Eriogonum umbellatum
Eriogonum umbellatum is a species of wild buckwheat known by the common name sulphurflower buckwheat, or simply sulphur flower. It is native to western North America from California to Colorado to central Canada, where it is abundant and found in many habitats. This is an extremely variable plant and hard to identify because individuals can look very different from one another. Also, there are a great many varieties. It may be a perennial herb forming a small clump with flowers to 10 centimeters tall, or a sprawling shrub approaching two meters high and wide. The leaves are usually woolly and low on the plant, and the flowers come in many colors from white to bright yellow to purple. Native American groups utilized parts of this plant for a number of medicinal uses.
It is a popular larval host, feeding the bramble hairstreak, desert green hairstreak, lupine blue, Mormon metalmark, Rocky Mountain dotted blue, Sheridan's hairstreak, Sonoran metalmark, and western green hairstreak. Additionally, goats and domestic sheep feed on the plant.
Varieties of this species include, but are not limited to:
- E. u. var. argus - often nearly hairless leaves and bright yellow flowers; limited to the Klamath Mountains
- E. u. var. dichrocephalum - found throughout much of the western United States
- E. u. var. furcosum - a low shrub native to the Sierra Nevada
- E. u. var. glaberrimum - - a nearly hairless, white-flowered species
- E. u. var. humistratum - - a rare northern California endemic
- E. u. var. juniporinum - - an uncommon plant of eastern California and western Nevada
- E. u. var. subalpinum - - similar to Eriogonum eriogonum but has wider and more spoon-shaped leaves
- E. u. var. torreyanum - - known from fewer than 10 occurrences near the Donner Pass
- E. u. var. versicolor - bears pinkish-brown flowers with bright stripes
