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Prairie Species Habitat Conservation Plan – Nelson’s Checkermallow

Sidalcea nelsoniana


Nelson’s checkermallow was listed as threatened under the federal Endangered Species Act in 1993. The species is also listed as threatened by the state of Oregon. A recovery plan for the species was finalized in 1998 (see more information), and critical habitat is likely to be designated in late 2006.


Nelson’s checkermallow is a perennial forb, and a member of the mallow family (Malvaceae). The species has pinkish-purplish flowers clustered at the end of 2-4 ft tall stems. Nelson’s checker-mallow reproduces both by seeds (typically mature in August) and vegetative rhizomes.

Nelson’s checkermallow (Sidalcea nelsoniana) can be easily confused with other checkermallow species. Dwarf checkermallow (Sidalcea virgata) and Meadow checkermallow (Sidalcea campestris) are common in the Willamette Valley, and can be found in similar habitat. Nelson’s checkermallow can best be differentiated from the other checkermallows during flowering; flowers of Nelson’s checkermallow are typically smaller and more tightly clustered than flowers of dwarf checkermallow, and dwarf checkermallow tends to occur in drier, more upland habitats than Nelson’s checkermallow. Meadow checkermallow flowers tend to be larger and paler pink than Nelson’s checkermallow flowers.

Range and Habitat

This species typically occurs in wet prairies of the Willamette Valley, the northern Coast Range and southwest Washington. It can also be found along roadsides, in wetlands, and along streams through meadows.


Remaining populations of Nelson’s checkermallow are at risk from:

  • Further habitat loss or fragmentation
  • Invasion of prairie habitats by non-native species
  • Encroachment of trees and shrubs into prairie habitats
  • Elimination of natural disturbance regimes
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