Sidalcea nelsoniana - Piper
Nelson's Sidalcea
Other English Common Names: Nelson's Checker-Mallow, Nelson's Checkerbloom
Other Common Names: Nelson's checkerbloom
Taxonomic Status: Accepted
Related ITIS Name(s): Sidalcea nelsoniana Piper (TSN 21890)
Unique Identifier: ELEMENT_GLOBAL.2.135057
Element Code: PDMAL110H0
Informal Taxonomy: Plants, Vascular - Flowering Plants - Mallow Family
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Malvales Malvaceae Sidalcea
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Concept Reference
Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Sidalcea nelsoniana
Conservation Status

NatureServe Status

Global Status: G2G3
Global Status Last Reviewed: 29Jul2016
Global Status Last Changed: 08Feb1991
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G2 - Imperiled
Reasons: A regional endemic. Most occurrences are in the Willamette Valley of Oregon.  It is also known from the Coast Range in Oregon and two populations in southwest Washington. The moist, open habitats preferred by this species have been severely reduced from historical levels (especially the Willamette Valley) due to widespread agricultural and urban development. Approximately ninety occurrences remain, many of which are small. However, propagation and reintroduction efforts have had some success. Threats to this species are significant, particularly in the Willamette Valley, and include continuing agricultural and urban development; encroachment by woody plants in the absence of natural disturbance processes; competition with aggressive exotic plants; herbicide application, ditching, and other road maintenance practices; and pre-dispersal seed predation by weevils. Habitat degradation is thought to be a particular problem for population recruitment from seedlings and colonization of new sites. Plant numbers are expected to decline in the absence of active management.
Nation: United States
National Status: N2

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Oregon (S2), Washington (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LT: Listed threatened (12Feb1993)
U.S. Fish & Wildlife Service Lead Region: R1 - Pacific

NatureServe Global Conservation Status Factors

Range Extent Comments: Most sites occur in the Willamette Valley of Oregon, from southern Benton County northward through the central and western Willamette Valley to central Washington County, Oregon (USFWS 2010). Also found at several higher elevation meadows in the northern Coast Range of Oregon that flank the western Willamette Valley in Yamhill, Washington, Tillamook, counties, Oregon (USFWS 2010). Two other populations are known from the Puget Trough of adjacent southwest Washington, in Cowlitz and Lewis counties, Washington (Camp and Gamon 2011).

Area of Occupancy: 26-125 4-km2 grid cells
Area of Occupancy Comments: Area of Occupancy was calculated to be approximately 83 4-sq km grid cells (including occurrences with transplants, but excluding historical and extirpated occurrences) (NatureServe Network Database as of March 2016).  

Number of Occurrences: 81 - 300
Number of Occurrences Comments: 90 occurrences are currently believed extant, 88 in Oregon and 2 in Washington (NatureServe Network Database as of March 2016).  Of the 88 Oregon occurrences, approximately 10 include transplants.  In Oregon, an additional 10 occurrences are ranked as historical/unknown, and a further 4 are believed extirpated (NatureServe Network Database as of March 2016).  

Population Size Comments: Many known occurrences contain few plants. Based on occurrence data, total population size appears to be approximately 20,000 - 35,000 individuals (NatureServe Network Database as of March 2016).  Guerrant (2001) estimated a total of around 26,500 individuals as of 1997; since then, an additional 25 occurrences have been documented, but many of these are small.

Number of Occurrences with Good Viability/Integrity: Some (13-40)
Viability/Integrity Comments: Eight occurrences are believed to have excellent viability and one to have excellent or good viability; included among these are occurrences in William Finley National Wildlife Refuge and the Walker Flat ACEC/Nestucca River State Scenic Waterway, which are among the few sites remaining for this species that are not "heavily impacted by human presence" (Guerrant 2001). Another ten occurrences are believed to have good viability (NatureServe Network Database as of March 2016).  All occurrences with excellent or good viability rankings are in Oregon, as the two Washington populations are both in fairly heavily-disturbed habitat.

Overall Threat Impact: Very high - high
Overall Threat Impact Comments: Threatened by urban and agricultural development, ecological succession that results in shrub and tree encroachment of open prairie habitats, competition with invasive weeds including a dense thatch layer of non-native grasses, pre-dispersal seed predation by weevils, interspecific hybridization with other Sidalcea species, mowing, plowing, stream alteration, recreation, fire suppression, and roadside herbicide application (USFWS 2010; Camp and Gamon 2011).

(1) Habitat destruction due to agricultural, residential, and urban development continues to threaten many populations, particularly those on private lands in the Willamette Valley; these threats are generally less severe in the Coast Range, as many occupied meadows there are relatively isolated from development. However, one significant land use threat in the Coast Range is the potential construction of a dam and reservoir by McMinnville Water and Light on Walker Creek, which would inundate a very large population found in a natural habitat, features which are rare among known occurrences. This project has been contested since the mid-1980s; currently, the Nestucca River is listed under the Oregon Scenic Waterway System and a portion of the population is managed as an Area of Critical Environmental Concern by the BLM, but these protections are not considered permanent (e.g. the Oregon legislature can remove the Scenic Waterway designation). (2) Habitat quality is also highly threatened by successional encroachment of trees and shrubs, primarily resulting from suppression of natural disturbance regimes such as periodic flooding and fires. Encroachment occurs in both the Willamette Valley and Coast Range, but appears to be more problematic in the Willamette Valley since Coast Range meadows are to some degree kept open by elk and deer browsing and occasional floods and forest fires, and invading woody plant species appear to be less pervasive in the Coast Range than in the Willamette Valley. (3) Competition with aggressive exotic plant species is also a significant threat, again particularly in the Willamette Valley. Although mature, established plants appear to compete effectively with aggressive exotics such as Canada thistle, the dense stands and thatch produced by the exotic species that dominate much S. nelsoniana habitat in the Willamette Valley are thought to significantly limit seedling recruitment at occupied sites, as well as colonization of additional, potentially suitable sites. Although some exotic species have invaded preferred mountain meadow habitat in the Coast Range, native plants generally are still well-represented at those sites, and the habitats are less fragmented with more stable composition. (4) Particularly on lands without a conservation management mandate (including roadsides and agricultural field edges), populations also often experience collateral impacts from management practices such as herbicide spraying, inappropriately-timed mowing, road widening and maintenance, deposition of debris, plowing, ditching, and stream channel alteration. (5) In the Coast Range, populations within or adjacent to logged areas are potentially threatened by drift from the herbicides often sprayed on these site just prior to reforestation. (6) The habitat of several Coast Range populations is also disturbed by recreational use by motorcyclists. (7) Particularly in the Willamette Valley, populations are also subject to significant pre-dispersal seed predation by a weevil (Macrohoptus sidalceae); for example, Gisler and Meinke (1997) found that production of undamaged seeds averaged just 14.6% of total ovules across eight predated populations they studied. Predation can be reduced by applying an insecticide to inflorescences early in the flowering season, but since the weevil is native, specific to Pacific Northwest Sidalcea, and itself hosts an unidentified species of parasitic wasp, this strategy may not be attractive from an overall biodiversity conservation perspective (Gisler 2004). (8) Finally, the potential for genetic swamping via hybridization with other Sidalcea species needs careful management. Currently, various pre- and post-mating barriers discourage such hybridization, but these barriers could be overcome if species are planted beyond their current distributions or if different species are grown in close proximity for cultivation purposes. The potential for hybridization with S. cusickii is a particular concern, as this species is fully interfertile with S. nelsoniana; the only current reproductive isolation is by geographic separation of ranges (Gisler 2004).  

Short-term Trend: Decline of <50% to Relatively Stable
Short-term Trend Comments: Since 1990, three occurrences are known to have been extirpated by construction at an airport, bulldozing for a housing development, and raising of the water level in a reservoir, respectively. On the other hand, recent introduction and reintroduction efforts at several sites appear to have resulted in established populations. At the Finley National Wildlife Refuge, one of the few remaining places in the Willamette Valley where this species occurs in a relatively natural habitat, plant numbers are declining, likely due to habitat degradation of the sort widespread throughout the Valley (i.e. encroachment of woody plants and competition from aggressive exotic species) (M. B. Naughton, personal observation cited in Wilson 2004). Guerrant (2001) suggests that, overall, "population numbers are declining."

Long-term Trend: Decline of 10-80%
Long-term Trend Comments: Prior to European settlement, the moist, open habitats preferred by this species were likely maintained by natural wildfires, fires set by Native Americans, and sporadic flooding. These landscape processes have been dramatically suppressed since that time, resulting in successional woody overgrowth of many formerly open sites. In addition, livestock grazing, agricultural and urban land conversion, and stream channel alterations have greatly reduced the quantity and quality of this species' preferred habitat, especially in the Willamette Valley; Bartels and Wilson (2003) state that land use changes over the past 150 years have altered or destroyed more than 99% of Willamette Valley wetland habitats. Although there is no direct evidence of this species' abundance prior to European settlement, the vast declines in its preferred habitat strongly suggest that plants historically occurred more extensively throughout native Willamette Valley grasslands. In the Coast Range, habitat decline since European settlement does not appear to have been as severe, although habitat quality impacts (e.g. aggressive introduced species) are still apparent. Interestingly, some sources have suggested that this species may have been more recently introduced into Coast Range mountain meadows via livestock feed originating in the Willamette Valley (CH2M Hill 1986 cited in USFWS 1998).

Intrinsic Vulnerability Comments: The species' high susceptibility to pre-dispersal seed predation by weevils may eventually lead to recruitment problems, particularly in small populations already subject to other stresses such as competition with dense stands of invasive species. However, the ease of propagating this species by both seeds and rhizomes (Gisler 2004) suggests that its rarity may be more related to the significant destruction and degradation of its habitat rather than to any intrinsic vulnerability of the plants themselves.

Other NatureServe Conservation Status Information

Global Range: Most sites occur in the Willamette Valley of Oregon, from southern Benton County northward through the central and western Willamette Valley to central Washington County, Oregon (USFWS 2010). Also found at several higher elevation meadows in the northern Coast Range of Oregon that flank the western Willamette Valley in Yamhill, Washington, Tillamook, counties, Oregon (USFWS 2010). Two other populations are known from the Puget Trough of adjacent southwest Washington, in Cowlitz and Lewis counties, Washington (Camp and Gamon 2011).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States OR, WA

Range Map
No map available.

U.S. Distribution by County Help
State County Name (FIPS Code)
OR Benton (41003), Clackamas (41005)*, Clatsop (41007), Columbia (41009), Linn (41043), Marion (41047), Polk (41053), Tillamook (41057), Washington (41067), Yamhill (41071)
WA Cowlitz (53015), Lewis (53041)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
17 Lower Columbia-Clatskanie (17080003)+, Upper Willamette (17090003)+, North Santiam (17090005)+, South Santiam (17090006)+, Middle Willamette (17090007)+, Yamhill (17090008)+, Molalla-Pudding (17090009)+*, Tualatin (17090010)+, Clackamas (17090011)+*, Upper Chehalis (17100103)+, Nehalem (17100202)+, Wilson-Trusk-Nestuccu (17100203)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: A perennial herb with densely clustered stems, up to 1 m tall. Leaves are increasingly deeply cleft towards the top of the stems. Magenta flowers in a spike-like cluster bloom from late May through mid July.
General Description: An herbaceous perennial with palmately lobed basal leaves, upper stem leaves deeply divided, and stems variably covered with simple hairs; plants have short, thick, twisted underground stems as well as a system of fine roots extending from a stout taproot. Plants produce numerous flowering stems 60 to 100 cm tall, each with 30 to 100 pink flowers on very short stalks. Mature plants produce either exclusively female flowers, or flowers with both male and female parts. Female flowers are generally smaller and lack functioning pollen sacs at the ends of the stamens. The stamens are fused at the base to form a tube around the style. Fruits consist of a ring of 7 to 9 single-seeded, beaked segments (like segments of an orange), which separate at maturity (USFWS 1998).
Technical Description: Erect perennial from a stout taproot, plants with either bisexual or female flowers (gynodioecious breeding system). Stems 60-100 cm tall, somewhat glaucous, glabrous to pubescent with short, appressed, simple hairs. Leaf blades orbicular, extremely variable in lobing, basal leaves shallowly 5-7-lobed, upper ones deeply parted, glabrous above, sparsely hairy with simple hairs beneath, 5-10 cm broad, the lower ones ca. seven lobed, the lobes toothed, upper leaves increasingly deeply cleft. Inflorescence a many-flowered, elongate, open, spikelike raceme; pedicels ca. 3 mm long. Flowers bisexual or female, the bisexual ones larger than the females; calyx nearly smooth, 4-6 mm long, purplish tinged, glabrous or pubescent with stellate hairs; petals rose-colored, 5-15 mm long; stamens united in a tube surrounding style. Fruits schizocarps; carpels ca. 3 mm long (Meinke 1982, Oregon Flora Project 2006).
Diagnostic Characteristics: Sidalcea nelsoniana can be distinguished from S. virgata by its smaller, more tightly clustered pink flowers (vs. distinctively deep pink to rose-colored flowers), its presence in wetland habitats (vs. drier, more upland sites), its nearly smooth calyx (vs. sepals uniformly finely stellate), its simple stem hairs (vs. forked-branched stem hairs), its taller height, and its later flowering time. It can be distinguished from S. campestris by its smaller, pink flowers (vs. larger white to pale pink flowers) and its shorter height. It can be distinguished from S. cusickii by its simple stem hairs (vs. generally forked stem hairs), its narrower calyx lobes, and its less prominently-veined petals. It can be distinguished from S. hirtipes by its shorter and less hairy calyx, its shorter petals, its stem with fewer, shorter hairs, and its lack of occurrence in coastal habitats. It can be distinguished from S. hendersonii by its shorter calyx, its reduced amount of pubescence, and its lack of occurrence on tidal flats (USFWS 1998, Washington NHP 1999, Oregon Flora project 2006).
Reproduction Comments: This species has a gynodioecious breeding system, whereby individuals can either be hermaphroditic (bearing flowers with both male and female sex organs) or female (bearing male-sterile flowers). Because female flowers do not produce pollen, they require insect-mediated outcrossed pollen in order to produce seeds. Although hermaphroditic flowers produce pollen, within-flower self-fertilization is discouraged by protandry, whereby pollen dehisces 2-3 days prior to stigma emergence and receptivity. However, self-fertilization can still occur in hermaphroditic plants through pollen transfer between different flowers on the same inflorescence or between adjacent ramets of the same genet (Gisler 2004). Note that this species can also reproduce vegetatively via rhizomes, but rhizomes are more likely to reproduce vegetatively through breaking, with the broken-off part being moved away from the parent plant, than they are by sending out long rhizomes that give rise to new plants. It is currently unknown to what extent population maintenance in this species is dependent upon asexual expansion versus sexual reproduction (Gisler 2004).
Palustrine Habitat(s): HERBACEOUS WETLAND, Riparian
Terrestrial Habitat(s): Forest - Conifer, Forest Edge, Forest/Woodland, Grassland/herbaceous, Old field, Savanna, Woodland - Hardwood
Habitat Comments: Generally found in soils that become saturated during the rainy season, with plants frequently becoming inundated for several weeks or longer. Other than this, soils are relatively variable, ranging from gravelly, well drained loams, to poorly drained, hydric clay soils. Currently, plants are found in both relatively undisturbed sites and in sites with greater disturbance; however, it is unclear to what degree seedling recruitment occurs in weedy sites, and how long populations can persist under such conditions after mature plants with large, established root systems die. Although sites are generally moist and open, the character of the habitat differs somewhat between the Willamette Valley and Coast Range. In the Willamette Valley, sites occur within a mosaic of urban and agricultural areas from 45-200 m elevation. Sites are usually open or at the edge between open areas and deciduous woodlands, although populations occasionally occur in the understory of woodlands or among woody shrubs. However, it is uncertain how long plants can persist under closed canopies, and it is thought that the few populations currently found in these conditions likely colonized the sites at earlier successional stages (Gisler 2004). Habitats are often native prairie remnants, and include old cemeteries, roadsides, fencerows, edges of plowed fields adjacent to wooded areas, margins of streams, sloughs, ditches, drainage swales, hay fields, and fallow fields. Most known sites have been densely colonized by invasive weeds, especially introduced forage grasses. Associated species in the Willamette Valley include tall fescue (Festuca arundinacea), rose (Rosa spp.), common rush (Juncus effusus), Canada thistle (Cirsium arvense), common St. John's-wort (Hypericum perforatum), blackberry (Rubus spp.), sedge (Carex spp.), Timothy (Phleum pratense), velvet grass (Holcus lanatus), yarrow (Achillea millefolium), vetch (Vicia spp.), Western spiraea (Spirea douglasii), bird's-foot trefoil (Lotus corniculatus), ox-eyed daisy (Chrysanthemum leucanthemum), colonial bent-grass (Agrostis tenuis), meadow foxtail (Alopecurus pratensis), reed canary-grass (Phalaris arundinacea), Douglas' hawthorn (Crataegus douglasii), wild carrot (Daucus carota), large-leaved avens (Geum macrophyllum), geranium (Geranium spp.), and Oregon ash (Fraxinus latifolia). In the Coast Range, populations primarily occupy open, grassy sites within a larger matrix of coniferous forest from 490-610 m elevation. Habitats include open wet to dry meadows, intermittent stream channels, and margins of coniferous forests. These areas generally support higher components of native vegetation than Willamette Valley sites. Associated species in the Coast Range include tansy ragwort (Senecio jacobaea), spear-head senecio (S. triangularis), strawberry (Fragaria virginiana), velvet grass (Holcus lanatus), timothy (Phleum pratense), rush (Juncus spp.), sedge (Carex spp.), and yarrow (Achillea millefolium).  (Camp and Gamon 2011; Oregon Flora Project 2006; USFWS 2012)
Economic Attributes Not yet assessed
Management Summary
Stewardship Overview: Continue to monitor known populations. Study and implement threat reduction. At sites where natural disturbance processes no longer serve to prevent encroachment by woody species, active management is necessary to keep habitats in the open state preferred by Sidalcea nelsoniana. Active management may also be required to allow S. nelsoniana recruitment from seeds at sites with significant invasion by exotic species and associated thick thatch layers. The best methods by which to achieve optimal open habitat for this species are still a matter of active research. The U.S. Fish and Wildlife Service (1993) reported that "plants found in areas that have been burned to benefit geese are more robust than those plants in non-burned locations," suggesting that prescribed burning could be an effective management tool. However, Wilson (2004) found that experimental prescribed burning treatments did not provide short-term benefits to S. nelsoniana plants, although he allowed that benefits may become evident in the longer term. Wilson found that burning appeared both to directly damage S. nelsoniana plants as well as to stimulate growth of herbaceous competitors, particularly at wetter sites. Additional study of prescribed burning's effects on this species may reveal the reason for the apparently conflicting results of these two reports. Wilson (2004) also experimented with mowing as a management technique, but there was little convincing evidence of short-term benefit to S. nelsoniana from this treatment either. However, mowing did provide some benefit under some of the experimental conditions and did not directly damage S. nelsoniana plants to the same extent as burning. It is possible that appropriately-timed mowing in combination with other strategies, such as hand-removal of herbaceous competitors, may prove to be useful for management. Managing to increase the duration of flooding at S. nelsoniana sites has also been considered. However, Bartels and Wilson (2003) found that plants flooded past mid-spring (the historical end of the flooding season in the Willamette Valley) exhibited poor survival and vigor, suggesting that managers should not flood sites past this time.
Population/Occurrence Delineation Not yet assessed
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 29Jul2016
NatureServe Conservation Status Factors Author: Oregon Natural Heritage Program, rev. K. Gravuer (2008), rev. A. Tomaino (2016)
Management Information Edition Date: 01Aug2016
Management Information Edition Author: Gravuer, K., rev. A. Tomaino (2016)

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

  • Bartels, M. R. and M. V. Wilson. 2003. Flood tolerance of the threatened Sildalcea nelsoniana (Malvaceae). Madroņo 50(4): 265-270.

  • CH2M Hill. 1986. Studies of Sidalcea nelsoniana. Submitted to US Fish and Wildlife Service and US Bureau of Land Management. Submitted by City of McMinnville Dept. of Water and Light.

  • CH2M Hill. 1987. Studies of Sidalcea nelsoniana. Submitted to US Fish and Wildlife Service and US Bureau of Land Management. Submitted by City of McMinnville Dept. of Water and Light.

  • CH2M Hill. 1989. Studies of Sidalcea nelsoniana. Submitted to USFWS and BLM by McMinnville Water and Light.

  • CH2M Hill. 1990. Preliminary engineering report, Tenmile Water Supply project for Coos County Urban Renewal Agency, Coos Bay-North Bend Water Board. CH2M Hill, Portland, OR. Unpublished report on file at Oregon Natural Heritage Data Base.

  • CH2M Hill. 1991. Studies of Sidalcea nelsoniana. Submitted to US Fish and Wildlife Service and US Bureau of Land Management by City of McMinnville Water and Light Dept.

  • Camp, P., and J.G. Gamon, eds. 2011. Field Guide to the Rare Plants of Washington. Washington Natural Heritage Program and Washington State Department of Natural Resources. University of Washington Press, Seattle. 408 pp.

  • Flora of North America Editorial Committee. 2015. Flora of North America North of Mexico. Vol. 6. Magnoliophyta: Cucurbitaceae to Droserceae. Oxford University Press, New York. 496 pp + xxiv.

  • Gilkey, H.M. 1961. Handbook of Northwest flowering plants. 2nd edition revised. Binfords and Mort, Portland, Oregon. 390 pp.

  • Gisler, S. D. and R. J. Meinke. 1997. Reproductive attrition by pre-dispersal seed predation in Sidalcea nelsoniana (Malvaceae): Implications for the recovery of a threatened species. Pgs. 56-61 in Kaye, T.N., A. Liston, R.M. Love, D.L. Luoma, R.J. Meinke, and M.V. Wilson, eds. Conservation and management of native plants and fungi: Proceedings of an Oregon conference on the conservation and management of native vascular plants, bryophytes, and fungi. Native Plant Society of Oregon, Corvallis.

  • Gisler, S.D. 2004. Developing biogeographically based population introduction protocols for at-risk Willamette Valley plant species. Report to US Fish and Wildlife Service, Portland, Oregon. Native Plant Conservation Program, Oregon Department of Agriculture, Salem, Oregon.

  • Glad, J.B., R. Mishaga, and R.R. Halse. 1987. Habitat characteristics of Sidalcea nelsoniana Piper (Malvaceae) at Walker Flat, Yamhill County, Oregon. Northwest Science 61:257-263.

  • Guerrant, E. 2001. National Collection Plant Profile: Sidalcea nelsoniana, Center for Plant Conservation. Online. Available: (Accessed 2008).

  • Halse, R.R., B.A. Rottink, and R. Mishaga. 1989. Studies in Sidalcea taxonomy. Northwest Science, Vol. 63, No. 4:154-161.

  • Hitchcock, C.L., and A. Cronquist. 1973. Flora of the Pacific Northwest: An Illustrated Manual. University of Washington Press, Seattle, Washington. 730 pp.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Meinke, R.J. 1982. Threatened and Endangered Vascular Plants of Oregon: An Illustrated Guide. U.S. Fish and Wildlife Service, Region 1, Portland, Oregon. 326 pp.

  • Oregon Flora Project. 2006. Fact Sheet for Sidalcea nelsoniana. Rare Plant Guide. []

  • Peck, M.E. 1961. A manual of the higher plants of Oregon. 2nd edition. Binsford & Mort, Portland, Oregon. 936 pp.

  • U. S. Fish and Wildlife Service (USFWS). 1993. Endangered and Threatened Wildlife and Plants; Determination of Threatened Status for the Plant "Sidalcea nelsoniana" (Nelson's Checker-mallow). Federal Register 58(28): 8235-8243.

  • U.S. Fish and Wildlife Service (USFWS). 1998. Recovery Plan for the Threatened Nelson's Checker-mallow (Sidalcea nelsoniana). Portland, Oregon. 61 pp.

  • U.S. Fish and Wildlife Service (USFWS). 2010. Recovery Plan for the Prairie Species of Western Oregon and Southwestern Washington. U.S. Fish and Wildlife Service, Portland, Oregon. xi + 241 pp. [

  • Washington Natural Heritage Program (WNHP) and Bureau of Land Management (BLM). 1999. Field guide to selected rare vascular plants of Washington. Washington Department of Natural Resources.

  • Wilson, M. V. 2004. The analysis of management strategies to restore and enhance Nelson's checker-mallow (Sidalcea nelsoniana) habitat at William L. Finley National Wildlife Refuge. Response to two years of restoration techniques in an existing Sidalcea nelsoniana habitat: Final report. Submitted to U.S. Fish and Wildlife Service (Order Nos. 1448-13420-97-M303, 1448-13420-98-M279, 101819-M584), 7 May 2004. Online. Available:

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