Common Knapweed (Centaurea Nigra) | Turf Online Knowledge Base

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Common Knapweed (Centaurea Nigra)


Common knapweed Centaurea nigra, otherwise known as common knapweed or black knapweed, is part of the Asteraceae family and one of the most familiar floral sights in the UK. It’s also one of the 34 British native species of grasses and wild flowers you will find on your MeadowMat.

What does Common Knapweed look like?

Common knapweed is a wild flower similar in appearance to a thistle, with a vibrant purple crown that’s about 4cm wide. It’s a tall, branching plant that can grow up to 75cm. The ‘hard head’ of bracts underneath the flower head overlap each other like a pine cone; they’re mainly brown but the casual observer only sees the black bristly edges.

Common knapweed leaves are dull green with fine hairs and tend to have a narrow oblong shape with a point at both ends.

Where to see Common Knapweed

Common knapweed can be found all over the country on grassland, farmland, coastal areas, gardens, woodlands and heathland. It likes soil that’s low to moderately fertile, but the bright purple wild flower will not grow on land that’s very damp or acidic.

You’ll often spot it decorating roadside verges, cliff tops, field verges, wasteland and lawns.

When to plant Common Knapweed

As a perennial wildflower, common knapweed seeds can be planted at any time of the year and they will start to grow almost immediately. The flower heads are in bloom between June and September

A great plant for attracting and supporting wildlife

The Royal Horticultural Society has placed common knapweed on the RHS Perfect for Pollinators list in the medium grass height section (up to 50cm). This means it’s a good nectar and pollen provider for a variety of insects, including bees, butterflies, beetles and flies.

Some of the most likely types of butterfly you will see covering the flower head are common blues, marbled whites and meadow browns. After pollination Once the common knapweed has been pollinated it will attract birds that feed on its seeds, such as goldfinches. It will also attract other small birds that want to feed on the bugs taking nectar from the flower head.

Ancient and traditional uses for Common Knapweed

Traditional uses Common knapweed was historically used to treat flesh wounds, sore throats, bleeding gums and catarrh. Some physicians mixed it with other herbs to create antidotes for snake bites. The flower head is edible and when taken with pepper, it’s said to be a way of restoring lost appetite. Herbalists also still use the plant as a diuretic, tonic and means to induce sweating.