Nelson's checkermallow was federally listed as threatened without critical habitat in 1993 (U.S. Fish and Wildlife Service 1993). A recovery plan was published in 1998 (U.S. Fish and Wildlife Service 1998).

Description and Life History

Nelson's checkermallow is a perennial herb in the mallow family (Malvaceae). It has tall, lavender to deep pink flowers. The flowers are borne in clusters 50-150 cm (1.6-5 ft) tall at the end of short stalks. These clusters (inflorescences) are usually spike-like, elongate, and somewhat open. Plants have either perfect flowers (male and female) or pistillate flowers (female only). The plant can reproduce vegetatively, by rhizomes, and by seeds, which drop near the parent plant. Flowering can occur as early as mid-May and extend into September in the Willamette Valley, Oregon. Fruits have been observed as early as mid-June and as late as mid-October. Coast Range populations generally flower later and produce seed earlier, probably because of the shorter growing season.

Habitat

Within the Willamette Valley, Nelson's checkermallow most frequently occurs in Oregon ash (Fraxinus latifolia) swales and meadows with wet depressions, or along streams. The species also grows in wetlands within remnant prairie grasslands. Some populations occur along roadsides at stream crossings where non-native plants, such as reed canarygrass (Phalaris arundinacea), blackberry (Rubus spp.), and Queen Anne's lace (Daucus carota), are also present. Nelson's checkermallow primarily occurs in open areas with little or no shade and will not tolerate encroachment of woody species.

In the Willamette Valley, Nelson's checkermallow occurs on soils in the Wapto, Bashaw and Mcalpin Series (NRCS mapped soil unit STATSGO 81) and Malabon, Coburg and Salem Series (NRCS mapped soil unit STATSGO 91).

Reasons for Decline

Prior to European colonization of the Willamette Valley, naturally occurring fires and fires set by Native Americans maintained suitable Nelson's checkermallow habitat. Current fire suppression practices allow succession by introduced and native trees and shrubs; the trees may gradually invade habitat for Nelson's checkermallow. Remnant prairie patches in the Willamette Valley have been modified by livestock grazing, fire suppression, or agricultural land conversion. Stream channel alterations, such as straightening, splash dam installation, and rip-rapping cause accelerated drainage and reduce the amount of water that is diverted naturally into adjacent meadow areas. As a result, areas that would support Nelson's checkermallow are lost.

Range

The majority of sites where the species occurs is in the Willamette Valley of Oregon; the plant is also found at several sites in the Coast Range of Oregon and at two sites in the Puget Trough of southwestern Washington. Thus, the range of the plant extends from southern Benton County, Oregon, north to Cowlitz County, Washington, and from central Linn County, Oregon, west to the crest of the Coast Range. The species is known to occur in 62 patches within 5 relict population centers in Oregon, and at 2 sites in Washington.

References and Links

U.S. Fish and Wildlife Service. 1993. Determination of Threatened Status for the Plant Sidalcea nelsoniana (Nelson's Checker-mallow). Federal Register 58:8235-8243. https://ecos.fws.gov/docs/frdocs/1993/93-3353.pdf

U.S. Fish and Wildlife Service. 1998. Recovery Plan for the Threatened Nelson's Checker-mallow (Sidalcea nelsoniana). Portland, Oregon. 61 pp. http://ecos.fws.gov/docs/recovery_plans/1998/980930e.pdf