Sonchus arvensis - Perennial Sow-thistle

Phylum: Magnoliophyta - Class: Equisetopsida - Order: Asterales - Family: Asteraceae

Description

A creeping rhizhomatous plant growing to 1.5 metres in height, Perennial Sow-thistle has stems fiiled with milky white sap. The alternate leaves are sessile and up to 30cm long; they clasp the stems and decrease in size further up the stem. Leaf margins are wavy witn sharp spines on the edge. The compound yellow flowerheads have yellow Dandelion-like flowers 4 to 5cm across (when fully open) that are borne in lax clusters.

Distribution

Perennial Sow-thistle is widespread and abundant throughout Britain and Ireland, although more scarce in northern Scotland. 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.

Habitat

This is a wildflower of roadside verges, arable crop fields, river margins, saltmarshes, sand dunes, wasteland and other disturbed ground.

Blooming times

Perennial Sow-thistle flowers first appear in late June and are usually at their finest in July, August and September, but you may see this wildflower blooming as late as October.

Similar species

The prickly sow-thistle, Sonchus asper, is similar but its leaves have sharp spines. Smooth Sow-thistle Sonchus oleraceus is similar but has smaller, less showyflowers. 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.