Vine Hill Preserve

About the Preserve

Vine Hill Preserve (VHP) is an isolated 1.6 acre preserve in a region that once supported a flora unique to the Vine Hill Region in western Sonoma County, CA (Roof 1972).

VHP, owned and stewarded by the California Native Plant Society, Milo Baker Chapter (CNPS MB Chapter) since the mid-1970’s, was established to protect one of the last remaining populations of Vine Hill manzanita Arctostaphylos densiflora which occurred naturally along the steep southern slope of the preserve. Most habitat once occupied by the unique flora of the Vine Hill region, referred to as the Sonoma Barrens (Roof 1972), had long been converted to agricultural use and rural residential development; VHP arguably became its last refuge. The CNPS MB Chapter subsequently introduced two additional species to VHP, Vine Hill Clarkia Clarkia imbricata, and glory bush Ceanothus gloriosus var. exaltatus. The Vine Hill manzanita, state listed endangered, and Vine Hill clarkia, state and federally listed endangered, are approaching extinction in the wild; the sole known remaining occurrence of these two species are at VHP, all other historic populations are now presumed to be extirpated.

Vegetation management, small scale restoration measures and research conserve the rare species at VHP. Management of suitable habitat for the rare plants includes removal of competing invasive species, including but not limited to coast live oak Quercus agrifolia, black oak Quercus kellogii, douglas fir Pseudotsuga menziesii, common manzanita A. manzanita, madrone Arbutus menziesii and velvet grass Holcus lanatus; restoration includes establishing rare plant species in areas currently occupied by non-annual grasses and coast live oak.

Vine Hill Ceanothus

Vine Hill Ceanothus, Ceanothus gloriosus var. exaltatus

Vine Hill Clarkia

Vine Hill Clarkia, Clarkia Imbricata

Vine Hill Manzanita

Vine Hill Manzanita Arctostaphylos densiflora

Preserve Background

The VHP was purchased by the Nature Conservancy in 1972 and immediately deeded to CNPS, following a plea published by James Roof in the Four Seasons (Roof 1972) to preserve this important population of Vine Hill manzanita under threat of extirpation from development. The majority of the property at the time contained a cultivated vineyard, but naturally occurring Vine Hill manzanitas, Vine Hill ceanothus and associated species occurred in the narrow strip along the steep southern bank (Roof 1972).

The VHP currently supports the last extant population of state listed endangered Vine Hill manzanita, the last remaining population of federal and state listed endangered Vine Hill clarkia (introduced), and one of two confirmed extant populations of Vine Hill ceanothus, CNPS list 1B. Threats to these rare species at VHP include risk of extinction by stochastic events, loss of habitat due to encroachment of non-native species and conversion of habitat to closed oak woodland due to community succession.


Today VHP, in addition to providing a safe refuge for the rare plants, sustains many native plant species. The vegetated areas not occupied by rare plants contain a number of native plant species, all of which have maintained or established themselves naturally. Two plant communities predominate, oak woodland dominated by coast live oak, black oak, madrone, California blackberry Rubus ursinus, poison oak Toxicodendron diversilobum and common manzanita, and native grassland dominated by California oatgrass Danthonia californica and wood rush Luzula comosa. Uncommon native species in the oak woodland include salal, beargrass, and bay laurel Umbellularia californica; uncommon native species in the open grassland and woodland interface include coffeeberry, coyote bush Baccharis pilularis, bracken fern, Solidago Solidago spathulata, thin-lobed Horkelia and rein orchid. Common non-native species within the grassland include smooth and rough cat’s ear Hypochaeris glabra, H. radicata, silver European hairgrass Aira caryophyllea, and sheep sorrel Rumex acetosella. Invasive non-native species on the preserve include velvet grass Holculus lanatus, Spanish broom Spartium junceum, Monterey pine Pinus radiata, and English ivy Hedera helix. With the exception of the velvet grass, which dominates one large area and is expanding its range, the other non-native invasive species are controlled by current management practices.

For more about VHP vegetation, view A Flora of Vine Hill Preserve.

Stewardship Activities

  • Removal or reduction of velvet grass and other non-native invasive species from the Preserve; focusing on open grassland and areas occupied by rare-plants
  • Reduction of native tree and shrub species such as coast live oak and common manzanita, from grassland and areas occupied by rare-plants, and adjacent areas threatening to shade Vine Hill manzanita habitat
  • Removal of all plant debris from stewardship activities, and from illegal dumping
  • Remove old barbed wire fencing and T bars
  • Annual or biennial population census of Vine Hill clarkia
  • Monitoring health and survival of naturally occurring and introduced Vine Hill manzanita