Tree
Chilean Mesquite
Prosopis chilensis · Fabaceae
Also called: Thornless Chilean Mesquite, South American Mesquite, Algarrobo
Chilean Mesquite (Prosopis chilensis) is a very low-water tree well suited to Tucson and the low desert. It grows to 30-40 ft H x 30-40 ft W in full sun, with a fast growth rate.
Chilean Mesquite at a glance
- Water use
- Very Low (established)
- Sun
- Full sun
- Mature size
- 30-40 ft H x 30-40 ft W
- Growth rate
- Fast
- Bloom
- Creamy yellow / pale greenish-yellow, Spring (April-May), sometimes sporadically through summer
- Cold hardiness
- Hardy to about 0-15 F; USDA zones 8-11. May suffer tip dieback in hard Tucson freezes but recovers.
- Soil
- Tolerates a wide range of soils including poor, rocky, and alkaline soils; requires good drainage. Not fussy.
- Native range
- Native to arid regions of South America (Chile, Peru, Argentina, Bolivia). Widely planted (often as hybrids with P. alba/P. velutina) in low-desert Arizona landscapes.
- Best used as
- Fast-growing shade and patio tree, Streets, parking lots, and large commercial/residential landscapes, Filtered-shade specimen for dry or oasis-style designs
- Wildlife
- Flowers provide nectar/pollen for bees and other pollinators; pods and seeds are eaten by birds and mammals. Canopy offers bird nesting and roosting cover.
- Toxicity
- Not toxic to humans; pods are edible/forage. Thorny seedlings/forms can injure; many nursery selections are sold as 'thornless.'
How to grow Chilean Mesquite in Tucson & the low desert
Watering
Very drought tolerant once established; deep, infrequent irrigation (every 3-4 weeks in summer) is sufficient and preferred. Avoid frequent shallow watering and over-irrigation, which drive fast top growth, weak wood, shallow roots, and increased blow-over risk in monsoon storms.
Fertilizer & nutrients
Rarely needed; nitrogen-fixing legume. Excess fertilizer and water cause excessively rank, weak growth. If desired, one light spring feeding is plenty.
Pruning & care
Prune in late spring or early summer to establish strong scaffold branches and a balanced canopy; thin the crown before monsoon season to reduce wind resistance and limb breakage. Train to a single or multi-trunk form when young; do not over-thin (lion-tailing weakens limbs).
Notes
One of the most common landscape mesquites in Tucson/Phoenix because of its fast growth, dense filtered shade, and (in selected clones) near-thornless habit. Most 'Chilean mesquite' in the trade are hybrid seedlings, so form varies. Main drawbacks: shallow aggressive roots and weak wood prone to monsoon wind throw if over-watered. It can self-seed and is regionally weedy near washes.
Sources: AMWUA "Landscape Plants for the Arizona Desert"; Water Use It Wisely; Arizona State University (C. Martin plant library); University of Arizona Cooperative Extension