These are fantastic native trees. They should be more popular than mesquites because they are much better trees and much prettier. Their warm season flushes of yellow blooms are breathtaking, and they are extremely forgiving.
I suppose they are all in the genus Parkinsonia now, but since the nursery trade is always a decade or two behind in nomenclature, I am sticking to what they have been called for years, Cercidium (with two exceptions below).
In Tucson they are all hardy enough. Palo Brea probably being the least hardy (to low 20s F). Most take temperatures between 5 and 15 degrees F.
Palo verdes are moderately messy when pods drop. I actually like the floral litter after a good bloom. I contend that floral litter is an undervalued ornamental quality. But I guess I am not so hell bent on raking up my yard.
Watering depends on the season and how long you have had your plant. Water often to get established, and not unlike all plants I mention, mulch well. Even though palo verdes can tolerate lots of conditions, they will benefit from a nice mulch layer and will need to be watered a LOT less.
Established plants need water about once every 1-2 weeks in summer, about once a month or so in winter. Desert trees are often pushed too fast to grow and have weak growth as a consequence. The blue palo verde can suffer such problems. Plant in full sun.
Some plants can be a tad weedy. Blue palo verde is moderately weedy, and Mexican palo verde is extremely weedy. Chilean palo verde can sucker profusely.
The palo verde beetle and mistletoe are two pests that bother palo verdes, but trees don’t normally succumb to these problems unless they are already compromised. Take good care of your trees and you won’t need to worry about such things.
Here is a breakdown of the individual species:
This one is perhaps the largest species. They can grow to about 25 to 30 feet tall. The canopy is much denser than most species and as the name denotes, the tree almost has a blue tinge to it (though it takes a creative eye to see that). The trunks on older trees will eventually lose their green hue and become “barky” and brown. Native to washes and slightly wetter locations even though very drought tolerant. The amazing bright yellow flower display can be witnessed between March and April and may remind you of a Monet painting.
This is the smallest of the palo verdes. It almost should be considered a shrub. Mature plants can get to about 15 feet tall, but usually seen at about 8-10 feet tall. It grows on the drier areas, as the name suggests, like on rocky outcrops. The trunk is very beautiful, and usually stays green with brownish striations and somewhat more gnarled-looking. The bloom season is from April to May, with slightly more pale yellow flowers than the blue palo verde.
This gorgeous tree can get 20-30 feet tall, and also keeps its green trunk as it ages. The Argentine variety is much hardier than the Sonoran variety. Most in the trade seem to be the Argentine, but most nursery people probably aren’t sure what stock they have. Palo Brea grows from Mexico to South America. Bright yellow flowers occur March through May.
This complex hybrid was developed by Mark Dimmitt at the Arizona-Sonora Desert Museum. The plant is the result of hybridizing between Cercidium microphyllum and Parkinsonia aculeata, then with Cercidium floridum. It has the larger orchid-like, attractive flowers of the Mexican palo verde but lacking the messiness and weediness of that species. The gorgeous flowers can be seen in late spring and can keep blooming throughout the warm season.
This natural hybrid from Sonora is a rare find, but worth the hunt. Blooming in mid spring, it looks much like Palo Brea but being darker green in hue.
This tree won’t need planting. It will plant itself. I don’t suggest planting it on purpose because it is incredibly messy with it’s foliage midribs and pods. It also doesn’t tend to live long. However, if you have one already in the yard, and you can manage the mess, it is a nice bloomer in late spring into summer. Very weedy. It will come up on it’s own all over your garden; in your pots, in your flower beds, vegetable garden, in among other landscape plants…it’s a bit of a pain in the ass.
If you can manage to find this plant (it is sometimes available at botanical garden sales, grab it. Bite and scratch anyone who tried to take your plant. It’s a cool one–In Tucson see sales at Tohono Chul, Desert Survivors, Tucson Botanical Gardens, or at the Boyce Thompson Arboretum in Superior, Arizona). This one grows to about 20-25 feet tall. The trunk has a peeling, mottled, eucalyptus-looking veneer. This one blooms before the others in early spring. Plants can sometimes sucker to form a grove. Prune suckers if this is not wished. Totally hardy in Tucson, this plant is found in some parts of its natural distribution growing in layers of salt which would kill most normal trees. However, it doesn’t need such conditions to grow.
Purchase palo verdes in Tucson at nurseries like Mesquite Valley Growers, Desert Survivors, and hit up (as mentioned in the chapters above) at plant sales put on by the various botanical gardens and parks about town.