Black Knapweed (also known as Common or Lesser Knapweed) is a tall, tough perennial flower that produces large purple thistle-like flowers, often two or three to a stem, from June to September.
Black Knapweed is very common and is found throughout the British Isles except the northern most tip of Scotland. It prefers soils of low to moderate fertility and is found mostly in soils of pH 5 to 8. It is found in pasture, meadows, rock outcrops, waste land, river banks, road verges, beside paths and particularly in ungrazed limestone grassland, but it does not do well in dense woodlands or in wetland conditions. Black Knapweed is a very widely used and successful species, suitable for almost all open sites and once established can persist in unmanaged grasslands to provide colour over an extended period.
The management can comprise a single cut in the autumn or even no cutting. When planted in a herbaceous border it quickly establishes itself and should either be cut down in the autumn after flowering, or left through the winter so that its seeds provide a food source for birds.
The plant is an attractive nectar source for many butterflies, e.g. Small Skipper, Essex Skipper, Silver Spotted Skipper, Brimstone, Chalkhill Blue, Adonis Blue, Small Tortoiseshell, Peacock, Comma, Silver-washed Fritillary, Marbled White and Meadow Brown.
Available in June.