• GENERAL DISTRIBUTION
• ECOSYSTEMS
• STATES
• BLM PHYSIOGRAPHIC REGIONS
• KUCHLER PLANT ASSOCIATIONS
• SAF COVER TYPES
• SRM (RANGELAND) COVER TYPES
• HABITAT TYPES AND PLANT COMMUNITIES

GENERAL DISTRIBUTION:

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]):

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.

ECOSYSTEMS [31]:

STATES:

BLM PHYSIOGRAPHIC REGIONS [11]:

KUCHLER [42] PLANT ASSOCIATIONS:

SAF COVER TYPES [27]:

SRM (RANGELAND) COVER TYPES [70]:

HABITAT TYPES AND PLANT COMMUNITIES:

Pacific Northwest:
In eastern Washington, the most common associate of Russian knapweed is basin wildrye (Leymus cinereus) [75]. In this area, Russian knapweed occurs in big sagebrush (Artemisia tridentata)/bluebunch wheatgrass (Pseudoroegneria spicata), black greasewood (Sarcobatus vermiculatus)/saltgrass (Distichlis spicata) and basin wildrye/saltgrass habitat types [59]. Russian knapweed may also be found in the big sagebrush/basin wildrye habitat type in Oregon [56].

In Idaho, Russian knapweed may be found with bluebunch wheatgrass, Idaho fescue (Festuca idahoensis), snowberry (Symphoricarpos spp.), and rose (Rosa spp.). In this area it may threaten rare plants such as Spalding's silene (Silene spaldingii), smallhead goldenweed (Pyrrocoma liatriformis), sagebrush Mariposa lily (Calochortus macrocarpus var. maculosus), and Idaho hawksbeard (Crepis bakeri ssp. idahoensis) [56].

In Montana, Russian knapweed was found growing in alfalfa and grain fields in Missouri River bottomlands in the north-central part of the state. Vegetation in the area included sagebrush (Artemisia spp.)-grassland (where dominants included western wheatgrass (Pascopyrum smithii), smooth brome (Bromus inermis), and Canada wildrye (Elymus canadensis)); black greasewood; plains cottonwood (Populus deltoides ssp. monilifera); willow (Salix spp.) and "meadow" types. Plants associated with Russian knapweed included barley (Hordeum spp.), witchgrass (Panicum capillare), green bristlegrass (Setaria viridis), pigweed (Amaranthus spp.), Chenopodium spp., old-man's-whiskers (Geum triflorum), summer-cypress (Kochia scoparia), and common dandelion (Taraxacum officinale) [1]. Of 21 diverse sites in southwestern Montana dominated by curlleaf mountain-mahogany (Cercocarpus ledifolius), Russian knapweed occurred on 2 sites west of the Continental Divide in 1975 [26].

Middle Rocky Mountains:
In Wyoming Russian knapweed occurs on perennial grasslands dominated by blue grama (Bouteloua gracilis) [17].

In Colorado the most severe infestations of Russian knapweed occur in mountain and western slope counties, with lighter infestations associated with blue grama on the eastern plains [17]. Habitats in which Russian knapweed may be found include riparian woodlands dominated by cottonwood (Populus spp.), skunkbush sumac, and willow; riparian shrubland; and sagebrush/fourwing saltbush (Atriplex canescens) shrublands.

Related categories for SPECIES: Acroptilon repens | Russian Knapweed