Calistoga Allocarya

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Calistoga Allocarya

Plagiobothrys strictus

ListedOctober 22, 1997
FamilyBoraginaceae (Borage)
DescriptionAn annual, herbaceous wildflower.
HabitatPools and swales associated with hot springs and small geysers in grass-lands.
ThreatsHabitat loss and damage caused by recreational activities, airport maintenance, urbanization, and other disturbances.


Calistoga allocarya, Plagiobothrys strictus, is a small and erect annual herb of the borage family (Boraginaceae) that grows 4-15 in (10-38 cm) tall. The nearly hairless plant has either a single stem or branches from near the base. The linear lower leaves are 1.5-4 in (3.8-10 cm) long. White flowers, small and usually paired, appear in March to April in a slender, unbranched inflorescence. The fruit is an egg-shaped nutlet about 0.6 in (1.5 cm) long, keeled on the back, with wart-like projections without any prickles. Plagiobothrys greenei, P. lithocaryus, P. mollis var. vestitus, P. stipitatus, and P. tener have ranges that overlap with that of P. strictus and occur in similar habitats, but they neither resemble P. strictus nor have they been found at the known P. strictus sites.


Calistoga allocarya is found in pools and swales adjacent to and fed by hot springs and small geysers in grasslands at elevations between 300 and 500 ft (91 and 152 m).


Three historical populations occurred within a two-mile radius of Calistoga in Napa County, one of which was extirpated by urbanization and agricultural land conversion. One remaining population occurs near a geyser and some undeveloped thermal hot springs, while the other occurs at the Calistoga City Airport.


Calistoga allocarya is threatened by recreational activities, airport maintenance, urbanization, and destructive random events. Since this species occurs at the same sites as Napa bluegrass, they face nearly identical threats.

One historical occurrence and over 70% of the original habitat of Calistoga allocarya have been extirpated by urbanization and conversion of land to vineyards. The two remaining populations are threatened by urbanization. The Calistoga Airport location had a population of about 5,000 individuals in a 2,000 square foot area in 1994. The number of individuals in this population fluctuates considerably, perhaps due to variations in spring rainfall between years. Airport maintenance and operational activities, including vehicle traffic, parking by vehicles on the plants, grass mowing, and any land use changes, currently threaten this population, and any future development at the site would likely threaten the remaining plants.

Grass mowing is done periodically through the spring and summer to reduce fire and aircraft safety hazards. Airport users include a spray plane service, recreational gliders, and associated tow planes. Service vehicles for the planes and the private vehicles of the customers harm this plant there, especially during the spring and summer when airport use increases.

The other population is scattered over a ten-acre area bisected by an asphalt road on private land near Myrtledale Hot Springs in the City of Calistoga. The number of individuals in this population was estimated to be in the hundreds, although it has been impossible to verify current numbers because the landowner has denied access to the site in recent years. The landowner has proposed to build a hospital on this site, but he has been unsuccessful due to the current zoning status of his property. Both populations of Calistoga allocarya depend on moisture from adjacent hot springs or surface runoff; any action that alters the hydrology or flow from these hot springs would be very damaging.

Conservation and Recovery

Both populations of the Calistoga allocarya are on private land, and are threatened by various disturbances associated with human activities. These populations must be protected. This could be done by acquiring the critical habitats and establishing ecological reserves, or by negotiating conservation easements with the private landowners. The Calistoga allocarya should be monitored at its known habitats, and searches made to see if there are any undiscovered populations. Research should be conducted into its biology and habitat needs. Additional populations should be established in suitable habitats.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121

U. S. Fish and Wildlife Service
Sacramento Fish and Wildlife Office
2800 Cottage Way, Room W-2605
Sacramento, California 95825-1846
Telephone: (916) 414-6600
Fax: (916) 460-4619


U. S. Fish and Wildlife Service. 22 October 1997. "Endangered and Threatened Wildlife and Plants: Determination of Endangered Status for Nine Plants From the Grasslands or Mesic Areas of the Central Coast of California." Federal Register62 (204): 54791-54808.