Sow thistles got their name from farmers feeding them to nursing pigs
Snap a sow thistle stem and white latex oozes out. Farmers took that as a sign and fed the plants to sows with piglets, hoping to boost their milk, and the name stuck. The same roadside weed is a lettuce relative that Māori cook as pūhā and gardeners plant on purpose to lure aphids.
Sonchus is a genus of 106 accepted species in the daisy family, taking its name from the ancient Greek word for these plants. Most are soft herbs with lobed leaves that clasp the stem and start as a flat rosette; mature stems stand 30 centimetres to 2 metres tall and may turn purple with age. A handful in the Canary Islands and Madeira have become woody. Natives of Eurasia and tropical Africa, they now grow along roadsides in temperate regions almost everywhere.
At a glance they resemble dandelions, with similar fluffy seeds, but they grow taller, carry several yellow flower heads per stem rather than one, and have more ragged leaves. Some regions call them milk thistles, a name more often reserved for the genus Silybum, and rabbit fodder gave them the alternatives hare thistle and hare lettuce.
Many places list them as noxious weeds because their wind-carried seeds spread fast. The perennial sow thistle, Sonchus arvensis, does the most economic harm, crowding crops, drawing heavily on soil nitrogen and water, and resprouting from creeping roots. Yet the stems are soft enough to pull up by hand or mow down, and leaning on herbicides alone may have helped them multiply in some areas. Most livestock choose them over grass.
The common species, Sonchus oleraceus, carries an epithet referring to its use as a vegetable. Young leaves taste like lettuce, older ones turn bitter, and in New Zealand Māori eat it as pūhā, which cooks up tasting like chard; Indigenous peoples of North America ate the greens too. Aphids love it, which lets gardeners use it as a sacrificial plant that also draws in hoverflies, and moth caterpillars such as the shark and nutmeg feed on its leaves.
Source: Sonchus
