Also known as white knapweed and tumble knapweed was introduced here as a contaminant of alfalfa from the caspian sea region of turkistan. Diffuse knapweed has hairy greyish green split leaves on many branches growing from a single upright stem.
Spotted knapweed on the other hand has pink to purplish flowers with prominent black spots on the bracts beneath.
Diffuse knapweed flower. Leaves are small elliptical yellow to brown bracts surround the flowers. Russian knapweed rhaponticum repens l hidalgo. Biological control agents available for diffuse knapweed are.
Diffuse knapweed a class b designate noxious weed in franklin county washington centaurea diffusa is of the asteraceae family. Diffuse knapweed flowers and sets seed in late summer or fall. The flowers can be white or purple so flower color is not a distinguishing feature between knapweed species figure 5.
This plant is a prolific seed producer. Diffuse finely dissected compound white flowers. Agapeta zoegana the sulfur knapweed moth that have root mining larvae.
The flowers are white or sometimes purple with small sharp rigid spines on the bracts. Cyphocleonus achates the knapweed root weevil which has root mining larvae larvae feeding within the roots. It can quickly take over both disturbed and managed areas outcompeting native species and reducing plant diversity and wildlife habitat.
Diffuse knapweed bracts have a rigid terminal spine about one third of an inch long with four to five pairs of shorter lateral spines figures 3 and 4. Larinus minutus the seedhead feeding weevil. Sphenoptera jugoslavica the bronze knapweed root borer that have larvae that bore into and tunnel within knapweed roots.
Bangasternus fausti the broad nosed seedhead weevil that have seed feeding larvae. The spiny bracts resemble a crab in appearance are very sharp and can puncture skin if touched. Sunflower or aster family asteraceae reasons for concern.
It then breaks off at the base and becomes a tumbleweed spreading seed far and wide. Diffuse knapweed cannot tolerate cultivation or excessive moisture and is therefore uncommon on cultivated land. Spotted pink to purple finely dissected compound daisy flowers with black fringe.
Diffuse knapweed centaurea diffusa is a biennial or short lived perennial that forms a basal rosette in its first year and bolts during second year growth. Knapweed is more intolerant to dense shade and prefers moister habitats than diffuse knapweed. When mature this knapweed tends to be shorter than other knapweeds usually reaching one to three feet in height.
However spotted knapweed is still a problem in forested areas disturbed by logging fire or other factors. Diffuse knapweed is an annual or biennial plant generally growing to between 10 and 60 cm in height it has a highly branched stem and a large taproot as well as a basal rosette of leaves with smaller leaves alternating on the upright stems. Diffuse knapweed flowers from july to september.
Spotted knapweed has hairy deeply cut leaves and purple flowers occasionally white on one or more upright stems. Flowers are usually white or pink and grow out of urn shaped heads carried at the tips of the many branches. Can be pink to purple.
Diffuse knapweed is a biennial or short lived peren nial species with a. Height to 4 ft. State designated noxious weed.