Thermopsis robusta
| Thermopsis robusta | |
|---|---|
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Fabales |
| Family: | Fabaceae |
| Subfamily: | Faboideae |
| Genus: | Thermopsis |
| Species: | T. robusta |
| Binomial name | |
| Thermopsis robusta | |
Thermopsis robusta, commonly known as the robust false lupine or showy golden-banner, is a rare species of flowering plant in the legume family, Fabaceae. It is a perennial herb endemic to northern California and southwestern Oregon in the United States. It grows in open forest habitats, meadows, ridgelines, roadsides, and areas of shale or serpentine soils.[2][1]
The species is characterized by its tall, stout stems, densely hairy leaves, long flower clusters, and curved, densely hairy fruits.[2]
Description
Thermopsis robusta is a perennial herb. The plant ranges from green to grayish in appearance because of its dense covering of hairs. The stems are erect and stout, with few or no branches arising near the base.[2]
The leaves are divided into three leaflets, as is typical of the genus Thermopsis. The leaflets are densely covered with long, soft, wavy hairs. Each leaflet has approximately 18 to 24 pairs of lateral veins.[2]
The inflorescence is an elongated cluster. Flowers are generally arranged in groups of three to five at each node of the inflorescence.[2]
The flowers are yellow and pea-like, with the characteristic banner, wing, and keel petals of the family Fabaceae. The fruit is a curved, spreading pod that is densely covered with hairs.[2]
Flowering generally occurs from May through June.[2]
Taxonomy
Thermopsis robusta was formally described by American botanist Thomas Jefferson Howell in 1893. The name was published in volume 1 of Erythea, a botanical journal devoted to plants of western North America.[3]
The name is cited as:
- Thermopsis robusta Howell, Erythea 1: 109. 1893.[3]
The original type material was collected in California.[3] The specific epithet robusta is Latin for “robust” or “stout” and refers to the plant's strong, upright growth.
Distribution
Thermopsis robusta is endemic to a limited region of northwestern California and southwestern Oregon.[1]
In California, it occurs in Del Norte, Humboldt, Mendocino, Siskiyou, and Trinity counties. In Oregon, it is known from Curry and Josephine counties.[1]
Habitat and ecology
Thermopsis robusta grows in open areas within coniferous and mixed evergreen forests. It occurs along ridgelines and roadsides, in meadows, forest openings, and transitional areas associated with serpentine substrates.[1]
In California, it has been reported from shale and serpentine soils at elevations of approximately 150–1,500 m (490–4,920 ft).[2]
The species appears to function as an early-successional colonizer. It is often found in places that have experienced periodic disturbance, including recently opened forest sites and roadsides. Suitable habitat may shift over time as vegetation develops following disturbance.[1]
Historically, natural fire may have helped maintain the open habitat required by the species. Fire suppression can allow denser forest or shrub cover to develop, reducing suitable conditions.[1]
Conservation
NatureServe assigns Thermopsis robusta a global conservation rank of G2, or imperiled. It is also ranked N2 in the United States, S2 in California, and S1, or critically imperiled, in Oregon. It has no status under the United States Endangered Species Act.[1]
The global rank was last formally reviewed on 12 June 2000 and is identified by NatureServe as needing review. However, NatureServe's supporting conservation factors were revised in 2023 using more recent distribution and occurrence information.[1]
NatureServe reports approximately 83 occurrences in California and three in Oregon when populations are separated using a distance of 1 km (0.62 mi). Only some occurrences are considered to have good ecological integrity or viability.[1]
Nearly half of known occurrences are found along roadsides. These populations may benefit temporarily from open conditions created by road construction or maintenance, but they are also vulnerable to grading, mowing, herbicide use, roadside expansion, and vehicle traffic.[1]
Other threats include logging, off-road vehicle use, fire suppression, invasive plants, and competition from more aggressive vegetation. Around 45 percent of known occurrences may be affected by logging. Invasive Scotch broom and French broom may compete with the species in disturbed habitats.[1]
NatureServe estimates a long-term decline of 10 to 30 percent. One occurrence is known to have been extirpated, and 22 others had not been observed for more than 20 years at the time of the assessment. The estimated short-term decline is 30 to 50 percent, based partly on the low viability of nearly half of known occurrences.[1]
Many populations occur on federal lands, including the Klamath National Forest, Rogue River–Siskiyou National Forest, and Six Rivers National Forest.[1]
References
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 "Thermopsis robusta". NatureServe Explorer. NatureServe. Retrieved 16 July 2026.
- 1 2 3 4 5 6 7 8 Wilken, Dieter H. (2012). "Thermopsis robusta". Jepson eFlora. Jepson Flora Project, University of California, Berkeley. Retrieved 16 July 2026.
- 1 2 3 "Thermopsis robusta Howell". International Plant Names Index. Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Herbarium. Retrieved 16 July 2026.