Colusa Grass

Colusa GrassScientific Name: Gratiola heterosepala

Status: State-listed as endangered; California Native Plant Society List 1B.2

Distribution: Boggs Lake hedge-hyssop is found in six separate vernal pool regions, with most occurrences in the Modoc Plateau. Its range includes the inner north coast ranges, the Sacramento Valley, the Sierra Nevada Foothills, and Oregon. Boggs Lake hedge-hyssop is not found in the Natomas Basin; however, potential habitat exists along the eastern edge of the basin. The closest known occurrence is in Rio Linda, which is two miles east of the basin.

Habitat Requirements: Boggs Lake hedge-hyssop habitat includes clay soils of vernal pools and wet margins of freshwater lakes, stock ponds, borrow pits, marshes, and swamps at depths ranging from 2 to 28 inches. Its elevational range is 30″“7,800 feet (10″“2,400 meters), and it is associated with volcanic, basin rim, and high terrace landforms.

Demography: Boggs Lake hedge-hyssop is a small annual herb in the snapdragon family (Scrophulariaceae) that blooms April through August. The seedbank seems to be substantial, and population size varies widely from year to year. Boggs Lake hedge-hyssop is self-pollinating, and it is often found growing in association with smooth goldfields (Lasthenia glaberrima) and Douglas’ mesamint (Pogogyne douglasii). Higher elevation populations are associated with black oak (Quercus kelloggii) and foothill pine (Pinus sabiniana).

© Natomas Basin Habitat Conservation Plan & the Metro Air Park Habitat Conservation Plan