Thorson Prairie WMA






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There is a 58.5-acre plot of cultivated row cropland in the north section.


















Printable Map(s) with GPS coordinates


North Section

  Printable map   Printable map  

Central Section

  South Section  
  Printable map   Printable map  



1,109.12 acres




There are six designated parking areas:

CR 44 (160th Ave. SW)
N47 40.502, W96 23.703

170th Ave. SW
N47 40.733, W96 25.000

340th St. SW
N47 40.389, W96 24.662

350th St. SW (West)
N47 39.553, W96 24.884

350th St. SW (East)
N47 39.535, W96 24.797

MN Hwy 102
N47 38.406, W96 24.875


Driving Directions

  Area and County  

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          Polk County  
          Northwest Minnesota  

Hiking Trails


The 52-mile Agassiz Recreational Trail, an off-highway vehicle (OHV) trail, passes through this WMA on an old railroad bed closely paralleling MN Highway 102.




Deer, Small Game, Doves. See Hunting and Trapping Regulations (MN DNR) for details.


Ecological Classification

  Ecological Classification  
  Ecological Province    

Tallgrass Aspen Parklands

  Ecological Section    

Lake Agassiz, Aspen Parklands

  Ecological Subsection    

Aspen Parklands

  Land Type Association    

Beach Ridges

Gentilly Lake Plain


Native Plant Communities*


Agassiz Interbeach Prairie Complex

Calcareous Fen (Northwestern)

Dry Sand - Gravel Prairie (Northern)

Mesic Prairie (Northern)

Northwestern Wet-Mesic Aspen Woodland

Seepage Meadow/Carr

Seepage Meadow/Carr: Tussock Sedge Subtype

Wet Brush-Prairie (Northern)

Wet Prairie (Northern)

Wet Seepage Prairie (Northern)

  * Source: The Minnesota Biological Survey, Minnesota Department of Natural Resources, Division of Ecological Resources      

Natural Features








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There are two parking lots on 350th St. SW.

  Thorson Prairie WMA  

The west lot on the north side of the road is well concealed behind tall shrubs.

  Thorson Prairie WMA  

The east lot on the south side of the road is larger and easy to find at the top of the hill.

  Thorson Prairie WMA  


    Thorson Prairie WMA   Thorson Prairie WMA  

Gravel Pit

    Thorson Prairie WMA      

Other Prairie

    Thorson Prairie WMA      






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One bird species with conservation status in Minnesota has been seen here:

Special Concern

Greater Prairie-chicken (Tympanuchus cupido)


Black-capped Chickadee (Poecile atricapillus)

Cedar Waxwing (Bombycilla cedrorum)

Gray Catbird (Dumetella carolinensis)

House Finch (Haemorhous mexicanus)

  Cedar Waxwing  

Fungi and Lichens

  Black Knot (Apiosporina morbosa)   Black Knot  

Insects and Arachnids


bald-faced hornet (Dolichovespula maculata)

Carolina grasshopper (Dissosteira carolina)

deer fly (Chrysops mitis)

dog day cicada (Neotibicen canicularis)

dusky stink bug (Euschistus tristigmus luridus)

goldenrod bunch gall midge (Rhopalomyia solidaginis)

goldenrod gall fly (Eurosta solidaginis)

monarch (Danaus plexippus)

multicolored Asian lady beetle (Harmonia axyridis)

seven-spotted lady beetle (Coccinella septempunctata)

willow pinecone gall midge (Rabdophaga strobiloides)


Carolina grasshopper

dog day cicada





One mammal species with conservation status in Minnesota have been seen here:

Special Concern

moose (Alces americanus)

  plains pocket gopher (Geomys bursarius)   plains pocket gopher  



Seven plant species with conservation status in Minnesota are found here:


woolly groundsel (Packera cana)


sterile sedge (Carex sterilis)

Special Concern

blanket flower (Gaillardia aristata)

creeping juniper (Juniperus horizontalis)

red three-awn (Aristida purpurea var. longiseta)

small white lady’s slipper (Cypripedium candidum)

spikeoat (Avenula hookeri)


Minnesota Biodiversity Atlas and Minnesota Biological Survey Vegetation Releves Plant List


Plants frequently found in:

Calcareous Fen (Northwestern) OPp93a

Dry Sand - Gravel Prairie (Northern) UPn12b

Mesic Prairie (Northern) UPn23b

Northwestern Wet-Mesic Aspen Woodland FDw44

Seepage Meadow/Carr WMs83a

Seepage Meadow/Carr: Tussock Sedge Subtype WMs83a1

Wet Brush-Prairie (Northern) WPn53b

Wet Prairie (Northern) WPn53c

Wet Seepage Prairie (Northern) WPn53a



alfalfa (Medicago sativa ssp. sativa)

American common reed (Phragmites australis ssp. americanus)

arctic brome (Bromus kalmii)

American bugleweed (Lycopus americanus)

asparagus (Asparagus officinalis)

Balkan catchfly (Silene csereii)

Baltic rush (Juncus balticus var. littoralis)

bastard toadflax (Comandra umbellata ssp. umbellata)

bearded wheatgrass (Elymus trachycaulus ssp. subsecundus)

Bebb’s willow (Salix bebbiana)

big bluestem (Andropogon gerardi)

bird’s-foot trefoil (Lotus corniculatus var. corniculatus)

black-eyed Susan (Rudbeckia hirta var. pulcherrima)

blue grama (Bouteloua gracilis)

blue-eyed grass (Sisyrinchium sp.)

bog birch (Betula pumila)

bottle gentian (Gentiana andrewsii)

boxelder (Acer negundo var. negundo)

broad-leaved cattail (Typha latifolia)

Buxbaum’s sedge (Carex buxbaumii)

Canada anemone (Anemonastrum canadense)

Canada thistle (Cirsium arvense)

Canadian tick-trefoil (Desmodium canadense)

chokecherry (Prunus virginiana var. virginiana)

common evening primrose (Oenothera biennis)

common lilac (Syringa vulgaris)

common milkweed (Asclepias syriaca)

common mullein (Verbascum thapsus ssp. thapsus)

common sneezeweed (Helenium autumnale)

crown vetch (Securigera varia)

dark green bulrush (Scirpus atrovirens)

dotted blazing star (Liatris punctata var. punctata)

falsegold groundsel (Packera pseudaurea var. semicordata)

flat-topped aster (Doellingeria umbellata)

Flodman’s thistle (Cirsium flodmanii)

four-flowered yellow loosestrife (Lysimachia quadriflora)

giant goldenrod (Solidago gigantea)

giant sunflower (Helianthus giganteus)

golden alexanders (Zizia aurea)

golden ragwort (Packera aurea)

grass-leaved goldenrod (Euthamia graminifolia)

gray goldenrod (Solidago nemoralis)

green milkweed (Asclepias viridiflora)

grimmia dry rock moss (Grimmia laevigata)

grooved yellow flax (Linum sulcatum var. sulcatum)

hairy false goldenaster (Heterotheca villosa)

hairy panic grass (Dichanthelium acuminatum)

harebell (Campanula rotundifolia)

hoary alyssum (Berteroa incana)

hybrid cattail (Typha × glauca)

Indian hemp (Apocynum cannabinum)

Indiangrass (Sorghastrum nutans)

June grass (Koeleria macrantha)

Kalm’s lobelia (Lobelia kalmii)

Kentucky bluegrass (Poa pratensis ssp. pratensis)

leadplant (Amorpha canescens)

lesser fringed gentian (Gentianopsis virgata ssp. virgata)

little bluestem (Schizachyrium scoparium)

long-headed coneflower (Ratibida columnifera)

marsh arrow-grass (Triglochin palustris)

Maximilian’s sunflower (Helianthus maximiliani)

narrow-leaved cattail (Typha angustifolia)

narrow-leaved purple coneflower (Echinacea angustifolia)

needle-and-thread (Hesperostipa comata ssp. comata)

New England aster (Symphyotrichum novae-angliae)

northern bog aster (Symphyotrichum boreale)

northern plains blazing star (Liatris ligulistylis)

Nuttall’s little rose (Chamaerhodos erecta ssp. nuttallii)

panicled aster (Symphyotrichum lanceolatum)

peachleaf willow (Salix amygdaloides)

Pennsylvania cinquefoil (Potentilla pensylvanica)

perennial sow thistle (Sonchus arvensis)

plains cottonwood (Populus deltoides ssp. molinifera)

plains muhly (Muhlenbergia cuspidata)

plumeless thistle (Carduus acanthoides ssp. acanthoides)

poke milkweed (Asclepias exaltata)

porcupine grass (Hesperostipa spartea)

prairie alumroot (Heuchera richardsonii)

prairie blazing star (Liatris pycnostachya var. pycnostachya)

prairie cordgrass (Sporobolus michauxianus)

prairie dropseed (Sporobolus heterolepis)

prairie goldenrod (Solidago ptarmicoides)

prairie onion (Allium stellatum)

prairie rose (Rosa arkansana)

prairie sagewort (Artemisia frigida)

prairie wedge grass (Sphenopholis obtusata)

prairie willow (Salix humilis)

purple meadow-rue (Thalictrum dasycarpum)

purple prairie clover (Dalea purpurea var. purpurea)

purple-stem aster (Symphyotrichum puniceum var. puniceum)

pussy willow (Salix discolor)

quackgrass (Elymus repens)

quaking aspen (Populus tremuloides)

red clover (Trifolium pratense)

red osier dogwood (Cornus sericea ssp. sericea)

red three-awn (Aristida purpurea var. longiseta)

Riddell’s goldenrod (Solidago riddellii)

rough blazing star (Liatris aspera)

sage-leaved willow (Salix candida)

sand cherry (Prunus pumila)

sandbar willow (Salix interior)

scouring rush horsetail (Equisetum hyemale ssp. affine)

seaside arrowgrass (Triglochin maritima)

shorthair goldenrod (Solidago altissima var. gilvocanescens)

shrubby cinquefoil (Dasiphora fruticosa ssp. floribunda)

Siberian elm (Ulmus pumila)

sideoats grama (Bouteloua curtipendula var. curtipendula)

silky aster (Symphyotrichum sericeum)

slender wheatgrass (Elymus trachycaulus ssp. trachycaulus)

slender willow (Salix petiolaris)

slender-leaf false foxglove (Agalinis tenuifolia)

slim-stem reedgrass (Calamagrostis stricta)

small white lady’s slipper (Cypripedium candidum)

smooth brome (Bromus inermis)

smooth sumac (Rhus glabra)

spiked muhly (Muhlenbergia glomerata)

spikeoat (Avenula hookeri)

spotted Joe Pye weed (Eutrochium maculatum)

spotted knapweed (Centaurea stoebe ssp. micranthos)

spotted water hemlock (Cicuta maculata)

sterile sedge (Carex sterilis)

sticky false asphodel (Triantha glutinosa)

stiff goldenrod (Solidago rigida ssp. rigida)

stiff sunflower (Helianthus pauciflorus ssp. subrhomboideus)

sulphur cinquefoil (Potentilla recta)

swamp betony (Pedicularis lanceolata)

swamp milkweed (Asclepias incarnata ssp. incarnata)

swamp thistle (Cirsium muticum)

tall cinquefoil (Drymocallis arguta)

tarragon (Artemisia dracunculus)

toothed evening primrose (Oenothera serrulata)

Torrey’s rush (Juncus torreyi)

tufted hairgrass (Deschampsia cespitosa)

Virginia mountain mint (Pycnanthemum virginianum)

water horsetail (Equisetum fluviatile)

western marbleseed (Lithospermum occidentale)

white heath aster (Symphyotrichum ericoides var. ericoides)

white rattlesnake root (Nabalus albus)

white sage (Artemisia ludoviciana ssp. ludoviciana)

white sweet clover (Melilotus albus)

Wilcox’s panic grass (Dichanthelium wilcoxianum)

wild licorice (Glycyrrhiza lepidota)

wild strawberry (Fragaria virginiana)

wolfberry (Symphoricarpos occidentalis)

woodbine (Parthenocissus vitacea)

woolly cinquefoil (Potentilla hippiana)

woolly groundsel (Packera cana)


Acer negundo var. negundo (boxelder)

Agalinis tenuifolia (slender-leaf false foxglove)

Allium stellatum (prairie onion)

Amorpha canescens (leadplant)

Andropogon gerardi (big bluestem)

Anemonastrum canadense (Canada anemone)

Apocynum cannabinum (Indian hemp)

Aristida purpurea var. longiseta (red three-awn)

Artemisia dracunculus (tarragon)

Artemisia frigida (prairie sagewort)

Artemisia ludoviciana ssp. ludoviciana (white sage)

Asclepias exaltata (poke milkweed)

Asclepias incarnata ssp. incarnata (swamp milkweed)

Asclepias syriaca (common milkweed)

Asclepias viridiflora (green milkweed)

Asparagus officinalis (asparagus)

Avenula hookeri (spikeoat)

Berteroa incana (hoary alyssum)

Betula pumila (bog birch)

Bouteloua curtipendula var. curtipendula (sideoats grama)

Bouteloua gracilis (blue grama)

Bromus inermis (smooth brome)

Bromus kalmii (arctic brome)

Calamagrostis stricta (slim-stem reedgrass)

Campanula rotundifolia (harebell)

Carduus acanthoides (plumeless thistle)

Carex buxbaumii (Buxbaum’s sedge)

Carex sterilis (sterile sedge)

Centaurea stoebe ssp. micranthos (spotted knapweed)

Chamaerhodos erecta ssp. nuttallii (Nuttall’s little rose)

Cicuta maculata (spotted water hemlock)

Cirsium arvense (Canada thistle)

Cirsium flodmanii (Flodman’s thistle)

Cirsium muticum (swamp thistle)

Comandra umbellata ssp. umbellata (bastard toadflax)

Cornus sericea ssp. sericea (red osier dogwood)

Cypripedium candidum (small white lady’s slipper)

Dalea purpurea var. purpurea (purple prairie clover)

Dasiphora fruticosa ssp. floribunda (shrubby cinquefoil)

Deschampsia cespitosa (tufted hairgrass)

Desmodium canadense (Canadian tick-trefoil)

Dichanthelium acuminatum (hairy panic grass)

Dichanthelium wilcoxianum (Wilcox’s panic grass)

Doellingeria umbellata (flat-topped aster)

Drymocallis arguta (tall cinquefoil)

Echinacea angustifolia (narrow-leaved purple coneflower)

Elymus repens (quackgrass)

Elymus trachycaulus ssp. subsecundus (bearded wheatgrass)

Elymus trachycaulus ssp. trachycaulus (slender wheatgrass)

Equisetum fluviatile (water horsetail)

Equisetum hyemale ssp. affine (scouring rush horsetail)

Euthamia graminifolia (grass-leaved goldenrod)

Eutrochium maculatum (spotted Joe Pye weed)

Fragaria virginiana (wild strawberry)

Gentiana andrewsii (bottle gentian)

Gentianopsis virgata ssp. virgata (lesser fringed gentian)

Glycyrrhiza lepidota (wild licorice)

Grimmia laevigata (grimmia dry rock moss)

Helenium autumnale (common sneezeweed)

Helianthus giganteus (giant sunflower)

Helianthus maximiliani (Maximilian’s sunflower)

Helianthus pauciflorus ssp. subrhomboideus (stiff sunflower)

Hesperostipa comata ssp. comata (needle-and-thread)

Hesperostipa spartea (porcupine grass)

Heterotheca villosa (hairy false goldenaster)

Heuchera richardsonii (prairie alumroot)

Juncus balticus var. littoralis (Baltic rush)

Juncus torreyi (Torrey’s rush)

Koeleria macrantha (June grass)

Liatris aspera (rough blazing star)

Liatris ligulistylis (northern plains blazing star)

Liatris punctata var. punctata (dotted blazing star)

Liatris pycnostachya var. pycnostachya (prairie blazing star)

Linum sulcatum var. sulcatum (grooved yellow flax)

Lithospermum occidentale (western marbleseed)

Lobelia kalmii (Kalm’s lobelia)

Lotus corniculatus var. corniculatus (bird’s-foot trefoil)

Lycopus americanus (American bugleweed)

Lysimachia quadriflora (four-flowered yellow loosestrife)

Medicago sativa ssp. sativa (alfalfa)

Melilotus albus (white sweet clover)

Muhlenbergia cuspidata (plains muhly)

Muhlenbergia glomerata (spiked muhly)

Nabalus albus (white rattlesnake root)

Oenothera biennis (common evening primrose)

Oenothera serrulata (toothed evening primrose)

Solidago riddellii (Riddell’s goldenrod)

Packera aurea (golden ragwort)

Packera cana (woolly groundsel)

Packera pseudaurea var. semicordata (falsegold groundsel)

Parthenocissus vitacea (woodbine)

Pedicularis lanceolata (swamp betony)

Phragmites australis ssp. americanus (American common reed)

Poa pratensis ssp. pratensis (Kentucky bluegrass)

Populus deltoides ssp. molinifera (plains cottonwood)

Populus tremuloides (quaking aspen)

Potentilla hippiana (woolly cinquefoil)

Potentilla pensylvanica (Pennsylvania cinquefoil)

Potentilla recta (sulphur cinquefoil)

Prunus pumila (sand cherry)

Prunus virginiana var. virginiana (chokecherry)

Pycnanthemum virginianum (Virginia mountain mint)

Ratibida columnifera (long-headed coneflower)

Rhus glabra (smooth sumac)

Rosa arkansana (prairie rose)

Rudbeckia hirta var. pulcherrima (black-eyed Susan)

Salix amygdaloides (peachleaf willow)

Salix bebbiana (Bebb’s willow)

Salix candida (sage-leaved willow)

Salix discolor (pussy willow)

Salix humilis (prairie willow)

Salix interior (sandbar willow)

Salix petiolaris (slender willow)

Schizachyrium scoparium (little bluestem)

Scirpus atrovirens (dark green bulrush)

Securigera varia (crown vetch)

Silene csereii (Balkan catchfly)

Sisyrinchium sp. (blue-eyed grass)

Solidago altissima var. gilvocanescens (shorthair goldenrod)

Solidago gigantea (giant goldenrod)

Solidago nemoralis (gray goldenrod)

Solidago ptarmicoides (prairie goldenrod)

Solidago rigida ssp. rigida (stiff goldenrod)

Sonchus arvensis (perennial sow thistle)

Sorghastrum nutans (Indiangrass)

Sphenopholis obtusata (prairie wedge grass)

Sporobolus heterolepis (prairie dropseed)

Sporobolus michauxianus (prairie cordgrass)

Symphoricarpos occidentalis (wolfberry)

Symphyotrichum boreale (northern bog aster)

Symphyotrichum ericoides var. ericoides (white heath aster)

Symphyotrichum lanceolatum (panicled aster)

Symphyotrichum novae-angliae (New England aster)

Symphyotrichum puniceum var. puniceum (purple-stem aster)

Symphyotrichum sericeum (silky aster)

Syringa vulgaris (common lilac)

Thalictrum dasycarpum (purple meadow-rue)

Triantha glutinosa (sticky false asphodel)

Trifolium pratense (red clover)

Triglochin maritima (seaside arrowgrass)

Triglochin palustris (marsh arrow-grass)

Typha × glauca (hybrid cattail)

Typha angustifolia (narrow-leaved cattail)

Typha latifolia (broad-leaved cattail)

Ulmus pumila (Siberian elm)

Verbascum thapsus ssp. thapsus (common mullein)

Zizia aurea (golden alexanders)




bird’s-foot trefoil

black-eyed susan

bottle gentian

Canada anemone

Canadian tick-trefoil

common evening primrose

common sneezeweed

crown vetch

dotted blazing star

four-flowered yellow loosestrife

golden alexanders

green milkweed

hairy false goldenaster



long-headed coneflower

Maximilian’s sunflower

narrow-leaved purple coneflower

New England aster

plumeless thistle

poke milkweed

prairie blazing star

prairie onion

purple prairie clover

red clover

sulphur cinquefoil

shrubby cinquefoil

silky aster

small white lady’s slipper

spotted Joe Pye weed

spotted water hemlock

stiff sunflower (ssp. subrhomboideus)

swamp milkweed

swamp thistle

tall cinquefoil

Virginia mountain mint

wild licorice







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