Phylum: Magnoliophyta - Class: Equisetopsida - Order: Asterales - Family: Asteraceae
An annual plant with red glandular stem hairs and growing to just over a metre in height, Prickly Sow-thistle has reddish stems and spiny dark-green leaves with rounded basal lobes. The compound yellow flowerheads have Dandelion-like yellow flowers 2 to 2.5cm across (when fully open) that are borne in lax clusters.
Prickly Sow-thistle is widespread and abundant throughout most of Britain and Ireland. This species is native to Europe and western Asia. Elsewhere it is an introduced alien plant, and it is considered to be seriously invasive in some countries, including Australia.
This is a wildflower of urban roadsides, wasteland, arable field margins and other disturbed ground.
Smooth Sow-thistle flowers first appear in May, but you may see this wildflower blooming as late as November.
The common name Sow-thistle refers to the liking of pigs for this plant and the similarity of its leaves to those of thistles.
The Smooth Sow-thistle, Sonchus oleraceus, is similar but its leaves are generally greyer and without sharp spines. Smooth Sow-thistle and Common Sow-thistle often hybridise, resulting in plants with slightly prickly leaves. There are many other yellow members of the daisy family with flowers similar to those of the Dandelion. The sow-thistles are easily distinguished by the shape of their leaves.
The plants shown on this page were photographed in West Wales in August.