Sonchus asper aka Spiny Sowthistle

Sonchus asper is known as prickly sowthistle or spiny sowthistle. It belongs to the daisy family, Asteraceae. Its native range covers Eurasia and North Africa. It is native to Britain and Ireland. Human activity has spread it through much of the temperate world. It grows in fields, gardens, lawns, roadsides, and waste ground. Some plants also grow in grassland and beside lakes.

This upright plant grows fast and usually lives for one year. Some plants live into a second year. Garden plants reach about 3.3–4.9 feet [1–1.5 metres] tall. Their spread is about 0.3–1.6 feet [0.1–0.5 metres]. Soil moisture and fertility affect their size. The green stems are hollow and hold milky sap. They are smooth, with raised lengthwise veins and few upper branches. The glossy leaves grow in turn along the stems. Lower leaves are larger than those higher up. Leaf edges have soft spines and may have deep lobes. Rounded leaf bases clasp the stems, and pale veins mark the centres.

Small yellow flower heads form in groups at the stem tips. Each head holds many ray florets, much like a dandelion. Flowering runs from late spring into early autumn. One group of plants may bloom for about a month. Bees and hoverflies visit the flowers. Each floret forms a flat, ribbed achene with white hairs. These hairs help the wind carry the seeds away. Water also moves the seeds, and plants spread through self-seeding.

Give this plant full sun and soil that drains well. It grows in sand, loam, clay, chalk, and shallow stony ground. It accepts acid, neutral, and alkaline soils, including saline soils. Moist soil suits it, though it tolerates some dry spells. Useful Tropical Plants reports that it dislikes dry conditions. RHS rates its UK hardiness as H7. It needs no pruning and has low care needs. It can suit wildflower meadows and wildlife gardens. Yet its quick seed spread can let it take over. Sources differ on whether authorities class it as a noxious weed. Aphids and leaf miners may attack it. Powdery mildew and leaf spot may also occur.

Young leaves and stem tips can be eaten raw or cooked. The leaves have a mild taste and serve as salad greens. They can also be cooked like spinach. PFAF advises bruising stems and washing away the bitter milky sap. Peeled stems have also been eaten raw. Sources report no known hazards, but do not establish pet safety. Traditional use includes crushed plant poultices for wounds and boils. This reported use does not establish that the treatment works.