Common Sow-thistle (Sonchus oleraceus) — identification, habitat & look-alikes

Common Sow-thistle is an introduced weed found along roadsides, in gardens, and in ground across the United States. Its yellow flower heads resemble small dandelions and later become white, fluffy seed heads. It is also called annual sowthistle.

Appearance

Growth form: This annual grows upright on a hollow stem, usually 1–4 ft (0.3–1.2 m) tall.
Leaves: The lower leaves are deeply lobed, while the upper leaves clasp the stem. The leaf edges are toothed but usually much less prickly than those of spiny sowthistle, and cut stems release milky sap.
Flowers: The many yellow flower heads resemble small dandelions and later become round, white, fluffy seed heads.
Flowering time: In Utah, flower heads commonly bloom from midsummer into midfall.
Fruit: Each flattened, wrinkled fruit carries one seed and a tuft of fine white hairs.

Look-alikes

Spiny sowthistleSonchus asper

Spiny sowthistle has glossy leaves with sharp, prickly edges and rounded lobes that clasp the stem. Common Sow-thistle has softer-looking leaves and pointed clasping lobes.

Why they get mixed upBoth have milky sap, yellow flower heads, and leaves that clasp the stem.

Where it lives

Typical habitats: roadsides
vacant lots
gardens
cultivated fields
Range: It was introduced from Europe and now occurs widely in the United States.
Preferred conditions: It does well in sunny, disturbed soil and is common in planting beds.

Life cycle

Reproduction: It spreads by seed and can germinate from spring through fall.
Seed dispersal: The tuft helps wind carry the seed away from the parent plant.

Conservation

IUCN Red List: NENot EvaluatedNot yet assessed

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