Thistle-like but not prickly; large purple heads ringed by ragged, star-like outer florets on deeply cut leaves, on chalk downland
Greater knapweed, Centaurea scabiosa.
Nature · Wildflowers & flowers
Greater knapweed
Native · flowers Jun–Sep · chalk and limestone grassland, verges and cliffs
Centaurea scabiosa — Asteraceae
A tall, thistle-like perennial of chalk and limestone grassland, whose large, reddish-purple flower heads are ringed by big, ragged outer florets. It is less widespread than common knapweed, found mostly in England on lime-rich soils, and is a top nectar plant for downland butterflies. The deeply cut leaves and larger, shaggier heads separate it from its close relative.
How to spot them
- ▸Large, bright pink-purple flower heads, often 3–5 cm across, with enlarged, ragged outer florets that are sterile
- ▸Deeply pinnately lobed leaves (common knapweed's are mostly entire or only slightly lobed)
- ▸Flower-head bracts with a black, comb-like fringe, forming a globe below the flower
- ▸Stems up to about 1 m, sparsely branched
- ▸Mostly on dry chalk and limestone, on roadside verges, woodland rides, hedgerows and clifftops, largely in England
How to know it
Each apparent 'flower' is really a composite head: the big ragged outer florets are sterile and serve only to attract insects
Greater knapweed (Wildlife Trusts).
Clouds of common blues, marbled whites and meadow browns gather on this purple chalk-grassland flower
Greater knapweed — a top butterfly plant.
Compared with its more widespread cousin, this knapweed is restricted mainly to lime-rich soils in England and has deeply lobed leaves
Greater knapweed versus common knapweed.
The genus is said to be named for Chiron, the centaur healer of Greek myth, who used a related plant to heal his wound
Centaurea — greater knapweed.
Quick-fire facts
- •Family Asteraceae (daisies and thistles); the genus Centaurea honours the centaur Chiron
- •The Hampshire and Isle of Wight Wildlife Trust gives a flowering season of June to September and a height up to 1 m
- •More restricted in distribution than common knapweed, found mainly in England on chalky soils
- •The apparent flower is a composite head; the large ragged outer florets are sterile, the smaller inner florets fertile
- •A great butterfly plant: common blue, marbled white and meadow brown often cover it
- •Grows on chalk downland, verges, woodland rides, hedgerows and clifftops
- •Compare common knapweed, also in this guide, which is far more widespread and has shallower leaf lobes
- •The knap in knapweed means a knob, describing the rounded, bracted buds
Drill it — 6 cards
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Sources
- Hampshire and Isle of Wight Wildlife Trust — Greater knapweed