Parkinsonia microphylla (Cercidium microphyllum)Foothill Palo Verde

The Parkinsonia microphylla, commonly known as the Foothill Palo Verde and listed in tender documents as Cercidium microphyllum, is a small, densely twiggy desert tree of the Sonoran Desert with smooth yellow-green photosynthetic bark. Its minute bipinnate leaflets are shed for much of the year, leaving the green branch structure to do the work.

It is slower and stiffer in habit than the better known Blue Palo Verde, with a denser twig structure and paler cream-yellow flowers. It is used in xeriscape and desert-character planting where a small, genuinely water-thrifty tree is required.

Specifications

• Height4 to 7 metres
• Width4 to 6 metres
• Native toThe Sonoran Desert of Arizona and north western Mexico
• FoliageVery small bipinnate leaflets, shed for much of the year; the yellow-green bark photosynthesises in their place
• Growth rateSlow

Conditions

• SoilRequires sharply drained rocky, gravelly or sandy soils; intolerant of heavy or poorly drained ground
• LightFull sun
• WaterVery low; among the most water-thrifty small trees available and easily damaged by overwatering
• ClimateThrives in hot arid and semi-arid regions; tolerates frost and extreme summer heat

Additional Features

• FormSmall, densely twiggy crown with a green branch structure that reads as texture rather than mass
• BarkSmooth yellow-green photosynthetic bark on trunk and branches, holding colour year round
• FlowersCream to pale yellow pea flowers carried through late spring, heavier after winter rain
• UsesXeriscape and desert-character planting, gravel gardens, low-water medians and verges, courtyard specimens
• SpacingPlant 5 to 7 metres apart, or singly as a small specimen
• Low MaintenanceRequires no routine pruning; remove crossing branches only while the frame is forming
• Pest ResistanceLargely free of significant pests and diseases in dry climates
• Drought ToleranceExceptionally drought-tolerant, adapted to survive on desert rainfall alone once established
• Wildlife AttractionFlowers carry nectar for bees, and the dense twiggy crown gives shelter to small birds

The Foothill Palo Verde is a small desert tree for schemes where the water budget is the governing constraint.