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

GENERAL DISTRIBUTION:

The decrease in acreage reported in Montana is attributed to improved inventory methods during the past decade. Although inventories are more common and more accurate, 50% of these states reported only 50% accuracy, while 31% reported 51 to 75% accuracy, and 2 states reported 75 to 100% accuracy [33]. Watson and Renney [221] reported that spotted knapweed was abundant in British Columbia, common in Ontario, Quebec and the Maritimes, and observed in southern Alberta in 1974.

Information on the distribution of spotted knapweed is limited for most North American states and provinces in which it occurs. It is commonly listed as occurring on roadsides and other disturbed areas in the Adirondacks [93], New England [170], the Northeast [45], Michigan [217], Illinois [125], Nebraska [165], the Great Plains [48], the Blue Ridge region of North Carolina, Tennessee, and Virginia [231], West Virginia [197], the Carolinas [149], and Florida [5,233].

Specific information on the plant communities in which spotted knapweed occurs is also limited outside its primary area of occurrence. The following lists reflect ecosystems and cover types in which spotted knapweed is commonly found, although the lists are not exhaustive.

ECOSYSTEMS [43]:

STATES:

BLM PHYSIOGRAPHIC REGIONS [15]:

KUCHLER [92] PLANT ASSOCIATIONS:

SAF COVER TYPES [36]:

SRM (RANGELAND) COVER TYPES [180]:

HABITAT TYPES AND PLANT COMMUNITIES:

Spotted knapweed is listed as a "dominance type" in Montana riparian areas and is found primarily on upper terraces of major river courses, relatively dry, disturbed sites, and gravel bars. Associated species are affected by the degree of past disturbance. On relatively undisturbed sites it may be found with bluebunch wheatgrass, redtop (Agrostis spp.), silver sagebrush (Artemisia cana), Idaho fescue and Wood's rose (Rosa woodsii). On more disturbed sites likely associates include Canada bluegrass (Poa compressa), Kentucky bluegrass, bulbous bluegrass (P. bulbosa), slender cinquefoil (Potentilla gracilis), crested wheatgrass (Agropyron cristatum), and Canada thistle (Cirsium arvense) [57]. It may occur with other species associated with frequent disturbance such as common tansy (Tanacetum vulgare), creeping bentgrass (Agrostis stolonifera), and widely scattered seedlings of sandbar willow (Salix exigua) and black cottonwood (Populus balsamifera ssp. trichocarpa) [55]. Hansen and others [56] list spotted knapweed occurring in 24 riparian habitat types in Montana. Dominant associates include red-osier dogwood (Cornus sericea), black cottonwood, grand fir (Abies grandis), ladyfern (Athyrium filix-femina), spruce (Picea spp.), Douglas-fir, Rocky Mountain juniper (Juniperus scopulorum), ponderosa pine, quaking aspen (Populus tremuloides), narrowleaf cottonwood (P. angustifolia), Geyer willow (Salix geyeriana), sandbar willow, Wood's rose, thinleaf alder (Alnus incana ssp. tenuifolia), water birch (Betula occidentalis), shrubby cinquefoil (Potentilla fruticosa), chokecherry (Prunus virginiana), western snowberry (Symphoricarpos occidentalis), water sedge (Carex aquatilis), Baltic rush (Juncus balticus), and reed canarygrass (Phalaris arundinacea).

In Washington state, spotted knapweed is found in openings in ponderosa pine/bunchgrass or Douglas-fir/shrub forests, especially on coarse, gravelly glacial soils [163]. Spotted knapweed is competitive in disturbed forest types in Washington (primarily northeastern), including ponderosa pine with bunchgrass, snowberry (Symphoricarpos spp.), or ninebark (Physocarpus malvaceus); or Douglas-fir with snowberry or ninebark [164].

Plants associated with spotted knapweed in British Columbia are characteristic of dryland range and pioneer sites including bluebunch wheatgrass, rough and Idaho fescue, bluegrass (Poa spp.), and many others [221]. Bluebunch wheatgrass communities in British Columbia are especially susceptible to spotted knapweed infestation [2]. In west-central British Columbia, an infestation of spotted knapweed occurred along the railroad with Kentucky bluegrass, red fescue (Festuca rubra), timothy, smooth brome, and clover (Trifolium spp.) [236]. In open forests of British Columbia, spotted knapweed may be found with ponderosa pine, Douglas-fir, ninebark, Saskatoon serviceberry (Amelanchier alnifolia), mock orange (Philadelphus lewisii), toadflax (Linaria dalmatica), pinegrass, and Idaho fescue [124]; or with lodgepole pine (Pinus contorta), Engelmann spruce (Picea engelmannii), subalpine fir, huckleberry (Vaccinium spp.) and fireweed (Epilobium angustifolium) [148].

Information on plant communities invaded by spotted knapweed in other parts of the country is very limited. In North Dakota spotted knapweed is found primarily along roads and sometimes in adjacent grasslands [17]. In Michigan oldfields it is found growing with blackberry (Rubus alleghaniensis), poverty oatgrass (Danthonia spicata), and broomsedge (Andropogon virginicus) [40]. In Shenandoah National Park, Virginia, spotted knapweed was found growing along a trail in the bigfruit hawthorn (Crataegus macrosperma)/shrub forest with black raspberry (R. occidentalis) and dwarf cinquefoil (Potentilla canadensis) [54]. Spotted knapweed is said to be widespread in California, occurring in disturbed areas up to 6,600 feet (2,012 m) [67,185]. In Yellowstone National Park it is found in a campground in a big sagebrush (Artemisia tridentata)/bluebunch wheatgrass habitat type [4].

Related categories for SPECIES: Centaurea stoebe ssp. micranthos | Spotted Knapweed