Willamette navarretia – State Wildlife Action Plan

Willamette navarretia is an annual plant that reaches 3-16 cm tall and wide with the primary head at the tip of the main stem and generally with 1-20 smaller heads at the tips of ascending lateral branches. The stems and branches are puberulent and green to reddish brown. The lower leaves are opposite or alternate with linear segments, glabrous to puberulent, and range in size from 10-50 mm long with up to 13 entire or branched lobes. The upper leaves are 10-22 mm long, alternate, and acerose with a puberulent rachis 4-10 mm long. The heads of N. willamettensis are 12-25 mm wide with 3-50 subsessile flowers. The calyx is 6.3-8.0 mm long with a membranous tube that is glabrous to gland-dotted or rarely puberulent between ribs and 2.3-3.5 mm long with 3-4 celled unbranched trichomes at the orifice and along the ribs. The 5 lobes on the calyx are glabrous and acerose with the two longest lobes 3.0-4.5 mm and often 2-3 pronged with the three shorter lobes 2.2-3.2 mm and simple. The corolla is funnelform and pink to lavender in color, 4.7-6.5 mm long and exceeding the shortest but not longest calyx lobes. The capsules are 2.3-3.0 mm long, membranous, and remain in the dried heads until they rupture with autumn rains as seed coat fibers imbibe water and expand. There are 2-6 brown ovoid-angular seeds that are 1.3-2.0 mm long, reticulate-pitted, and mucilaginous when wet.

Overview

Species Common Name Willamette navarretia
Species Scientific Name Navarretia willamettensis
Federal Listing Status Species of Concern
State Listing Status Endangered

Ecoregions

Willamette Valley

The Willamette Valley ecoregion is bounded on the west by the Coast Range and on the east by the Cascade Range. This long mostly level alluvial plain has some scattered areas of low basalt, and contrasts with productive farmland and large urban areas. It has the fastest-growing human population in the state resulting in challenges due to land-use changes.

Special needs

Willamette navarretia grows in seasonally wet meadows or prairies and vernal pools of the southern Willamette Valley. Occurs in habitats that are wet in the spring and dry in the late summer.

Limiting factors

Species range is severely restricted. Threatened by habitat conversion to agriculture, development, and habitat degradation. Without control efforts, invasive exotic plants pose a major threat. Species is ranked as highly vulnerable to climate change, particularly alterations to temperature and hydrological regimes.

Data gaps

Develop propagation and transplanting protocols. Document population status and trends.

Conservation actions

Continue seed production efforts. Manage sites to reduce invasive species. Monitor existing populations. Collect and bank seed as insurance against local extirpation or extinction and to use in ex-situ research. Conduct ex-situ seed/plug production for introduction and augmentation efforts.

Key reference or plan

Marshall, DA, and J Brown. 2023. 2023 listing status assessment for Navarretia willamettensis (Willamette navarretia). Oregon Department of Agriculture, Salem, Oregon.