Hesperocyparis forbesii (Jeps.) Bartel — Tecate western-cypress

Introduction

The Tecate western-cypress, Hesperocyparis forbesii, is an evergreen tree or large shrub of scattered chaparral-covered mountains in southern California and northern Baja California. It is usually small to moderate in stature, often multitrunked, with smooth reddish-brown bark, light-green foliage, and relatively large globose cones. Tree TSAR places it in the Arizonica Clade, a major shift from historical classifications that treated it as a variety or subspecies of Guadalupe Island H. guadalupensis.

The two species are now separated by multiple evidence systems. Their population structures, cone-opening behavior, and genome-scale positions differ, even though gross morphology can be deceptively similar. Li et al. (2026) sampled one H. forbesii accession from California and one from Mexico and recovered them in the Arizonica radiation; H. guadalupensis is instead a Macrocarpa-clade species associated with H. stephensonii.

Horticultural and Agricultural Uses

Tecate western-cypress is a specialist native and conservation plant rather than a major commercial cypress. Its compact habit, smooth bark, and adaptation to dry chaparral settings can make it attractive in compatible southern California and Mediterranean-climate landscapes, but seed provenance and fire ecology should remain central when the species is grown for conservation or research.

Propagation by seed is straightforward when viable seed is available, but the strongly serotinous cones are adapted to retain seed until intense heating or branch death. In cultivation, cone collection and artificial opening can bypass the ecological trigger; that practical convenience should not obscure the species’ dependence on fire timing in the wild.

Conservation Concerns

Tecate western-cypress is restricted to a small number of metapopulations in southern California plus isolated stands in northern Baja California. Its principal modern threat is too-frequent fire. The species is adapted to stand-replacing wildfire, but human-caused ignitions have shortened fire intervals in parts of its range, creating an “immaturity risk” when young stands burn before they produce enough cones to replace themselves (Brennan & Keeley 2019).

Long-term monitoring after the 2003 Mine/Otay Fire showed that recruitment can initially be abundant while the occupied area still contracts where prefire cone production was low or fire intensity was extreme. Conservation therefore depends on more than counting postfire seedlings: managers need to protect the spatial distribution of stands, allow sufficient time for reproductive maturation, and account for interactions between drought, growth rate, and future fire climate (Brennan & Keeley 2019).

Additional Information

Plants of the World Online — Hesperocyparis forbesii (opens in a new tab): Current Kew nomenclatural and distributional treatment.
Trees and Shrubs Online — Hesperocyparis forbesii (opens in a new tab): Horticultural and historical account.
U.S. Geological Survey — postfire population dynamics (opens in a new tab): Research summary and DOI for the long-term Tecate cypress fire-demography study.
Rosas-Escobar et al. 2011 — plastid diversity (opens in a new tab): Population-genetic comparison with Guadalupe Island western-cypress.

References and Further Reading

Brennan TJ, Keeley JE (2019) Postfire population dynamics of a fire-dependent cypress. Plant Ecology. https://doi.org/10.1007/s11258-019-00939-8 (opens in a new tab).

Li J, Jia S, Wu D, Tao W, Ruhsam M, Mao K (2026) Phylogenomics reveals the reticulate evolution and biogeographic history of New World cypresses, Hesperocyparis (Cupressaceae). Cladistics 42(2): 109–127. https://doi.org/10.1111/cla.70021 (opens in a new tab).

Rosas-Escobar P, Gernandt DS, Piñero D, Garcillán PP (2011) Plastid DNA diversity is higher in the island endemic Guadalupe cypress than in the continental Tecate cypress. PLOS ONE 6(1): e16133. https://doi.org/10.1371/journal.pone.0016133 (opens in a new tab).

Royal Botanic Gardens, Kew (2026) Hesperocyparis forbesii (Jeps.) Bartel. Plants of the World Online. https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A60451550-2 (opens in a new tab).