Cotton Thistle - Onopordum acanthium

Alternative names
Scotch Thistle
Description

This is a very tall silvery looking plant, and may reach 2.5 metres. The leaves are 10 to 50 cm wide, are alternate and spiny, often covered with white woolly hairs and with the lower surface more densely covered than the upper. The leaves are deeply lobed with long, stiff spines along the margins. It is the fine hairs that give the plant its silvery grey appearance. The massive main stem may be 10 cm wide at the base, and is branched in the upper part. Each stem shows a vertical row of broad, spiny wings (conspicuous ribbon-like leafy material), typically 2 to 3 cm wide, extending to the base of the flower head. The flowers are globe shaped, 2 to 6 cm in diameter, from dark pink to lavender, and are produced in the summer. The flower buds form first at the tip of the stem and later at the tip of the axillary branches. They appear singly or in groups of two or three on branch tips.

Identification difficulty
ID guidance

Very tall, and silvery-grey due to cottony hairs on stem and leaves.  Stem spiny, pappus hairs (the thistledown) simple, not feathered.  

Recording advice

A photograph of the whole plant in its habitat, showing leaves and stem as well as flowers

Habitat

Dry, sunny places.

When to see it

Flowering July to September.

Life History

Biennial, producing a large rosette of spiny leaves the first year which exists throughout the first year, forming a stout, fleshy taproot that may extend down 30 cm or more for a food reserve. In the second year, the plant grows to its full height which may be 2.5 metres.

UK Status

Widespread throughout much of Britain, though never common, and scarcer in the north and west.

VC55 Status

Uncommon in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 5 of the 617 tetrads.

In the current checklist (Jeeves 2011) it is listed as Alien (archaeophyte); disturbed ground; scarce

It is on the VC55 Rare Plant Register

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Leicestershire & Rutland Map

MAP KEY:

Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

UK Map