Distribution
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Russian knapweed is native to Mongolia, western Turkestan, Iran, Turkish Armenia, and Asia Minor [45], and is found in cultivated fields and dry pastures of the southern Ukraine, southeastern Russia, and western Kazakhstan. It is considered a serious weed of dryland crops in the southern parts of the former Soviet Republics ([83], and sources therein). Russian knapweed was initially introduced to North America in the early 1900's, primarily as a contaminant of Turkestan alfalfa (Medicago sativa) seed (Groh 1940, as cited by [83]) and possibly sugarbeet (Beta vulgaris) seed (Robbins and others 1951, as cited by [45]). Rogers [61] suggests that Russian knapweed is likely to have established wherever Turkestan alfalfa has been planted. Its spread from these locations is linked to the distribution of knapweed-infested hay [61,83].
Russian knapweed is widespread in the U.S. and especially common in the semiarid portions of the western states and adjacent Canada. Maddox and others [45] reported infestations in South Dakota, Minnesota, and Virginia in 1985, and current distribution maps indicate its occurrence in several midwestern and Great Plains states [40,77]. The Plants database provides a distribution map of Russian knapweed in the United States.
The following table reflects estimates of Russian knapweed acreage as reported by surveyed states or provinces in 1988 and again in 2000 (from [25]):
| State/Province | 1988 Acreage | 2000 Acreage |
| Arizona | not reported | 5,500 |
| California | not reported | 150 |
| Colorado | 50,000 | 168,000 |
| Idaho | 890,000 | 425,000 |
| Kansas | not reported | 5 |
| Montana | 47,893 | 64,456 |
| Nevada | not reported | 75,000 |
| New Mexico | not reported | 15,000 |
| North Dakota | 250 | 436 |
| Oregon | 15,000 | 85,000 |
| South Dakota | 3,045 | 2,717 |
| Utah | 150,000 | 60,000 |
| Washington | 8,050 | 500,000 |
| Wyoming | 200,000 | 160,000 |
| Alberta | 20 | scattered |
| British Columbia | not reported | 450 |
| Total | 1,561,714 |
Although inventories are more common and more accurate in the year 2000 than in 1988, 50% of these states reported only 50% accuracy, while 31% reported 51 to 75% accuracy, and 2 states reported 75 to 100% accuracy in the 2000 survey [25].
The following biogeographic classification systems are presented as a guide to demonstrate where Russian knapweed might be found based on reported occurrence and biological tolerance to factors that are likely to limit its distribution. Precise distribution information is limited, especially in the southwestern, central, midwestern, and eastern states. Therefore, these lists are speculative and not exhaustive.
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