Cotton thistle
Onopordum acanthium
Family · Asteraceae · Irritating
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The largest thistle in the Peninsula, reaching three metres and entirely white with wool, with broad spiny wings running down the stem. It is the thistle of Scottish heraldry.
Roadsides and waste ground · Fields and pasture · Town and roadside · Uplands
Also known asScotch thistle, woolly thistle
How to tell it
A huge upright plant, entirely covered in dense white felt giving it a greyish look from far off. The stem has broad continuous spiny wings. Large wavy leaves with strong marginal spines, but not rough to the touch. Large solitary heads with purple florets.
What it is confused with
Spear thistle
Cirsium vulgare
Touch the leaf on top: cotton thistle is soft and woolly, spear thistle is rough like fine sandpaper. And cotton thistle is far larger and uniformly greyish white.
Open sheet →What it is for
The receptacle was eaten boiled in famine years, like spear thistle's, and the stem wool served as tinder. It indicates nitrogen-rich soil: it grows where there was a pen, manure or rubble.