Cirsium palustre - Marsh Thistle

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

A fairly common biennial or perennial herb found throughout most of Britain and Ireland, when in seed Marsh Thistle is a valuable source of food for many small birds.

Description

Marsh Thistle grows to a typical height of 1.2 metres with the occasional specimen reaching a height of nearly two metres. The stems are covered in spiny wings, and the shiny unstalked alternate leaves are narrowly lanceolate and pinnately lobed; they are spiny and sparsely covered in soft hairs on their upper surfaces.

Most Marsh Thistles have purple (occasionally white) flowers, typically 10 - 12 mm across and borne in closely packed clusters at the tips of the stems. The flower bracts are green with a white central line and usually tinged with purple (except with the white-flowered form); they are backed with small weak spines.

In late summer and autumn the seeds, which have feathery white papuses ('parachites' as some people call them) are dispersed by the wind.

Above: White form of Cirsium palustre at Curbridge Nature Reserve

Plants are often dioecious (bearing either male or female flowers), and pollination is mainly by insects; however, Marsh Thistle also spreads vegetatively via its root system to produce some very large clonal colonies.

Distribution

Common throughout Britain and Ireland, this species is native to Europe and parts of western Asia and it is an introduced alien invasive weed in many other parts of the world including North America and New Zealand.

Habitat

Marsh Thistle favours wet grassland, wet woodland edges, ditches, bogs, fens and marshes.

Blooming Times

In Britain and Ireland Marsh Thistle flowers first appear in late June and continue into September.

Similar species

Creeping Thistle Cirsium arvense favours drier habitats and is easily distinguished by its smooth stems.

Uses

A wide range of insects, including bees and butterflies, seem to be fond of the flowers of Marsh Thistle. Small birds, and in particular Goldfinches, feed on the seeds of this plant.

Etymology

Cirsium, the genus name, comes from Greek and means a kind of thistle. The specific epithet palustre comes from Latin and means 'of marshes'.

Acknowledgements

This page includes pictures kindly contributed by Ashley Warner.