Slender Orcutt Grass

Slender Orcutt grass is found throughout the Modoc Plateau and Sacramento Valley in Modoc, Siskiyou, Shasta, Lassen, Plumas, Butte, Tehama, Lake and Sacramento Counties. Slender Orcutt grass only grows in vernal pools on Northern Volcanic Ashflows and Northern Volcanic Mudflows soils. The plants grow from 90 to 5,671 feet in elevation and may grow in grassland, oak woodland or conifer forest habitats. Slender Orcutt grass is known from about 100 locations, of which about six no longer exist. Thirty-one locations where the plant is thought to grow are on private land, and about 61 are on local, state, or federal lands. Slender Orcutt grass has been successfully introduced to new locations and is known from some areas that have been modified from the original vernal pool landscape to creek flood plains, stock ponds and borrow pits. 

Slender Orcutt grass looks different during each of its life stages. Plants in the aquatic phase are small and the stems lie flat or are supported by the water. Leaves that form during the aquatic life stage are cylindrical and clustered into a small rosette. As vernal pools dry, slender Orcutt grass plants become terrestrial. In its terrestrial stage, slender Orcutt grass grows 2 to 8 inches tall. Unlike most grasses, slender Orcutt stems are filled pith, which is a soft and spongy center found in many flowering plants. Each plant usually has one to a few stems that begin branching about halfway with the spikelets that support the florets. The cylindrical leaves of the aquatic life stage transform into flattened blades and are distributed along the stem during the terrestrial life stage. The stems and leaves are covered with small “hairs” that secrete a sticky substance. The stickiness increases as the plant matures and likely helps repel herbivores. Like other Orcutt grasses, the leaves lack a ligule (a small, outgrowth found at the junction of leaf and leafstalk on some grasses).

Slender Orcutt grass is an annual plant with three distinct life stages. Each rainy season, seeds from previous years sprouts and begin to grow underwater between November and January as the rains fill vernal pools. During the aquatic stage, slender Orcutt grass can be very difficult to find. As the pools dry, plants enter their terrestrial life stage. At this time, the grass can be seen within the vernal pool bottom through September. The grass blooms in the terrestrial life stage in May in the Sacramento Valley and June to July in the Modoc Plateau. The grass is thought to be wind pollinated like other Orcutt grasses for seed development. The seeds usually form after pollination in May through September and fall close to the plant upon maturity. Plants die after the seeds mature, and seeds do not travel far from the parent plant. Seeds are the final life stage of slender Orcutt grass, and the seeds may remain dormant in the soil for several years until there is enough water in the vernal pools for the seeds to sprout.