Nolina interrata is one of the rarest plants in North America — a beargrass restricted to approximately 9,000 plants total in existence, all within a six-square-mile area of central San Diego County, California, and fewer than 100 individuals across the border in the Valle de Guadalupe region of Baja California. First described in 1946 by Howard Scott Gentry from a collection made near El Cajon, it is a plant of chaparral on gabbro and metavolcanic clay soils — a habitat so specific that the species’ entire world range could fit within a small suburb.
Taxonomy and nomenclature
Described by Gentry in 1946. Family Asparagaceae, subfamily Nolinoideae. Some authors have treated it as conspecific with Nolina parryi, but the most recent taxonomic treatment (Dice 1988) confirms it as distinct. The species was proposed for federal threatened listing in 1995 but the proposal was withdrawn in 1998 after conservation measures were deemed sufficient (67% of known occurrences on protected lands managed by the California Department of Fish and Game and The Nature Conservancy).
Common names
Dehesa nolina, Dehesa beargrass, San Diego beargrass (English).
Morphological description
Habit
Acaulescent. Produces clusters of rosettes from branching, horizontal, subterranean caudices arising from lignotubers. Reproduces clonally, forming patches of genetically identical individuals — a trait documented during a San Diego Zoo Wildlife Alliance seed-banking expedition to Baja California.
Leaves
Stiff, waxy, blue-green (glaucous), 10–45 per rosette. Thick and somewhat fleshy at the base, shreddy and serrated along the edges. Length 30–150 cm, width 12–35 mm.
Inflorescence and flowering
Paniculate flower stalks 0.5–1.6 m (1.6–5 ft) tall. Flowering is sporadic in the absence of fire; fire triggers mass resprouting and subsequent mass flowering. The San Diego Zoo expedition to Baja California found no flowering or seed in the year of their visit — the plants had not experienced recent fire.
Distribution and natural habitat
Central San Diego County (about ten occurrences within a six-square-mile area near El Cajon) and Valle de Guadalupe in north-western Baja California (fewer than 100 individuals). Habitat: chaparral and mixed chaparral on clay soils derived from gabbro or metavolcanic bedrock. Cool, wet winters and hot, dry summers. The species is associated with specific soil types — it is not found on adjacent sandstone or limestone.
Conservation
Although the total population (~9,000 plants) and relatively well-protected habitat led to the withdrawal of the federal listing proposal, significant threats persist:
- Urbanisation: San Diego County development continues to fragment habitat.
- Invasive weeds: particularly in the chaparral matrix surrounding the nolina populations.
- Climate change: altered fire regimes and drought threaten chaparral communities.
- Wild collection: identified by USFWS as a continuing threat.
- Clonal reproduction: patches may represent single genets, meaning genetic diversity is lower than raw population numbers suggest.
The San Diego Zoo Wildlife Alliance’s “Baja Rare” project is actively researching the Baja California populations, collecting seed for banking and mapping population extent.
Not a garden plant
Like Nolina brittoniana, this species is included for conservation documentation. It is not available in the nursery trade and should never be collected from the wild.
References
POWO (2026). Nolina interrata. Plants of the World Online, Kew.
USFWS (1998). Withdrawal of proposed rule to list Nolina interrata as threatened. Federal Register, October 13, 1998.
San Diego Zoo Wildlife Alliance (2021). Team Nolina Baja Excursion.