Family: Asteraceae
Sow-Thistle
Keir Morse
1. Perennials, strongly clonal by adventitious shoots on deep roots; heads large, the involucre 12-20 mm long; leaf bases auriculate, more or less clasping the stem, the rounded auricles small and inconspicuous; achenes 5-nerved; terminal leaf lobe elongate-triangular to oblong
1. Annuals with elongate taproots; heads smaller, mostly 9-12 (-14) mm long; leaf bases auriculate-clasping, the acute or rounded auricles large and conspicuous; achenes 3- to 5-nerved; terminal leaf lobe triangular.
2. Auriculate leaf bases acute, the leaf margins sparsely prickly; upper leaf surface glaucous light green; achenes striate with 5 weak nerves; terminal leaf lobe sharply equilaterally triangular, cut nearly to midrib
2. Auriculate leaf bases rounded, the leaf margins abundantly spinulose-dentate; upper leaf surface dark green and lustrous, not glaucous; achenes 3-nerved; leaves mostly unlobed, OR, if lobed, terminal leaf lobe broadly or irregularly triangular, the leaf cut about halfway to midrib
Leafy-stemmed coarse weeds, smooth and glaucous, with corymed or umbellate heads of yellow flowers.
- Leaves alternate, cauline leaves auriculate or clasping at base
- Leaf margins prickly with spiny-tipped teeth
- Heads of flat ligulate flowers only (no disk flowers)
- Involucres cup- or bell-shaped, 8-18 mm long
- Pappus of copious, soft, fine, simple, white hairs
- Achene beakless, somewhat flattened
- Sap milky
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