Bet on Bauhinia

Bauhinia purpurea (purple orchid tree) is an Asian species that needs more water than its Mexican counterparts. Photo by Gary Irish

I am frankly enamored of the genus Bauhinia. It honors two 16th-century Swiss botanists, the twin brothers John and Caspar Bauhin, because the leaves in all species of the genus are united at the base. Some are barely joined, while others are almost entirely so and whether they are rounded or end in a sharp tip the leaves look much like a hoof.

Of course it is their extraordinary flowers that have won my heart and that of so many gardeners. Often called orchid trees, the flowers are made up of five irregular, usually widely spaced petals in purple, lavender, white, pink, orange and yellow. Although they are legumes, this floral style is unusual in the family. I don’t get the orchid connection personally, but it is a lovely name for such arresting flowers.

Bauhinia is widely distributed through the subtropical and tropical regions of the world. This large range means that there are impressive differences in cold and heat tolerance, flowering color and season, and form. Within the genus there are trees, shrubs and rambling vines and many are excellent choices for USDA Zones 8-10.

The trees are often brittle, losing limbs in high wind. But like most legumes, they recover and resprout quickly from such damage. In many of the shrubs, what looks like the central stems die out after a few years. These are easily pruned out thus allowing the jam of new stems at the base to grow and mature.

Although many bauhinia are extremely resistant to high heat, even the most drought tolerant need regular watering in the summer to maintain flowering and vigor. They have few pests, leaf cutter bees may cause superficial damage, and suffer from virtually no disease. Almost all species are deciduous in severe cold or when extremely dry, but recovery is quick. This handy trait helps if plants are troubled by a large insect infestation. Simply strip the leaves, plants recover quickly, and the pest has moved on.

In the garden, all bauhinias make splendid specimen or focal plants owing to their abundant and long-lasting flowering. In all forms they blend well with other shrubs, flowering or otherwise, or with groups of understory plants under large trees. The tree forms may be all the tree that is needed in a small patio or courtyard.

(Top to Bottom) Bauhinia lunarioides (Anacacho orchid tree) grows 6- to 10-feet tall. Bauhinia galpinii (Red orchid bush) grows as a sprawling bush up to 10 feet tall but spreading as far as 15 feet. Bauhinia divaricata (Mexican orchid tree) is fragile in high winds, but more salt tolerant than most bauhinia. Photos by Gary Irish

Propagation is easy from seed. Seeds germinate quickly after a hot water soak. Bottom heat or warm weather also speeds gemination. Many can be propagated from cuttings, but this has mixed results. The vining forms strike readily, but the tree and shrub forms can be difficult and have low success rates. Soft wood works best in the spring or early summer.

Bauhinia species
Gardeners have long been familiar with the Asian species of orchid tree; purple orchid tree (Bauhinia purpurea and B. variegata) and the irresistible Hong Kong orchid tree (B. × blankeana). Both are large, full flowered trees that do best in deep, rich soils with ample water and winter temperatures well above 25°F. While these are handsome garden specimens, there are a number of other bauhinias that make extraordinary garden plants using much less water.

Anacacho orchid tree (Bauhinia lunarioides) is native to a small part of southwestern Texas but a large area of adjacent Mexico. It thrives in highly alkaline, rocky soils. Anacacho orchid tree grows 6 to 10 feet tall and up to 6 feet wide with an open, loosely branched habit. Leaves are small, crowded and dark green. While the white-flowering form is most common in the trade, pink is the common color in nature. The small flowers are congested into umbel-like arrangements along the stems. Bloom is heaviest in the spring but intermittent through the fall. It is hardy to 15°F and maybe more.

Mexican orchid tree (Bauhinia divaricata often erroneously labeled B. mexicana) is widely distributed in northern Mexico, south to Nicaragua and into the Caribbean Islands with a disjunct population in the Cape Region of Baja California Sur. It’s unparticular about soil as long as it is well drained. It is reported to be more salt tolerant that most bauhinia. Mexican orchid tree grows 6 to10 feet tall, rarely to 20 feet, with a spreading, open habit. The leaves are bright green, fuzzy below and smooth above and end in a sharp tip. The small flowers open white but fade to pink and form in successive waves through the summer and early fall. They are so prolific they coat the plant when in full flower. Trees are fragile and suffer wind damage easily. This species suffers leaf loss at 20°F, dies to the ground at 15°F, but recovers quickly. It is reported to be resistant, or some say repulsive, to deer.

Chihuahuan orchid tree (Bauhinia macranthera) covers a wide range through the Chihuahuan desert region of northeast Mexico. This is an open branched tree growing to 20 feet tall with a nearly equal spread. The large, deep green leaves have a deep cleft between the rounded leaflets. The flowers range in color from deep lavender to pink and are up to 3 inches across. They are held along the top of the branches, singly or in clusters with the overall effect of corsages laid on a tray. This orchid tree flowers mainly in the late spring, occasionally repeating in the fall. It suffers slight tip damage at 20°F and like many of this genus is fragile and will lose limbs in high winds.

Pata de Vaca or white orchid tree (Bauhinia forficata) has long been a great favorite of mine. Up to 40 feet tall, this orchid tree has large, deep green leaves and unlike most bauhinia, there are tiny thorns on the joints of the stems. These leaves accent the big, pure white, fragrant flowers that bloom from late spring to fall. This exquisite bauhinia is hardy to about 10°F and tolerates any well-drained soil.

Yellow bauhinia (Bauhinia tomentosa) comes from the coast of South Africa into India and Sri Lanka. This is a small tree or shrub growing up 6 to 13 feet tall and spreading to 8 feet. It has such an intricate branching pattern that individual plants may be upright, spreading or even cascading to the ground.

Leaves are light green and are firm, almost leathery. Flowers are a clear, bright yellow with a maroon, almost black, throat. The flowers are more closed than most of the genus, often falling like bells and occur prolifically during the hottest part of the summer. Plants are hardy to at least 25°F but probably more.

Climbing Chinese orchid tree (Bauhinia yunnanensis) is a twining woody vine. Often deciduous through the winter, the small, deep green leaves with rounded tips emerge early in the spring. The small, lavender flowers form from mid-summer to late fall and while each is a delicate bloom they are so prolific they smother a fence. This species does well in alkaline soils but like most bauhinia need good drainage. Root hardy to single digits, this is an exciting bauhinia that deserves to be more widely grown.

Red orchid bush (Bauhinia galpinii) is a charming, but unusual, bauhinia. It has bright brick-red to light orange flowers from mid-summer to fall, the foliage is deciduous in the late winter through spring, and it grows as a sprawling bush up to 10 feet tall but spreading as far as 15 feet. Red orchid bush grows best in neutral to slightly acidic soils that are well drained. It loses leaves at temperatures near 20°F, but recovery is quick.

There are more to consider for the future. The rare blue flowered Bauhinia grandidieri, the stately B. petersonii, the rugged B. ramosissima and various unnamed mauve to purple flowering forms from eastern Mexico, it goes on and on. I can’t wait to try them all.

Mary Irish is a freelance writer, book author and speaker in Castroville, Texas. She’s the former director of horticulture at the Desert Botanical Garden in Phoenix and currently works at the San Antonio Botanical Garden.