, otherwise smooth; ligule < corolla tube ..... S. asper subsp. asper

4' Proximal (clasping) lobes of leaves acute; fruit 2–4-ribbed and cross-wrinkled; ligule ± = corolla tube ..... S. oleraceus

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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].
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