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Diffuse Knapweed

Centaurea diffusa Lam.

Asteraceae (Sunflower Family)

▲▼ seedlings

▲▼ seedlings

▲▼ young plants

▲▼ young plants

▲▼ young plants

▲▼ first year rosettes

▲ ▼ mature, flowering plants

▲ flowering stem showing white flowers

▲▼inflorescences, with above showing the comb-like spines on the bracts

▲▼ inflorescences

▲▼ large colonies of diffuse knapweed in Arizona

 

 

 

Centaurea diffusa Lam., Diffuse Knapweed: (Bayer Code:  CENDI; US Code CEDI3)

·         Annual, biennial or perennial, with basal rosette followed by much-branched flowering stems

·         Basal leaves leaves similar to spotted knapweed

·         Has inflorescence with 12-13 white ray flowers per head and tan, comb-like, toothed bracts under inflorescence

·         Not common in eastern Midwest, but common in near & west of Rocky Mountains

·         Highly-invasive in open prairie and rangeland soils, plus is allelopathic to other plants

·         Prefers full sun, well-drained soils

·         Similar species:

      o   Spotted knapweed (Centaurea stoebe) has similar basal leaves, but has pink flowers and a dark spot on the bracts below the flower head

      o   Squarrose knapweed (Centaurea virgata) has somewhat similar leaves and also has tan, comb-like bracts below the head, but squarrose knapweed’s bract tips point away more from the head, plus squarrose knapweed has pink flowers

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Updated 19 January 2019