Scientific: Prosopis chilensis - note that in the image captured by C. Martin in April that in the background is Prosopis alba.
Common: Chilean mesquite, South American mesquite
Family: Fabaceae (Leguminosae)
Origin: South America

Pronounciation: Pro-SO-pis chi-LEN-sis

Hardiness zones:
Sunset 12-13
USDA 9-11 (arid and semi arid regions only)

Landscape Use: Summer shade tree for dry or oasis landscapes of all types, parking lots, large landscape medians.

Form & Character: Upright and spreading, develops a broadly umbrella-shaped form when mature that is more symmetrical than Prosopis alba. Though Chilean mesquite has a symmetrical form, it's inner crown branch topology is chaotic, rugged trunk and crown character.

Growth Habit: Chilean mesquite is a semi-evergreen, woody perennial tree. It's rate of growth is strongly depended on water availability. If water is available then the shoot growth rate is rapid. Well-watered trees can exceed 50 feet in height with a much greater spread (up to 100 feet in diameter). In Phoenix, Chilean mesquite remains semi-dormant each year from December to April.

Foliage/texture: Chilean mesquite has bipinnate compound leaves that are 4 to 6 inches long. Numerous pairs of leaflets range from 1/2 to 1 inch in length. At the base of leaves are a pair of variably dangerous stipular spines that range in length from non-existant to 3 inches long. Foliage of Chilean mesquite is typically larger than P. alba.

Flowers & fruits: Greenish yellow flowers in 2 inches long catkins in April; fruit an elongated and slightly twisted light brown pod, ripens in July, dihiscent.

Seasonal color: None

Temperature: Highly tolerant of desert heat. Injured by temperatures below 20oF.

Light: Full sun, no shade.

Soil: Highly tolerant of Sonoran Desert soil conditions. In fact, Chilean mesquite performs best in native, unamended desert soil.

Watering: None to occasional summer irrigations to encourage vigor only if needed. DO NOT irrigate regularly as this will cause the tree to grow structurally weak wood. Chilean mesquite is NOT a lawn tree.

Pruning: Prune rigorously when young to train a strong and limited schaffold branch system. Otherwise crown raise and thin mature mesquite trees to improve under canopy access, remove occasional suckers and water sprouts, and decrease wind resistance to reduce risk of wind thrown in irrigated sites.

Propagation: Seed, acid scarification; air layering and stem cutting propagation is difficult.

Disease and pests: Bacterial wet wood

Additional comments: South American mesquites are popular because of their rapid growth, apparent lower water requirement and strong shading potential, but beware of their aggressive spreading habit. They have much genetic variation. In addition, will readily hybridize with P. alba and many of the newer nursery selections are superior hybrid crosses between these two species. There's a growing body of anecdotal evidence to suggest that contact with mesquite foliage and pollen may cause allergies.