Loess Hill Prairie

Last updated: June 14th, 2025 by Grant Fessler

Loess hill prairies are grassland communities which developed on thick loess (windblown silt) deposits, typically on south to west facing slopes of river bluffs (Illinois Department of Natural Resources 2023; NatureServe 2025). The soils are dry-mesic to dry and calcareous. The steep, exposed, windswept, and droughty landscape positions on which hill prairies occur are largely responsible for their maintenance, in addition to periodic fire and grazing activity in presettlement times (Evers 1955; NatureServe 2025). This prairie type is restricted to the Illinois and Mississippi River valleys in Illinois and is considered Globally Imperiled (G2) by NatureServe (2025). Loess hill prairies were once common in Illinois in presettlement times, but they have since become much diminished due to fire suppression, forest encroachment, and invasive species. We are fortunate in the Quad Cities Region to have at least two high-quality examples of this community in Rock Island County, Indian Bluff Hill Prairie Nature Preserve and Josua Lindahl Hill Prairies Nature Preserves. Undoubtedly, this community occurred in Henry, Mercer, and Whiteside counties prior to European colonization.

  • Loess hill prairie colored by the mid-Summer blooms of Amorpha canescens and Dalea purpurea.
  • Dry loess hill prairie in early summer with Amorpha canescens, Euphorbia corollata, and Schizachyrium scoparium. Rock Island Co., IL.
  • Lithospermum canescens aglow on a sunny May afternoon
  • Castilleja sessiliflora in bloom on a loess hill prairie
  • Carex richardsonii in flower
  • Carex inops ssp. heliophila in bloom

The vegetation of loess hill prairies is characterized by medium-height grasses and dry prairie forbs. Schizachyrium scoparium is typically dominant and accompanied by Andropogon gerardii, Bouteloua curtipendula, and Sorghastrum nutans. The native shrub Amorpha canescens is often important in high-quality examples. Matrix forbs include Anemone cylindrica, Asclepias verticillata, Brickellia eupatorioides, Dalea purpurea, Euphorbia corollata, Lithospermum canescens, Physalis virginiana, Sisyrinchium campestre, Solidago nemoralis, and Symphyotrichum oolentangiense. Characteristic species include Asclepias viridiflora, Carex richardsonii, Carex umbellata, Celastrus scandens, Cirsium hillii, Liatris cylindracea, Lobelia spicata, Oxalis violacea, Ruellia humilis, Scutellaria parvula, Solidago ptarmicoides, and Viola pedatifida. A unique feature of loess hill prairies is the presence of western prairie plains relicts. In Rock Island County, such species include Carex inops ssp. heliophila, Castilleja sessiliflora, and Onosmodium occidentale.

References


Evers, R. A. 1955. Hill prairies of Illinois. Bulletin of the Illinois Natural History Survey 26(5):367-446.

Illinois Department of Natural Resources. 2023. Illinois Natural Areas Inventory Standards and Guidelines (revised edition). Springfield, Illinois. 105 pp.

NatureServe. 2025. Schizachyrium scoparium – Sorghastrum nutans – Bouteloua curtipendula Loess Hill Grassland. NatureServe, Arlington, Virginia. https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.688071/Schizachyrium_scoparium_-Sorghastrum_nutans-_Bouteloua_curtipendula_Loess_Hill_Grassland