Scientific: Parkinsonia aculeata
Common: Jerusalem thorn or Mexican palo verde
Family: Fabaceae (Leguminosae)
Origin: Mexico

Pronounciation: Par-kin-SONE-ee-a a-cu-lee-A-ta

Hardiness zones:
Sunset 11-24
USDA 9-11

Landscape Use: Mexican palo verde is a rarely used, but oft found arid-zone urban tree in Phoenix. This tree epitomizes what is meant to be a garbage or trash tree. Its best use is as a light shade tree in the most difficult and neglected urban desert sites. It is also sometimes used by the Arizona nursery trade in hybridization works with other Parkinsonia species to produce cultivated varieties of superior form and texture, or it is sometimes used as a rootstock for other far more superior Parkinsonia scion selections.....beware of rootstock eipcormic shoots!!

Form & Character: Open and asymmetrical, wispy, very stiff and slightly pendulous, green.

Growth Habit: Vigorous growth from seed to 35 feet with equal spread 'in almost no time'. This aggressive tree will usually produce copious numbers of 'water sprouts' (epicormic shoots) each year, especially if around sources of soil water.

Foliage/texture: Mostly deciduous (persistant long rachis with no leaflets), especially during dry periods; pinnately compound leaves to 6 inches long, many pairs of tiny ephemeral leaflets to 1/8 inch long, persistent, short, paired, wickedly hooked stipular spines exist at each leaf node, stems and branches photosynthetically green like other Parkinsonia taxa; medium fine texture.

Flowers & fruits: Usually flowers heavily in May by producing yellow pea flowers with a distinct orange red marking. Also flowers sometimes sporadic during summer and early fall. Fruit are dark brown pods with pointed sharp ends, seed blackish brown with hard coat. Heavy fruit set in summer with fruit drop in July.

Seasonal color: Heavy yellow flower set in May.

Temperature: Tolerant of cold, heat loving....in sum, Mexican palo verde loves Phoenix!

Light: Full sun

Soil: Highly tolerant of all but damp soils.

Watering: None once established. Irrigation will promote spring and early summer trunk suckering

Pruning: Elevate canopy base and remove trunk suckers in late spring, stake vigorously young trees. Best if trained into an inverted vase form. Be forewarned though.....this trash tree will hurt you if you are not properly attired. Mexican palo verde prunage shreds difficultly in a chipper.

Propagation: Seed, naturalizes easily in Phoenix. Seed germinate readily in the landscape in gravel rocked (natural mechanical seed coat scarification) landscapes just after the summer monsoon rains. Otherwise, propagate seed rapidly anytime by scarifying in 95% sulfuric acid for 30 minutes followed by a one hour rinse in cool tap water. It is also used as a rootstock (be viligant to prune any basal rootstock suckers) for scion of Parkinsonia hybrids.

Disease and pests: Sadly, there are no diseases and pests of consequence that are able to stifle the natural proliferation of this tree in the Phoenix area.

Additional comments: Jerusalem thorn is invasive! It will readily naturalize in Phoenix urban landscapes and urban open spaces including vacant lots, flood control channels, railroad right-of-ways,and other local dry riparian washes. Its wood is very brittle and branches are easily broken by high summer monsoon winds. Be sure to wear gloves when pruning as tips of stipular spines readily break off and infect skin. Leaf rachis and fruit pods are a source of much landscape litter. I don't recommend this tree for use in Phoenix landscapes as there are many other superior Parkinsonia selections that are commonly grown by local Arizona wholesale nurseries.

Ending on a positive note: The genus Parkinsonia is derived from John Parkinson who was a British Botanist and herbalist under King James I. The species name aculeata means "having prickles" (how aptly named). Jerusalem is a corruption of Spanish girasol, meaning turning toward the sun.