Pachycormus is a monotypic genus of flowering plants in the cashew family (Anacardiaceae), containing a single species, Pachycormus discolor, commonly known as the Baja elephant tree, torote blanco, or copalquín. It is endemic to the Baja California peninsula of Mexico.
The genus is instantly recognizable by its swollen, caudiciform trunk — typically 60 to 80 cm in diameter — which gives rise to its name and its elephant-tree common name. The outer bark is smooth and papery, exfoliating annually to reveal a spongy, blue-green photosynthetic inner bark beneath. This inner bark exudes a milky sap that hardens into a clear gum or resin. The overall growth habit is gnarled and often bizarre, and has been described variously as resembling "the proboscis of an elephant holding a nosegay" or "a huge radish protruding from the ground."
Pachycormus discolor is drought-deciduous, spending much of the year leafless and dormant. After rainfall, dark green pinnately compound leaves emerge; in late spring and summer the leaves yellow and drop, giving way to showy panicles of dioecious flowers in yellow, pink, or red depending on variety. Blooming continues from May into September. The plant is classified as sarcocaulescent — storing water in its thick succulent stem — an adaptation to the extreme aridity of its desert habitat.
Three varieties are recognized, each restricted to different sub-regions of the peninsula: var. pubescens, var. veatchiana, and var. discolor. The species occupies the Baja California desert and Vizcaino desert, with populations also in montane ravines of the Sierra de La Giganta and on Gulf islands, from sea level to about 460 m elevation.
Etymology
The name Pachycormus derives from the Greek pachys (“thick”) and kormos (“trunk”), a direct reference to the species' massively swollen caudiciform trunk. The common name “Baja elephant tree” similarly alludes to the trunk's great girth, likened to an elephant's proportions; the same common name is also applied to the unrelated Bursera microphylla.
Distribution
Pachycormus discolor is strictly endemic to the Baja California peninsula of Mexico, occurring in both Baja California and Baja California Sur. The three varieties occupy distinct portions of the peninsula: var. pubescens ranges from San Fernando Velicatá in the north to near La Paz and various Gulf islands; var. veatchiana is confined to the western Vizcaino desert margins, Cedros Island, and Natividad Island; var. discolor occurs on the islands of Magdalena Bay and the western flanks of the southern Sierra de La Giganta. The species grows from sea level to approximately 460 m elevation.
Ecology
The species is adapted to extreme aridity: summers bring temperatures of 34–45°C and rainfall comes almost entirely from Eastern Pacific hurricanes in August–October, with some years receiving no rain at all. The plant responds by being drought-deciduous — leafless and dormant through dry periods — and by storing water in its massive succulent trunk. In ravines of the Sierra de La Giganta it can form dense, impenetrable groves; on wind-exposed Pacific coastal sites the growth habit becomes prostrate or sprawling.
Cultivation
Pachycormus discolor is cultivated by caudiciform succulent enthusiasts as a container specimen. Plants require full sun and are marginally frost tolerant: foliage sustains tip damage at 0°C and the plant is killed at approximately −4°C. Only seed-grown individuals develop a prominent caudex; cuttings do not form the characteristic swollen base.
Cultural Uses
The bark of Pachycormus discolor was historically harvested and exported to Europe in considerable quantities for use in leather tanning.
