– Pachycormus discolor (2018)

By Mario Carlos (November 2018)

When I won this Pachycormus discolor as an attendance prize last August, my original plan was to present the before and after transformation of the young plant. After more than a year of care, I gave up that idea. The plant leafed out, but not a single branch of growth occured. I realized that this plant grows extremely slowly.

P. discolor is a Baja California native. The genus name, Pachycormus, is formed by “pachy,” meaning “thick;” and “kormos,” meaning “stump” – referring to the plant’s thick caudiciform trunk. P. discolor is also known as torote blanco or copalquín.

This pachyform tree is a member of the cashew family (Anacardiaceae) that can grow 10 to 30 feet tall in the ground if given ideal conditions. The thick trunk has exfoliating light gray/white/yellowish outer bark that reveals an olive green to blue-green photosynthetic inner bark. The tiny leaves are dark green, pinnately compound, pubescent and drought-deciduous.

The small flowers are cream to pink in color, giving the tree a rosy tinge when viewed from a distance. In its native habitat, P. discolor may bloom from May into September, depending on moisture levels.

This pachycormus usually grows in winter, when the plant gets more rain, and goes dormant during the hottest months of summer. In its natural habitat, it is often dwarfed by harsh conditions, resulting in a gnarly-branched, stunted tree that looks like natural bonsai.

Seed-grown plants will often form a caudexed trunk, both in natural desert habitat and cultivation. When grown in containers, however, the plants are generally much smaller and have a much slower rate of growth.

P. discolor grows best in high light and moderate heat, since it is a winter grower. It is marginally frost-tolerant, and the branch tips can get damaged at 32 degrees F. Temperatures below 25 degrees F can kill the plant.

In my observation, this plant leafs out in early autumn when the temperature gets cooler, then loses its leaves and goes dormant by summer. It can also be rather opportunistic, especially in cultivation. Sudden, pronounced changes in temperature for more than a week can trigger growth or even untimely dormancy.

Selected pruning of P. discolor will result in the best bonsai form, but may also slow the development of a thick caudex.

Anyone who grows succulent trees with the intention of bonsai presentation should consider Pachycormus discolor. The leaves are similar to those of Operculicarya, another choice bonsai genus that is also a bit touchier to grow. Since P. discolor grows very slowly, it may be justifiable to spend the extra money to buy an older, bigger specimen – an instant gratification!

Sources:
The Timber Press Guide to Succulent Plants of the World – Fred Dortort, 2011
San Diego Natural History Museum Ocean Oasis Field Guide – https://www.sdnhm.org/oceanoasis/fieldguide/pach-dis.html
University of Connecticut Biodiversity Education and Research Greenhouses – http://florawww.eeb.uconn.edu/198800001.html
The National Gardening Association Plants Database – https://garden.org/plants/view/119039/Baja-Elephant-Bush-Pachycormus-discolor