Orcuttia tenuis

5 toothed lemma is best and easiest field characteristic. The aromatic, sticky secretion is less reliable in higher elevation populations.

Vernal Pools with a very well developed soil profile. O. tenuis prefers clay soils which shrink and swell. As they dry, large cracks develop which allow seeds trapped deeply in the soil to float to the surface with the first inundation. Between 14 and 50 times as many seeds are in the soil as live plants, too deep to germinate. Habitat creation for this plant would probably not succeed because of its requirement for these well developed soils. Conversely, any activity which disturbs the soil profile will negatively effect O. tenuis. Vernal pools; Elevation: 200-1100 m (Jepson FloraProject 2017).

The genus Orcuttia forms a distinct group within the grass family with no apparent affinities to any other grasses, probably of very ancient origin. The plant is covered with a sticky secretion which may have several functions; repelling herbivores, assisting in dispersal by sticking seeds to fur, feathers and feet, and reducing water loss. At higher (cooler) occurrences, exudate is less obvious. Associates include coyote thistle (Eryngium vaseyi), spike rush (Eleocharis palustrus), downingia spp., Tehema navarretia (navarretia heteranda), hairy orcutt grass (Orcuttia pilosa) and Green's orcutt grass (Tuctoria greenei). Each occurrence can vary in size from a few square meters to several hectares containing a very large number of plants. Populations of several thousand individuals have been observed. The seeds require enough standing water to allow the growth of a fungus over the seed coat to break dormancy. In dry years the seeds remain dormant and can be viable for many years. Seedlings tolerate the anaerobic conditions of submersion. As the water temperature rises the seedlings produce two long, floating leaves that collect sunlight, CO2 and O2 for photosynthesis. As the plant grows above the water level new, shorter leaves appear. As the pool dries completely and the conditions become xeric the plant switches to a C-4 photosynthetic pathway and all resources are dedicated to flowering and seed set. The plant sets seed in the hottest part of the summer and then dies. O. tenuis seems to be a poor competitor. The frequency and severity of weed competition is directly related to other impacts like heavy grazing, discing, damming and draining that effect pool hydrology. The alteration of the length and timing of inundation can severely impact O. tenuis populations. Less inundation may not allow the requisite fungal growth to break dormancy, while too much may allow marsh and aquatic species to invade. O. tenuis seems to tolerate light to moderate grazing. This is probably due to the high densities of plants which can form a dense sod. The exudate makes the plant unpalatable to cattle. Timing of the grazing season to keep cattle off germinating and young plants is more important than stocking rates. Sheep have even less impact as they don't venture into pools while they hold water.

Species is wind pollinated. Cross pollination is extensive within pools. probably no genetic drift between populations. Seed heads are covered with a sticky substance which presumably adheres to bird feet or feathers. Seed is distributed within pools by floating as pool fills in fall or winter.