Rare Plants of PHP

The Pine Hill Preserve's rare plants are a collection of eight rare plant species that share the unusual growing conditions of a small area of western El Dorado County. They grow in a roughly oval area centering around Green Valley Road and stretching from Folsom Lake in the north to Highway 50 in the south. Three of these rare plants are endemic to the Pine Hill region, meaning that they grow nowhere else in the world. Another two species are nearly endemic, with only a few small colonies of the plants found elsewhere.

This surprising assemblage of rare species is part of a unique plant community confined to soils known as the Rescue soils series, named after the nearby community of Rescue. These soils are associated with the broader classification of gabbro soils, broader classification of gabbro

soils, and cover approximately 30,000 acres in the area described above. Gabbro soils have unusual properties derived from the underlying gabbro rock : they are generally red, mildly acidic, rich in iron and magnesium, and often contain other heavy metals such as chromium.

The gabbro rock from which these soils are derived was originally formed deep in the earth's crust from molten rock about 165 million years ago. Through uplift of the crust and erosion of the ancestral Sierra Nevada, these rocks eventually became exposed at the earth's surface. Gabbro rocks contain mostly dark minerals and visible crystals are common. Exposed surfaces often weather to a reddish color due to the iron content of the rocks. Outcrops of another unusual rock type, serpentinite, also occur in the Pine Hill area. The soils that result from the weathering of serpentinite, known as serpentine soils, have similarities to the soils from gabbro rocks and support some of the same species.

740 distinct plant species have been recorded in the Rescue soil series and adjoining serpentine and metamorphic rocks. This means that about 10% of the native plant species known in California are represented within this tiny fraction of the state, making it a nationally significant site of species diversity.