Are you familiar with the Palo Verde tree? These magnificent trees are a common sight in the Southwest, particularly the foothill, yellow, or little leaf Palo Verde (Parkinsonia aculeata) and the blue Palo Verde (Parkinsonia florida). The name “Palo Verde” comes from Spanish, meaning “green wood” or “green stick,” which perfectly describes the tree’s greenish branches and trunk. The different common names refer to their location, bark color, or leaf size.
A Closer Look
Both species of Palo Verde are spiny, green, deciduous trees with multiple trunks. The foothill Palo Verdes reach a height of about 20 feet and have yellowish bark and duller yellow/white flowers. On the other hand, the blue Palo Verde can grow up to 40 feet tall. Their twigs, young branches, and leaves have a beautiful bluish-green hue, and the leaves of the blue Palo Verde are larger than those of the foothill variety. Both species have double pinnate leaves, with the foothill species having more abundant leaves growing on longer stems.
The pods of these trees contain seeds, ranging from one to eight, although one is much more common than eight. The foothill species has pods with narrow waists between the seeds, which are about the size of lentils. The seeds of the blue Palo Verde are slightly larger and flatter, with thicker and harder shells.
Habits and Habitats
The blue Palo Verde primarily grows in washes, requiring more water than the foothill species, which is commonly found in uplands. The blue species prefers fine soils, while the foothill species thrives in coarser soils. Foothill Palo Verdes are known for their longevity, often living for over 100 years and sometimes reaching up to 400 years. In contrast, blue Palo Verdes grow faster but have a shorter lifespan, rarely reaching the century mark.
During their short flowering seasons, both species of Palo Verde are adorned with thousands of five-petaled yellow blossoms. These vibrant flowers attract a variety of pollinators, including beetles, flies, and social and solitary bees.
The Palo Verde trees have a unique adaptation – they can photosynthesize through their green bark. This ability is crucial for a tree that drops its leaves during the warm season and in response to fall cooling. Additionally, Palo Verdes have the ability to shed stems and branches during times of drought.
These magnificent trees also serve as nurse plants for saguaro cacti, providing a protective canopy that acts as a microhabitat. The Palo Verde offers warmth in winter and shade in summer for the slower-growing cactus, which will eventually replace its once-protective companion.
Palo Verdes play a vital role in supporting various wildlife. Bighorn sheep, mule deer, feral burros, jackrabbits, and other small mammals browse on their foliage. The abundant branches of these trees are also popular for foraging, perching, and nesting among numerous bird species.
Range
You can find the blue Palo Verde across the Sonoran desert, stretching from central and southwestern Arizona into southeastern California and south into western Sonora, Mexico. There are also separated populations in northern Sinaloa and Baja California. Foothills Palo Verde grows through central and southwestern Arizona and extends south into Sonora, Mexico, and Baja California.
Fun Fact: The first botanist to collect and study these remarkable trees was Irish botanist Thomas Coulter. He obtained specimens near Hermosillo, Sonora in 1830.
Keep in mind that the larvae of Palo Verde root borers (Derobrachus geminatus) feed on these trees. These larvae can grow up to five inches in length, while the adults reach up to three and a half inches with long antennae.
Now that you’ve learned a bit about the captivating Palo Verde tree, why not sign up for the DesertUSA Newsletter? It’s filled with articles on hiking, camping, exploring, wildlife, wildflower reports, and plant information. Let’s stay connected and explore the wonders of the desert together!
This article was authored by David B. Williams.
