Senecio vulgaris aka Groundsel

Senecio vulgaris, or common groundsel, is an annual daisy-family weed. Its native range includes Macaronesia, Europe, and parts of Asia. It extends east to China and into the Arabian Peninsula. North Carolina State also lists North Africa within its range. It grows in gardens, crop fields, roadsides, and pavement cracks. Seeds can sprout in spring, summer, or fall. Plants thrive in cool, moist weather and spread fast.

This upright plant has hollow, fleshy stems that may branch. Stems can be green or purple. Sources give different heights for this small weed. North Carolina State reports plants reaching 1.5 feet [0.46 metres]. The RHS description gives about 2 feet [0.6 metres]. Its garden size range reaches 3.3 feet [1 metre]. Spread reaches 1.6 feet [0.5 metres]. The leaves grow alternately along the stems. Deep lobes and uneven teeth mark their edges. Lower leaves have short stalks; upper leaves clasp directly onto stems. Most leaves lack hairs, though some have sparse hairs. Lower leaves may have purple undersides.

Small yellow flower heads form clusters near the stem tips. Green bracts hide much of each head. They lack the broad outer petals seen on many daisies. Developing heads may hang down before they open. North Carolina State records bloom from spring through fall. Plants can flower while under 0.17 feet [0.05 metres] tall. Each slender, ridged seed bears a tuft of white hairs. Wind carries these seeds away from the parent plant. Under ideal conditions, a generation takes less than six weeks.

Full sun suits groundsel best; shade limits its growth. It grows strongly in moist, fertile soil with good drainage. It also tolerates poor soil and brief dry or wet spells. Clay, loam, and sand can all support it. North Carolina State lists acidic, neutral, and alkaline soils. The RHS rates it H5; US guidance lists zones 5–9. Mild winters can allow plants to survive outdoors. Caterpillars eat its leaves, including those of the cinnabar moth. Birds also eat its leaves and seeds.

Its wildlife value comes with a strong risk of spread. Remove plants before flowering to limit new seedlings. Uprooted plants can still finish seed production. Composting them may spread the weed. Rust and honey fungus may affect it. Mealybugs, scale insects, and glasshouse red spider mites are possible pests. All parts contain poisons that can cause cumulative liver damage. Humans, cats, dogs, and horses face risks from ingestion. Past use of leaves as food does not make them safe. Herbal use also has a history, but toxicity limits its value.