When people think of the Sonoran desert, hillsides studded with saguaro cactus and cholla often come to mind. But interspersed between the cactus, you will find the iconic palo verde trees with their beautiful green trunks and branches.
The word "Palo Verde" means "green stick" in Spanish, referring to their green trunk, which is actually a survival mechanism in response to drought.
Palo verde trees are "drought deciduous", which means that they will drop their leaves in response to a drought situation. Their green trunks and branches are able to carry on photosynthesis, even in the absence of leaves.
Palo verde trees act as a "nurse plant" to young saguaro cacti by protecting them from the cold in the winter and from the intense sun in the summer. Beautiful, yellow flowers are produced in the spring.
There are three species of palo verde that are native to the desert Southwest; blue palo verde (Parkinsonia florida), formerly (Cercidium floridum), foothill palo verde (Parkinsonia microphylla), formerly (Cercidium microphyllum) and 'Desert Museum' palo verde (Parkinsonia x 'Desert Museum')
Another species of palo verde that are prevalent in the landscape are called palo brea (Parkinsonia praecox), formerly (Cercidium praecox). They have a dusty green trunk and branches that twist and turn. Their cold hardiness range is around 15 to 20 degrees F.
PALO VERDE USES: Palo verde trees serve as wonderful specimen trees where their green trunks, branch structure and flowers serve as a wonderful focal point in the landscape. They are drought tolerant, once established and provide nice filtered shade year-round.
When deciding where to place your tree, be sure to take into account that they need a lot of room to grow, mature sizes are listed below.
Palo Verdes don't do well when planted in grass and will decline over time. Locate away from swimming pools due to flower litter in the spring.
Because of their larger thorns and branching tendency to point downwards, palo brea trees aren't recommended in areas close to foot traffic.
Blue Palo Verde - 30 ft x 30 ft
'Desert Museum' Palo Verde - 30 ft high x 40 ft wide
Palo Brea - 30 ft x 25 ft
Foothills Palo Verde - 20 ft x 20 ft
As with many desert trees, Palo Verde trees have thorns, except for the 'Desert Museum' Palo Verde.
PALO VERDE MAINTENANCE: Prune to elevate the canopy and maintain good structure. Avoid hedging and "topping" trees as this stimulates excess, weak growth.
MY FAVORITE: As a landscape manager, horticulturist and arborist, I have grown and maintained all of the palo verde species mentioned and I truly enjoy them all. However, at home I have 4 'Desert Museum' trees. In comparison to the other species, their trunks are a deeper green, they produce larger flowers, are thornless and grow very quickly. In addition, they require little, if any, tree staking when planted.
For information on other drought tolerant trees, as well as shrubs, perennials, and ground covers, I recommend checking out Mary Irish's book, Arizona Gardener's Guide.