The Arizona state tree is the Palo Verde. Palo Verde is Spanish for "green pole" or "green stick.", and refers to the tree's greenish branches and trunk. The spelling of the tree's common name varies from "paloverde" to "palo verde", but "palo verde" is the most common.
Arizona became a state in 1912 but the Arizona state tree was officially adopted in 1954, introduced to the Twenty-first Legislature of Arizona by 11 different women residing in six different Arizona counties. It's interesting to note that the legislation that adopted the palo verde tree did not specify a particular variety. The Arizona Revised Statutes, Title 41, Chapter 4.1, Article 5, Section 41-856 is titled "State tree" and simply states that "The Palo Verde (genera cercidium) shall be the state tree."
Two Palo Verde species are native to Arizona. The Cercidium floridum has blue-green branches and leaves, and is commonly referred to as the Blue Palo Verde. The Cercidium microphyllum has yellow-green branches and leaves, and is commonly referred to as the Yellow or Foothill Palo Verde. Both species of palo verde are spiny, multi-trunked, deciduous trees. Yellow palo verde trees reach about 20 feet in height and have more yellowish bark and duller yellow/white flowers. Blue palo verdes, on the other hand, can grow as tall as 40 feet. Their branches and leaves are bluish-green and are larger than the yellow palo verde.
Palo verde trees are flowering trees in Arizona that bloom in the spring. During their short flowering seasons, both species produce thousands of five-petaled yellow blossoms which attract various pollinating insects including bees, beetles, and even flies.
The blue palo verde tree requires the most water of the two species, and is found most often in washes and other areas with higher water availability and finer soil. The yellow palo verde tree requires less water, and is found most often in coarser soils on higher ground away from washes. Yellow palo verdes often live over 100 years and may reach up to 400 years of age, while blue palo verdes grow faster and die sooner, rarely reaching even 100 years.