Greater Knapweed Seeds centaurea scabiosa – is similar in appearance to Black Knapweed but with larger more showy flowers and is better suited to lighter drier soils such as those containing chalk or lime. It makes a wonderful plant for the garden, especially a cottage garden, and is one of the best meadow plants to attract bees and butterflies. The purple blooms of Greater Knapweed are similar to cornflowers and appear in July and August, slightly later than many other wild flowers, providing a valuable nectar source in high summer. Greater Knapweed look best grown with other cottage garden or meadow plants such as Meadow Cranesbill, Musk Mallow, Ox-eye daisy, Foxgloves, Small Scabious and Field Scabious