Spartina foliosa

Spartina foliosa is a species of grass known by the common name California cordgrass. It is native to the salt marshes and mudflats of coastal California and Baja California, especially San Francisco Bay. It is a perennial grass growing from short rhizomes. It produces single stems or clumps of thick, fleshy stems which grow up to 1.5 meters tall. They are green or purple-tinged. The long, narrow leaves are flat or rolled inward. The inflorescence is a narrow, dense, spike-like stick of branches appressed together, the unit reaching up to 25 centimeters long. The lower spikelets are sometimes enclosed in the basal sheaths of upper leaves.

This native plant is seriously threatened by the invasion of its non-native relative smooth cordgrass (Spartina alterniflora). The latter was introduced to San Francisco Bay in the 1970s and it quickly began to hybridize with S. foliosa, leading to the near-extirpation of the once-common native plant. The two species reproduce at the same time of year, and the invader sheds large amounts of pollen that fertilize the flowers of the native, so that the majority of the native plant's offspring are hybrids. There are almost no pure individuals of S. foliosa left, as most plants in the area are hybrids: this is an example of genetic pollution. Hybrids of the two species have spread rapidly because they are much more genetically fit than either parent, an example of hybrid vigor. Pure S. foliosa will probably become extirpated from San Francisco Bay, and only its hybrids will remain.