How did Russian knapweed get to the US?

Rhaponticum repens entered the United States around 1900 possibly as a contaminant of alfalfa seed from the former Russian Turkestan region of Asia. Once imported, Russian knapweed was easily spread by the sale of domestically produced alfalfa seed or hay containing knapweed seeds.

Is Russian knapweed poisonous?

Russian knapweed (Centaurea repens) is a perennial weed which is poisonous to horses. The continued foraging of Russian knapweed builds the toxin level in your horse’s body. Knapweed poisoning symptoms usually occur once the horse has ingested 60% of his body weight of toxin.

Where is Russian knapweed found?

Habitat: Native to Eurasia specifically southern Ukraine, southeast Russia, Iran and Mongolia. Found in disturbed sites, along roadsides, riverbanks, irrigation ditches, pastures, waste places, clear-cuts, and croplands.

What kills Russian knapweed?

Russian knapweed is best controlled with a selective, postemergent herbicide. Typically, the main herbicide entry into the plant is through the leaves and stems; but certain herbicides can enter through the roots.

What is the scientific name for Russian knapweed?

Rhaponticum repens
Rhaponticum repens/Scientific names

Rhaponticum repens (L.) Hidalgo ( ITIS ) Synonym: Centaurea repens (L.), Acroptilon repens (L.)

Why is Russian knapweed bad?

Definition. Yellow star thistle and Russian knapweed cause a unique syndrome in horses characterized by the inability to prehend and chew food because of hypertonicity of the facial muscles. Prolonged continuous consumption of either plant is necessary to produce this irreversible and ultimately fatal poisoning.

Is knapweed OK in hay?

Her hay is not very good but no potentially dangerous plants. I would now say to anyone as a precaution don’t let knapweed of any variety contaminate your hay.

What does Russian knapweed look like?

Russian knapweed (Rhaponticum repens) is a bushy, branched perennial in the Aster family reaching 1 to 3 feet tall and forming clones or colonies from vigorous, deep, spreading rhizomes. It has numerous, small, thistle like flower heads that are pink to purple in color.

Is knapweed annual or perennial?

Diffuse knapweed (Centaurea diffusa) is a short-lived perennial, a biennial, or occasionally an annual. It reproduces and spreads from seed. The plant develops a single shoot (stem), 1 to 2 feet tall or more, that is branched toward the top (Figure 1). Grazed plants may produce multiple stems.

How do you manage knapweed?

Knapweed can be controlled using specific herbicides. Knapweed should be sprayed in spring or early summer before flower buds appear to ensure plants do not produce seed after being sprayed. Spraying can also be done in the fall, to target rosettes that will overwinter.

How can you tell a Russian knapweed?

Leaves at the base of the stem (basal leaves) are gray-green and lobed. Upper stem leaves are smaller with toothed edges or entire (smooth) edges. Stems are upright, branched and hairy. Young plants are whitish and woolly.

What does spotted knapweed look like?

Grows 2- 4 feet tall and has a long tap root. Foliage is gray-green. Flowers are small, oval, pink to purple, produced at the end of branched stems and covered with stiff bracts marked with dark, upside-down “V” markings, giving them a spotted appearance. Blooming occurs from June through August.