Napa Bluegrass

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Napa Bluegrass

Poa napensis

ListedOctober 22, 1997
FamilyPoaceae (Grass)
DescriptionA tufted, perennial grass with flower clusters that occur as a pale green to purple, condensed, and oblong-oval panicle.
HabitatGrasslands and moist, alkaline meadows fed by hot springs.
ThreatsHabitat destruction caused by urbanization, and damage by recreational activities, airport maintenance, and other disturbances.


Poa napensis (Napa bluegrass) is an erect, tufted perennial bunchgrass in the Poaceae (grass) family that reaches 4 in (10 cm) in height. Leaves are folded, stiffly erect, and 0.04 in (1 mm) wide, with the basal leaves 8 in (20 cm) long and upper stem leaves to 6 in (15 cm) in length. A few stiff, erect flowering stems appear in May and grow 27 in (69 cm) in height. Flower clusters occur as a pale green to purple, condensed, and oblong-oval panicle that is 4-6 in (10-15 cm) long and 0.8-2.0 in. (2-5 cm) wide.

Poa napensis most closely resembles Poa unilateralis (ocean bluff bluegrass), but differs in leaf and panicle form and habitat.


Napa bluegrass is found in grasslands and moist, alkaline meadows fed by hot springs at an elevation range of 340-400 ft (104-122 m).


The historical range of Napa bluegrass was within a radius of four miles of Calistoga, but the growth of the town and the development of the hot springs have greatly restricted its distribution. Only two populations of the species are now known, both located on private land and not protected. The Myrtledale Hot Springs population is confined to a 1,100 sq ft (102 sq m) area, and the second group of 100 plants occurs nearby.


Napa bluegrass is threatened by recreational activities, airport maintenance, urbanization (including potential construction of a hospital), and random events. The historic habitat of Napa bluegrass has been so reduced by the development of health spas and resorts in the City of Calistoga and by construction, maintenance, and operational activities at the Calistoga Airport that only two small populations remain.

The Calistoga Airport remnant was believed extirpated as a result of construction activities in 1981; no plants were found later that year, but 500 plants were counted there in 1987, 150 in 1994, and 150 in 1996. Grass mowing, vehicle traffic, and vehicle parking have already damaged and will continue to threaten this population. Grass mowing is done at regular intervals 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 actively harm this plant there, especially during spring and summer when air traffic increases. The only other population is near Myrtledale Hot Springs in the City of Calistoga, where several thousand plants were reported in the early 1980s. The landowner has denied access to the property in recent years, and he has proposed to build a hospital on this site, although he has not been successful in getting this project approved due to the current zoning status of the land. Both populations of Napa bluegrass 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

The only two known populations of the Napa bluegrass are on private land, and are threatened by development and other activities. Its critical habitat should be acquired and designated an ecological reserve, or conservation easements negotiated with the landowners. The populations of the Napa blue-grass should be monitored, and research undertaken into its biology and habitat needs.


U. S. Fish and Wildlife Service
Division of Realty-Sacramento Field Office
Federal Building
2800 Cottage Way, Room W-2610
Sacramento, California 95825-1846
Telephone: (916) 414-6446
Fax: (916) 414-6486

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


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 Register 62 (204): 54791-54808.