Tree
Mexican Palo Verde
Parkinsonia aculeata · Fabaceae
Also called: Jerusalem Thorn, Retama, Palo Verde, Horsebean
Mexican Palo Verde (Parkinsonia aculeata) is a low-water tree well suited to Tucson and the low desert. It grows to 15-30 ft H x 15-30 ft W in full sun, with a fast growth rate.
Mexican Palo Verde at a glance
- Water use
- Low (established)
- Sun
- Full sun
- Mature size
- 15-30 ft H x 15-30 ft W
- Growth rate
- Fast
- Bloom
- Yellow (often with one orange-spotted petal), Spring into summer (April-June), with sporadic reblooming after rains.
- Cold hardiness
- Hardy to about 15 F (top growth damaged in hard freezes); USDA zones 8-11.
- Soil
- Very adaptable; tolerates poor, rocky, saline, and alkaline soils and seasonal flooding better than other palo verdes, but needs reasonable drainage in cultivation.
- Native range
- Native to the Americas, ranging from the southwestern US (including parts of Arizona/Texas) south through Mexico into South America; in the low desert it is largely naturalized/introduced and considered weedy or invasive in some regions. Not endemic to the Sonoran Desert proper.
- Best used as
- Quick shade/screen, Reclamation and tough sites, Specimen where weediness is acceptable
- Wildlife
- Flowers attract bees and other pollinators; seeds eaten by wildlife; dense canopy provides cover, but prolific seeding can create unwanted volunteers.
- Toxicity
- Not considered seriously toxic to humans; thorns are the main hazard. Generally regarded as non-toxic to livestock and pets.
How to grow Mexican Palo Verde in Tucson & the low desert
Watering
Drought tolerant once established; in Tucson, occasional deep summer irrigation keeps it looking better, but it survives on little water. Tolerates more water than other palo verdes, including periodic wet soils.
Fertilizer & nutrients
No fertilizer needed; nitrogen-fixing legume. Fertilizing only encourages excessive, weak growth.
Pruning & care
Prune to remove low and excessive growth and to thin the dense, weeping canopy; train to a single or multiple trunks when young. Be cautious of sharp thorns on twigs and at leaf bases; structural pruning improves an otherwise scraggly, twiggy form.
Notes
Distinguished by long, whip-like green photosynthetic branchlets with very small, quickly deciduous leaflets and conspicuous sharp thorns. Fast and tough but short-lived, brittle, messy with seedpods, and considered invasive/weedy in parts of Arizona and elsewhere; the sterile 'Desert Museum' hybrid is usually preferred over it for landscapes. Self-sows readily.
Sources: University of Arizona Cooperative Extension; Arizona-Sonora Desert Museum; AMWUA Landscape Plants for the Arizona Desert; USDA PLANTS Database