Mexican Palo Verde
Parkinsonia aculeate - Linnaeus
Fabaceae (bean) family
Jerusalem Thorn is a small tree growing to 25 feet tall with a short trunk and a graceful, spreading, sometimes weeping, crown. The slender branches and twigs have green bark, and are armed with stout spines up to 1 inch long. Its preferred habitat is open grasslands, canyons, or as an ornamental in tropical and subtropical gardens. Distribution in the Escambia region is strictly as an ornamental that will persists long after a homestead has been abandoned, and in places like cemeteries and rocky embankments where maintenance is not commonly needed..
The leaves are strap-like, twice compound arranged in long feathery streamers. Each leaf is modified into 2 or 4 strips that may be 10 to 16 inches long and about 1 inch wide. Each strip has 22 to 23 pairs of tiny opposing leaflets. The leaves usually appear shortly after a rain, folding up at night. Within a few days after emerging the tiny leaflets fall off, leaving the persistent rachises (midribs) to flutter like streamers in the wind.
The flowers are pea-like, yellow and clustered. The first flowers appear in spring making the whole tree look like a giant yellow bouquet. The flowers are bisexual in nature and symmetrical in form. Flowers occur mostly in the summer.
The brown pods are about 3-4 in (7.6-10.2 cm) long and constricted between the seeds. Fruit comes in two forms within the same pod. About 25% of the seeds germinate readily. The remaining seeds have hard coats which must be scarified before they will germinate.