- Russian knapweed
(Centaurea repens L.)
(Acroptilon repens), Asteraceae.
Weed ID Links Young Plant Flowers Plants Plant With Root Flower Bud Seedheads-Old More Plants
Roots: the roots are horizontal and vertical (up and down, and left to right) in the ground, they may be black and the roots also creep, the roots can be from 6 to 27 roots per square foot (3), they also can grow to a depth of 23 feet. (3)
Photo by Ron Lang, USDA-APHIS-PPQ. WY.
Stems/Leaves: the stems are erect and branched openly, they can be from 18 to 36 inches tall. Lower leaves are 2 to 4 inches long and the upper leaves are very narrow. The stems can also be ridged and stiff and branched, the younger stems are covered with the soft gray hairs, the upper leaves are small also, leaves that are at the middle of the stem have toothed margins. (2)
Flowers: the flowers are cone-shaped and the heads are 1/4 to ½ inches in diameter. They are solitary at the tip of the stem, the ray flowers are pink to lavender, they can be un-shaded, when they mature the color becomes a straw color in the fall, they are borne on branch tips during the summer and the fall. Flowering occurs from June to August. (5)
Fruits/Seeds: the flowers have a thistle like texture, are 1/3 to 1/4" in diameter and are lavender to white in color. The seeds are flattened, ivory color, 2-3 mm long, 2 mm broad, 1 mm thick, and have small bristles. The bristles of the seeds are white. (5)
Methods of Reproduction: it reproduce by creeping roots and by seeds. (1)
Montana Infestation:
Environments of Infestations: Russian knapweed will grow in cultivated fields, fence rows, roadsides, along ditch banks, and in wasted places (1), it can occur in most soils in the U.S. (4)
Comments: Russian knapweed is a very large problem that is growing within the United States. This noxious weed is a problem that everyone needs to work to control. This summer I personally spent time spraying the weed and I think it is a problem.
Impacts: Russian knapweed is very poisonous to horses and it will give them a chewing disease. (2)
Native Range: It is a native of Eurasia and was probably introduced in 1898.