Genus and Family: The genus, Tabebuia is native to the Amazon rain forest and other tropical parts of Mexico, and Central and South America. It included nearly 100 species of trees commonly known as trumpet trees, named so because of the shape of the flowers. In 2007, about 30 species of the trees in Tabebuia were renamed Handroanthus when molecular studies found that they were more closely related to genera other than Tabebuia.
Handroanthus can be distinguished from true Tabebuia by the minute hairs on the leaves or flowers and extremely dense wood containing copious amounts of the compound lapachol in its bark. Tabebuia is restricted to those species with white to red or rarely yellow flowers. Tabebuia and Handroanthus belong to Bignoniaceae, a family of deciduous, evergreen, and semi-evergreen trees, bushes, and vines known for their showy flowers. Jacarandas, African tulip tree, catalpas, bower vines, cape honeysuckle, and cat’s claw vines are also part of the Bignoniaceae family.
Growth: In the United States, trumpet trees are most commonly found in southern California, in some of the milder areas of northern California, parts of the southwest, and Florida. The ones most common to southern California are the Pink (or Purple) Trumpet tree, Handroanthus impetiginosus, and the Golden Trumpet tree, Handroanthus chrysostricha. Pink Trumpet trees are found throughout San Diego with some exquisite specimens in Balboa Park.
The Los Angeles County Arboretum and Botanic Garden helped to introduce trumpet trees to cultivation in the 1970s and have the best collection of mature trumpet trees in California. Lining the streets and gardens within the Walt Disney Concert Hall in downtown Los Angeles are twenty-three Pink Trumpet trees.
While pink and golden trumpet trees share many characteristics, they display differences in growth. The golden trumpet tree may grow up to 36 inches per year to heights of 15 to 25 feet, spreading 10 to 25 feet wide. Dependable and uniform in growth, the golden trumpet tree varies little in shape or color.
Pink trumpet trees grow up to 24 inches per year to a mature size 20 to 30 feet tall and 10 to 20 feet wide. Their spreading branches often droop toward the ground, and there are color variations in flowering. When grown from seed, pink trumpet trees may take anywhere from three to 24 years to flower. Unusual for a tropical tree they may live up to 300 years.
Handroanthus has a hard fissured bark and palmately compound leaves usually with five leaflets. The leaves are smooth and shiny on both surfaces. The lance-shaped leaflets are 2 – 4″ long by 1 – 2″ wide with prominent veins. Both Tabebuia and Handroanthus have a pod or pod-like elongated fruit up to one foot in length. Propagation is by seed or by vegetative methods. Vegetatively propagated trees bloom at the same time, while seed propagated trees flower at different times.
In California, trumpet trees usually drop their leaves in the winter and bloom in March and April, then push out new leaves as their flowers wane. They can also bloom at other times during the year while in the leaf. Both species benefit from the shaping and removal of the weaker and dead branches and brittle wood as the trees mature. The flowers are easily accessible to both bird and bee pollinators. There are no known serious pests or diseases that affect these trees.
Appearance: Trumpet trees are valued as ornamentals and their slow growth and spectacular flowers make them ideal patio, street, and parking lot island trees. The Pink (or Purple) Trumpet tree, H. impetiginosus is also known as Pau d’arco, pink lapacho, and ipe, and is the national tree of Paraguay.
The H. impetiginosus has showy, trumpet-shaped lavender-pink flowers with yellow throats, 2 – 3″ long by 2″ wide, and are produced in rounded clusters in early spring while the tree is deciduous. Flowers become larger and more profuse as the tree matures with heavier flowering occurring in warmer areas. Footlong hanging seed pods follow flowers and persist into winter.
There are three cultivars of H. impetiginosus: cv. “Pink Cloud, described as compact and florifierous, deep pink cv. “Raspberry,” and cv. “Paulina,” a medium pink tree that grows to 12-15 feet at maturity and blooms intermittently all year. The San Diego Street Tree Selection Guide approved the Pink Trumpet tree for use under power lines and Public View Corridors.
The Golden Trumpet tree, H. chrysotricha, has maroon-striped, golden flowers, and is less cold hardy. It is also smaller and more uniform in shape and flower color. It is the national tree of Brazil. Dependable and uniform in growth, the golden trumpet tree varies little in shape or color.
Climate, Soil, and Water Preferences: Tabebuia and Handroanthus prefer full sun but will adapt to partial shade. They tolerate heat and they can be cold hardy to freezing temperatures for brief periods. Freezing temperatures will weaken the trees. Seaside- and drought-tolerant once established, it prefers consistent moisture. Both trees do well in urban environments and don’t need fertilizer or irrigation under normal soil and weather conditions.
Timber and Medicinal Use: Handroanthus wood, commonly known as ipe (ee-pay), is one of the hardest and densest on earth and is used in the tropics for bows, boats, railroad ties, and tool handle. It is exported to the United States for flooring and decking. The wood is also insect and fungus-resistant. Because of these qualities, it has become a major cause of deforestation in the Amazon.
The bark and wood of H. impetiginosus have been long used by the South American indigenous peoples (where it is known as pau d’arco) as well as in traditional Western medicine. Lapacho, a tea made from the bark of the tree, is used for a variety of ailments and conditions. Possibly unsafe at high doses, pau d’arco is also used to treat a wide range of infections. Lapachol, the main active compound in the bark and wood of the tree, is toxic, and its strong antibiotic and disinfectant properties may be better suited for topical applications.