Scientific: Prosopis alba
Common: South American mesquite, Argentine mesquite, algarrobo blanco, algarrobo panta
Family: Fabaceae (Leguminosae)
Origin: Arid and subtropical regions of South America; Bolivia, Peru, Argentina, and Paraguay. It has naturalized in Hawaii.

Pronounciation: Pro-SO-pis AL-ba

Hardiness zones
12-13, just recently grown in nurseries in southern California
USDA 9-10 (arid and semi arid regions only)

Landscape Use: Argentine mesquite is a large summer shade tree for xeric landscapes. This is not a lawn or street tree, nor is it a tree for small urban spaces!

Form & Character: Large, upright and spreading, asymmetrical form, nearly always twisting, contorted and misshapen when young with the potential of becoming picturesque with age (so long as it has been properly trained).

Growth Habit: Woody, evergreen to deciduous perennial tree, fast growing, irregularly spreading and randomly branched, 30 to 40 feet height with a spread of 80 to 100 feet, trunk rough chocolate brown w/ age, growth begins each year in May and continues through November.

Foliage/texture: Bipinnate compound leaves to 4 inches long. Young trees often have only two pinna; however, as tree specimens mature they will grow foliage with four pinna. Leaflets, in numerous pairs, are generally only 1/2 inch long. Leaves with stipular spines present or absent; when present can grow sometimes to 2 inches long and are dangerous; medium fine texture.

Important note: Foliage of P. alba is generally slightly smaller than P. chilensis.

Flowers & fruits: Flowers are greenish yellow catkins in spring, relatively inconspicuous because of color; fruits are 3 to 5 inch long twisted, beige pods, ripen in July, dehiscent, edible.

Seasonal color: None

Temperature: Hardy to 15oF

Light: Full sun

Soil: Tolerant

Watering: Drip irrigation during the first year after planting into the landscape, after which little to no supplemental irrigation is needed.

Pruning: All South American mesquite trees will require vigorous training and corrective pruning when young to establish an upright and symmetrical crown architecture.

Propagation: Seed is the historically common method; however, commercial nurseries are now propagating asexually by cuttings, air layering, and grafting. Selection and asexual propagation of superior clones (thornless, evergreen habit, symmetrical branch habit) offers the best future for this tree in local urban landscapes.

Disease and pests: Aphids on new growth in spring (it's raining honey dew on my car!). Bacterial wetwood is nearly ubiquitious on all urban trees. Also, Texas root rot if soil is excessively wet during summer.

Additional comments: Most South American mesquite in Phoenix landscapes are hybrids of P. alba and chilensis. South American hybrid mesquites are currently very popular locally and make excellent summer shade trees if cultured correctly. Always select thornless variants (such as Prosopis x 'Phoenix'TM) that are cutting grown. Superior selections such as the cultivar 'Rio Salado' are now being offered by local wholesale nurseries. In my opinion, one of the best cultivars is the 'Arizona mesquiteTM', a hybrid selection between the South American mesquite hybrids and P. velutina (native to our desert Southwest) that is sold locally by Desert Tree Farm Nursery in Phoenix.

In general, mesquite trees produce much litter throughout the year such as the obligatory undercanopy mangled carpet of seed pods in July. Young container-grown hybrid mesquite trees, less than 5 years in the landscape, can be prone to blow over during summer monsoon storms if they have girdled roots (root deformation caused by growth in nursery containers), have been heavily drip irrigated and the drip emitters are positioned close to tree trunk, or if they are planted turf as a lawn tree. Young trees should be staked securely and trained religiously to develop a central straight trunk and a strong schaffold branch architecture. Like Chilean mesquite, Argentine mesquite produces frequent crossed branches and grows water sprouts (around pruning wounds) and suckers. Much genetic variation and local hybridization with P. chilensis makes identification using only phenotypic characters difficult. The sapwood of Argentine mesquite is light yellow, while the heartwood is rich reddish brown changing to dark brown.

Mesquite is an excellent fire wood!

Note of caution: Recent over planting of mesquite trees in inappropriate locations that increase maintenance demands may lead to negative public perceptions of this tree in the future. Foliar contact may cause skin rashes. South American mesquite will grow large lateral roots that will remain near the surface of urban landscapes because of landscape irrigation.