Whether up-lit to produce dramatic silhouette on walls and hardscapes, exploding with bright yellow spring flowers or adding a rich sculptural quality, Palo Brea (Cercidium praecox) brings beauty and desert elegance to the landscape. It is one of the most popular and sought after trees in the arid landscape palette. This popularity is based on the tree's unique natural beauty, displays of bright yellow flowers, smooth green trunks and gracefully interwoven branches. Their strong visual impact makes them ideal as a theme tree for streetscape plantings, as accent trees and as individual specimens in entry monuments or at the focal point of a landscape. With their distinctive visual qualities they can bring a strong unifying look to landscape and are often used as the theme or dominant tree in large commercial designs and street plantings.

Palo Brea, also called Sonoran Palo Verde has a very distinct appearance relative to other desert natives. It combines both lush, vibrant green with a classic desert form and leaf canopy. Its natural habitat is the desert plains from southern Sonora and Baja California, Mexico, to Venezuela and Peru. It is not native to the American southwest but blends almost seamlessly with indigenous Palo Verdes, including both Blue and Foothill Palo Verde. This arid yet lush appearance makes it a highly adaptable tree for uses in both very urban landscapes and in designs intended to reflect native desert scenes.

Trees grow at a rate comparable to Blue Palo Verde and mature to a height and spread of 20 to 30 feet. They grow best in full sun and well-drained soils. Yellow funnel shaped flowers are produced in abundance in the spring with flowers sometime persisting into early summer. In years with very mild winters or warm micro-climate locations flowering may begin in late March. Small, tan, elongate pods containing one or two seeds mature by mid-summer and are generally all shed before the onset of the monsoon season. Young twigs and smaller branches are armed with small thorns. Thorns have not proven to be an impediment to using Palo Brea near sidewalks, along streetscapes, in parking lots or other pedestrian areas.

Drought tolerance is another attribute of this tree. Once trees are established and reach a desired size and height, further growth can be managed by irrigation. Specimens in landscape settings can be gradually weaned from supplemental irrigation and can subsist with little or no irrigation other than natural rainfall. Such naturalized trees grow far more slowly and, as a result, require far less pruning and maintenance. Periodic deep irrigation and the application of fertilizer, during the spring and summer months, will enhance lush growth and maximize spring floral displays. Trees maintained under these conditions may require additional, seasonal pruning.

The open branching and dispersed leaf canopy produces diffuse shade that allows under-story plants to flower and thrive and won’t inhibit the growth of surrounding turf. Care must be exercised in the selection of under-story plants or the placement of Pale Brea in turf area. This tree can be severely damaged or killed by over irrigation or excessive water runoff from rainfall, when planted in poorly drained soil conditions. Further, the application of fertilizer and winter irrigation of under-story plants or turf can increase the susceptibility of Palo Brea to freeze damage.

Published studies of Palo Brea planted in landscapes indicate that it is hardy to about 20 degrees F. In such settings they survive typical winter conditions in the Tucson, Phoenix and Palm Desert, CA areas with little or no freeze damage. When growing in containers or boxes, above ground, trees appear more prone to frost injury, over watering, and winter transplant shock. Nursery boxed Palo Breas may be injured anytime winter temperatures drop below 28 degrees F. Dormant, boxed Palo Breas may appear normal during the winter months following injury. In the Spring when temperatures stimulate bud break, evidence of injury (brown discoloration of the branches and/or trunk leading to
cracking and splitting of the bark) appears on damaged trees.

Palo Brea, like all plants grown from seed, have a built-in level of genetic diversity that shows up as varying levels of cold hardiness. The hardiness of Palo Brea is also influenced by the maturity of the tree, duration and intensity of low temperature, heat retention provided by other plants, and the proximity of building and streets. Transplant shock associated with unusually cold weather may also play a role in winter losses of Palo Breas. Loading, shipping, unloading and planting puts stress on all trees. Under non-winter conditions, arid region trees recover rapidly and resume growing. In winter some Palo Breas do not recover from these stresses as they would during their growing seasons.

Growers are continually searching for Palo Breas that exhibit superior cold hardiness. Several have been identified and are currently being propagated vegetatively. Efforts to identify greater cold hardiness has also led to the evaluation and selection process of specimens that have longer and more intense blooming periods. At present these clones are in somewhat limited supply. Developing propagation methods for our unique southwestern trees is a slow and tedious task, under evaluation every new season and optimistically formulating higher success rates with each new occasion.

Palo Brea is considered by some authors to be the most beautiful tree in the desert palette. Its remarkable combination of sculptural elegance, lush green appearance and spectacular flower display make it among the most coveted desert adapted landscape tree. It is likely that demand for this tree will continue to increase as more landscape architects and designers become familiar with this remarkable tree.