[Wikipedia] Rarity, Pathogenic Risk, Description: Arctostaphylos densiflora, known by the common name Vine Hill manzanita, is a very rare species of manzanita. It is endemic to Sonoma County, California, where it is known from only one extant population of 20 to 30 individual plants. These last wild members of the species are on land near Sebastopol which is owned and protected by the California Native Plant Society. In addition, there are five to ten plants of this manzanita taxon growing on private property about a mile away.[2] The local habitat is mostly chaparral on sandy shale soils. Pathogenic Risk The entire wild population is infected with the root pathogen Phytopthera cinnamomi and subject to mortality, which could result in species extinction.[3] Ecological Relationships The flowers of this species provide nectar for butterflies and native bees in the spring, berries provide food for birds in the late summer, and the low-growing habit of the plant make it a good home for California valley quail and wrentit nests. (Lowe 1999)[5] Habitat Species differentiation A. densiflora likely appeared about 1.5 million years ago, although the Arctostaphylos genus itself arose in the Miocene era.[7] (link added by Mary Ann Machi)