Kidneywood tree.

Each month, a gardener from Tohono Chul Gardens provides Oro Valley readers with information on native plant life. The mission of Tohono Chul Park is to enrich people's lives by connecting them with the wonders of nature, art and culture in the Sonoran Desert region and inspiring wise stewardship of the natural world.

By Leith Yong

The Coyote Mountains west of Tucson have many wonderful plants worthy of cultivation. Yes, some of them would be a tough sell for most weekend gardeners and snowbirds, but after seeing it on hikes in these mountains there was a thought, “Why don’t more people grow this?”
The tree that most stood out was the Eysenhardtia orthocarpa or Kidneywood. This small tree is in the Fabaceae or Legume family; the same as the well known Palo Verde and Mesquite. Kidneywood is found in the northern region of the Sierra Madre Occidental mountain range of eastern Sonora, Mexico and the extreme southwest boot heel region of New Mexico. In Arizona, it is found in Graham, Pinal, Cochise, Santa Cruz and Pima counties from 3,500 to 6,000 feet in altitude.

Kidneywood usually grows among rocks in canyons and hillsides where extra water is periodically available. This thornless tree has a height range of 10 to 20 feet and a spread of 6 to 12 feet making it a perfect choice for planting in a patio or small backyard. The fragrant leaves of Kidneywood are both cold and drought deciduous, but in mild winters or protected microclimates, it will retain its foliage through the winter. Starting in late spring and early summer, clusters of small, white, vanilla-scented flowers cover the tree and are a good nectar source for small butterflies like Hairstreaks and Blues.
Plant Kidneywood in full or reflected sun, as they tolerate heat, drought and poor soil once established. Keep in mind they grow faster with a deep soaking every ten days to two weeks from spring through fall. It naturally has an upright or vase shaped growth habit, but you will still want to spend some time for the first few years pruning to shape. If rabbits are a problem in your area, you may want to cage your young tree. Once Kidneywood is established it is virtually maintenance free!

It may be a little difficult to find Kidneywood in a local nursery, but just like that hike in the Coyote Mountains, it IS well worth the effort. This graceful yet rugged tree is just at home in an urban setting as it is on the steep hills and deep canyons, so the next time you are in the market for a small tree consider this under used member of the pea family.

From Tohono Chul:

Kidneywoods, a forgotten favorite