Elephant Tree
Bursera microphylla
Family: Burseraceae
OTHER NAMES
Spanish: torote blanco, copal, palo colorado, torote rojo, torote colorado, cuajiote blanco, torote
CHARACTERISTICS
Elephant trees are special and unusual plants we call “caudiciform” or fat succulent plants. They are in the frankincense family and are the new world cousins of that old world group of fragrant plants. They can grow up to 20’ tall in frost free conditions, though the populations found in Arizona are usually stunted (frost-pruned shrubs). The trunk is iridescent, coppery, with pealing bark. The trunks of these plants exude a hard waxy substance called copal. The leaves are resinous, shiny, and squirt terpenes when pulled from the stem. Small flowers yield aril-covered seeds.
LANDSCAPE USE
Though these plants are trees in frost-free locations, they are mostly seen in our region as shrubs or special container specimens.
GROWING CONDITIONS
AN EXPLANAITION OF TERMS USED
SUN full to part sun, even reflected heat
WATER low, can live on rainfall when established. If pushing this plant to grow, give extra water during the warm season
SOIL not picky, but well-drained
HARDINESS protect from frost, plants can tolerate temperatures in the mid to high 20s°F, but will have some tip damage
BASIN high zone
CONTAINER does very well in containers and make great bonsai
NUTRITION low
MAINTENANCE very little
ECOLOGY
Bursera species often can photosynthesize when leafless through their iridescent trunk, much like ocotillos do. Larval host for the Dingy Purplewing (Eunica monima).
A special population of this species, in the Waterman Mountains in Ironwood Forest National Monument, has much larger leaves than the typical species. It is thought to be a population that was hybridized with Bursera fagaroides eons ago when that species was more prevalent in Arizona.
ETHNOBOTANY
The copal is burned like frankincense. The plant has many medicinal uses by the various people who live within its range. The stems are used to make coil baskets.
NATURAL DISTRIBUTION
Found on rocky slopes and in canyons from 500-3,500’ across southwestern Arizona into Sonora and into Baja California, and further south to Zacatecas. It is a distinctively Sonoran Desert species. Its natural distribution is only missing from the most northern and eastern parts of the Sonoran Desert.
TAXONOMY AND NAME
This species is in the Burseraceae, the frankincense family. There are 120 species of Bursera. The trees are native (often for many species endemic) to the Americas, from the southern United States south through to northern Argentina, in tropical and warm temperate forest habitats.
The genus is named after: Joachim Burser, German/Danish botanist,1583-1639. Microphylla means small leaf, referring to the plants relative small leaf size.
There are many other Bursera species that, if you have a protected microclimate with little to no frost, you can grow to tree size.
Bursera microphylla on iNaturalist
Bursera microphylla on SEINET
The resinous foliage actually squirts aromatic sap when pulled from the stem. Flowers are white to yellow and small. Photo by tomfeild on iNaturalist
The trunks of these plants are spectacular with their peeling bark and shiny trunk. Photo by brymalplants, iNaturalist
Plants regularly exposed to cold temperatures are often short from being frozen back. Fat trunks can be found under these plants in rocky soils, protected at the base by the rocks. Many plants in the US are short and shrubby. Photo by Fred Melgert / Carla Hoegen, iNaturalist
Fruits are drupes with seeds inside. The seeds are yellowish. Photo by David Greenberger, iNaturalist