By Pete Duncombe
Spring is an exciting time in the Gardens as the doldrums of winter are replaced by the emerging leaves and flowers in increasing abundance as the season progresses. One of the most striking signs of spring are the flowering trees that begin with the early-blooming fruit trees and follow soon after with more ornamental varieties.
One such genus that grabs your attention is Bauhinia. This outstanding genus includes flowering trees with unique blossoms resembling orchids in the spring into summer and in some cases, through fall. This large tropical genus was named by Linnaeus in 1753 in recognition of Jean and Casper Bauhin. Both brothers were Swiss botanists during the 16th Century. The distinctive bi-lobed leaves are fused at the base and resemble cloven hooves.
These members of the pea family (Leguminosae) are widely distributed throughout tropical and subtropical regions of the world with good representation in both Asia and the Chihuahuan Desert. While the Asian species are valued for their dramatic size and color, they are very subject to freezing, and therefore not a good choice for cold desert regions. The Chihauhuan native species of Bauhinia, however, are well suited to the harsh conditions of the desert.
The Chihuahuan orchid tree, Bauhinia macrantha, hails from the Western Sierra Madre of Chihuahua, Mexico. It is a proven variety that can take the cold down to at least 10°F. Though it has been a somewhat difficult variety to obtain until recently, its addition yields another useful tree of this class.
The Chihuahuan orchid tree has large flowers that range from purple to pink that burst into bloom from March through May. Its large cloven leaves remain virtually evergreen above freezing temperatures. Its combination of striking foliage and showy blooms make a strong statement in the garden.
Bauhinia macrantha has a slow growing, rounded form to 12-15 feet high and wide with a natural vase shape that is easy to maintain with minimal pruning. Its open structure supports under planting with succulents and perennials that benefit from the filtered shade it provides. It is hardy in USDA Zone 7-11, thriving in partial shade to full sun, requiring little water and well-drained soil conditions. Flowering will be best, however, if it receives a minimum of six hours of sun.
There are no pest problems to speak of with this species. They are heat and drought tolerant, but benefit from regular watering in the garden to keep up the vigor and maintain the bloom. The fragile branches are easily broken from strong winds but readily recover from the damage. Planting in a more protected location minimizes the problem.
The Chihuahuan orchid tree is deciduous in the cold weather but is quick to green up when the warmth returns. They are propagated easily from seed, but more difficult from soft wood cuttings in the spring. They are not self-fertile however, so two or more plants are required to produce viable seed.
The Bauhinias are very useful flowering shrubs or small trees that work well in the garden, as a specimen, or in association with other plants providing a sensational accent in the landscape. The beautiful flowers are attractive to butterflies and the scale is ideal for a courtyard or small back yard plantings.
We have also grown the Anaconda orchid tree, Bauhinia lunarioides, native to the southern Texas Hill Country, for a number of years and have only recently added the closely related Chihuahuan orchid tree. The two species are similar in character, though, B. lunarioides is a medium shrub, or small tree (6-10 feet) with delicate, unusual leaves that are divided into pairs of oval leaflets and showy white flower clusters reminiscent of orchids. Others Bauhinias may potentially also be grown, but of the two species we have tried, the Chihuahuan orchid tree is certainly the showier and more interesting variety that we have seen.
Pete Duncombe is the plant curator at the Springs Preserve in Las Vegas, NV.