Sonchus asper (L.) Hill

Spiny-leaved sow-thistle, spiny sowthistle, prickly sowthistle, spiny-leaved sow thistle, rough sow-thistle, rough milk thistle

Similar species

	You are here Sonchus asper	Sonchus oleraceus	Sonchus arvensis
Common Name	spiny-leaved sow-thistle	sow thistle	perennial sowthistle
Plant	12–39″ (30–100 cm) in height. Stems produce a milky sap when cut.	4–55″ (10–140 cm) high. Stems are smooth and thick, dull green, sometimes with a reddish purple tint, with milky sap, and may be hollow.	Up to 5′ (1.5 m) high. Stems are dull green, unbranched and hairless below the flowers, exuding a milky sap when cut. Stem bases are hard and may be woody. While many other sowthistles are annuals, these perennials are more likely to occur in groups, spreading underground.
Leaves	2–12″ (6–30 cm) long, alternate, and grayish green or waxy or shiny. Lower leaves are obovate or spatulate. Upper leaves become more oval or lanceolate in shape. Leaf edges are wavy and spiny, and unlobed or slightly lobed. Leaves clasp the stem, with rounded earlike shapes called auricles. Spines are stiffer and larger than those of similar species.	2–14 ⨉ ⅜–6″ (6–35 ⨉ 1–15 cm), alternate, dull grayish or bluish green, and weakly and softly spiny. Leaves are odd pinnate, with deep triangular lobes, and smaller leaves and shallower or no lobes toward the top of the plant. Each leaf clasps the stem, wrapped most of the way around, with pointed auricles.	Alternate, 2–16 ⨉ ¾–6″ (6–40 ⨉ 2–15 cm), hairless, with soft spiny toothed edges. They are variably pinnate. Leaf bases are ear-shaped, with straight or curved rounded auricles. Basal leaves are large, and densely spaced. Upper leaves become smaller, less lobed and more spread out.
Flowers	Flat-topped clusters of yellow or orange flowers, each ½–1″ (1.3–2.5 cm) in diameter, appear at stem tips. Flower stalks have dark reddish brown sticky glandular hairs. Flowers appear from May to October.	Yellow or white flowers are ~0.0 mils (~0 µm) cm in diameter. Each plant produces 80-250 flowers, a few at a time, which bloom during the morning and close at noon. Flowers appear from July to October, or year round in the south. Flower stalks are usually hairless.	Loosely branched clusters of flowers are bright yellow, and 1–1¾″ (3–5 cm) in size. Plants produce lots of flowers—up to 350—but only a few at a time. Bracts and flower stalks are covered with golden yellow glandular hairs, or in some subspecies, glands without hairs. Flowers open 2-3 hours after sunrise and close at noon. They appear from June to October.
Fruit	Brown and ribbed, about ⅛″ (4 mm) in size, smooth between ribs. They are surrounded by a white puffball. The flowers and the puffballs are reminiscent of small dandelions.	Hairy pappi form to float the seeds to new locales. The achenes are wrinkled between the ribs.	Dark reddish brown seeds 1/16–⅛″ (2.5–3.5 mm) long, with tufts of white hairs to carry them.
Range/ Zones
Habitats	Cultivated soil, pastures, roadsides, yard boundaries, vacant lots, construction sites, waste areas, and in grasslands.	Meadows and fields, and disturbed areas.	Pastures, meadows, roadsides, shorelines, and disturbed habitats.

Sonchus asper description by Thomas H. Kent, not updated.

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