In 1954, the Arizona state legislature designated palo verde as the state tree. Back then, palo verde trees were in the genus Cercidium. The genus was later revised to Parkinsonia and two species, florida (blue palo verde) and microphylla (yellow or foothill palo verde), were described.
The genus, Parkinsonia, honors John Parkinson; a famous English herbalist and botanist whose career straddled the 16th and 17th centuries. The specific name florida derives from Latin for “flowery” while microphylla is Latin for small leaves. Both species are flowery in the spring and have small leaves when present.
Deep roots provide stability during flash floods and access to deep ground water in times of drought for both species. While juveniles specimens may be found growing as multi-branched shrubs, with time a single dominant trunk may develop. P. florida trees can attain heights up to 30 feet while the maximum height of P. microphylla is around 20 feet.
P. florida favor growing in washes and have a life expectancy of no more than 50 years. P. microphylla prefer rocky slopes or gravelly flats and have been known to live 200 years.
Both species are leafless for much of the year; a xerophytic adaptation that reduces transpiration, leaving green limbs to conduct photosynthesis. The green branches give rise to the common name “palo verde,” Spanish for “green stick.” Blue palo verde have a blue-green tint to their bark while the yellow palo verde bark is yellow-green.
While both species bloom profusely in the spring, P. florida tends to bloom earlier than P. microphylla. Although the predominant blossom color of both species is yellow, the yellow palo verde banner petal is white.
Bees and other insects are attracted to palo verde flowers where act as pollinators. The resulting seedpods are typically 1½ to 4 inches in length containing 2 to 7 seeds. Young pods are green in color, turn tan, and eventually sun-bleach to a near white color.
Green palo verde seedpods.
Both palo verde species play similar roles in the desert ecosystem. They provide roosts, cover, shade and food for birds, reptiles, and small and large mammals.
Native American cultures, such as the Pima and Tohono O’odham, consumed palo verde flowers, pods and seeds. The flavor of tender green P. microphylla seedpods is said to resemble that of snow peas and can be consumed raw, while P. florida seedpods are slightly bitter. They also boiled the green pods with meat to make a stew. Dry seeds were shucked from their pods, ground to make flour and then cooked to make a gruel. The description of palo verde’s food uses are not an endorsement for its consumption.
For those interested in more information on palo verde, conduct a web searches on both Parkinsonia florida and microphylla.
Close-up of a P. florida flower with an all yellow banner petal.
Green palo verde seedpods.
Field observations and photographs for this article were based in full or in part from visits to the Cienega Creek Natural Preserve. A permit is required to enter the preserve. Please visit the Cienega Creek Natural Preserve web site (http://webcms.pima.gov/cms/One.aspx?pageId=1515) to learn more about the preserve and for how to obtain a permit.
