Arizona Highways Online
Paloverde Tree - Cercidium floridum (blue), Cercidium microphyllum (yellow) and Cercidium praecox (Sonoran)
By Kathryn Eastlick
If you drive through Arizona during March or April, you will doubtless notice
green trees draped in thousands of bright yellow blossoms. In the city, wind plucks the blossoms off their branches and sprinkles them along streets like confetti, giving commuters a colorful drive home. As Arizona’s state tree, the paloverde serves as a testament to desert beauty and the adaptive skills necessary to thrive in such a harsh climate.
In Arizona, three species of paloverde trees flourish – the yellow paloverde, blue paloverde, and Sonoran paloverde (also called Palo brea). Yellow paloverdes reach about 20 feet in height and have yellowish bark and pale yellow blossoms. Blue paloverdes, which grow primarily along washes, can reach 40 feet and have bluish-green bark and bright yellow flowers. Although the blue paloverde is taller, it also requires more water than its yellow brother and will die sooner, usually before its 100th birthday. Yellow paloverdes enjoy coarse soil found in the uplands and almost always reach their centennial birthday - some have even lived 400 years.
The Sonoran paloverde is probably the most popular of the three species and can often be found decorating front yards and city sidewalks. Although the Sonoran paloverde doesn’t tolerate cold weather as well as the other species, its lime green branches, lush leaf growth and symmetrical canopy prove irresistible to landscapers.
The most remarkable feature of paloverde trees is their ability to photosynthesize even when leafless. To combat drought and survive extreme temperatures, paloverdes drop their leaves, and sometimes their stems and branches. Through their distinctive green branches and trunk, paloverdes (Spanish for "green stick") can still carry on photosynthesis. The thin green bark carries chlorophyll-bearing tissue, which absorbs the sunlight and converts water and carbon dioxide into oxygen and glucose, which it uses as food.
Paloverde trees also serve as desert nursemaids for baby saguaros. As a saguaro cacti begins its long journey to adulthood (saguaros grow about an inch per year), paloverdes provide a protective canopy, which gives the cactus warmth in the winter and shade in the summer. The canopy also hides young saguaros from animals that might eat and destroy them.
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