Parkinsonia florida aka Blue Paloverde

Parkinsonia florida, or blue palo verde, belongs to the pea family, Fabaceae. Its older name, Cercidium floridum, remains a synonym. Its native range spans southeastern California, Arizona, and northern Mexico. It grows in desert and dry shrubland habitats. In this range, it often grows in desert washes. It is also the state tree of Arizona.

This small tree can also form a large shrub. It often has several stems and a crooked trunk. Many fine branches form a broad, spreading crown. Garden trees reach about 25 feet [7.6 metres] tall. Some trees reach 50 feet [15.2 metres], well above that usual size. Virginia Tech describes trees reaching 30 feet [9.1 metres]. The tree sheds its leaves during dry periods. It stands bare of leaves for much of the year.

Young bark is smooth, thin, and blue-green. Older bark turns light brown and becomes somewhat scaly. The green bark on branches carries out photosynthesis. Slender, smooth twigs bear short, stiff spines at leaf bases. The small, blue-green leaves grow in an alternate pattern. Sources describe their compound structure as pinnate or bipinnate. Leaves often have just two leaflets, though some have more. They last only a short time. Oregon State notes that leaves appear after summer rains.

Bright yellow flowers open in spring and early summer. They grow in clusters and have five petals. Oregon State notes red spots on the upper petal. Sources give flower widths of about half to three-quarter inch. The fruit is a flat legume, or seed pod. Pods turn straw-colored to light brown as they ripen. They measure about 1.6–4 inches long and hold one to eight flat seeds. Virginia Tech notes that pods ripen in summer and soon fall.

Grow blue palo verde in full sun and well-drained soil. Once established, it needs little or no added water. Oregon State places its cold hardiness at USDA Zone 8b. Its broad crown and yellow flowers give it landscape value. The blue-green branches remain a feature when leaves are absent. Spines are another clear feature to consider when choosing its site. The supplied sources give no specific pest or disease guidance. They also do not establish food uses or toxicity.