One of the best shade trees for the desert Southwest is the Chilean Mesquite. I live in Southern Arizona and like the tree for three reasons. It is easy care. Truth be told, if the tree has had a good start, it can basically survive and grow with little to no assistance. It does not require a lot of water (great for Arizona!), it can live in the desert soil and thrive on the local rain water, and you can fertilize once a year in the spring with a slow release tree and shrub food. I know people with beautiful Chileans who have done nothing since having theirs planted. Not saying you necessarily want to do that, but it is rather low maintenance. Its fast growth gives you a wonderful source of shade with a fine umbrella. I would definitely water (for the first year, seven to ten-day intervals) and feed a young Chilean Mesquite once in the spring.
My Chilean Mesquite has pretty good-sized sharp thorns. You want to wear gloves when pruning – especially when picking up suckers and branches. The tree grows to 30 to 35 feet tall with an average 35 foot umbrella.
I am giving you, now, a personal observation. I am not sure this is something an etymologist or agronomist would even offer, but it is an honest note for this neck of the woods. These mesquites can be an attraction to bee swarms – Palo Verde even more so. You don’t need to fear this, but I suggest that you simply look your tree over before working on or around it. Most of the time you can hear the humming. I suppose one could say this is true of any plant in Southern Arizona, really. But I have had a little bad luck with a swarm deciding to land on the trunk – perhaps waiting to continue, perhaps thinking it might be a possible new home. In one case, the swarm disappeared. In another, I had to call an insect outfit who deemed it necessary to cut them because I had small children who might be in and out of my back yard. However, I have lived in Arizona for 60 years and would not give up the delightful shade these trees provide. The Africanized bees have not been here that long, and two times is not horrendous. And, this variety of mesquite is all over the place in the area, as they are very popular because of their beauty and ease of maintenance.
Another interesting aside is that there is also a mesquite that is a hybrid of the Argentine Mesquite (Prosopis alba ) and the Chilean. I am told that there is a hybrid mesquite also that has no thorns, but have not seen that. I suppose it would be referred top as a thorn-less mesquite, but am not sure.
The local Arizona varieties of mesquite, grow into wonderful shade trees also at about the same dimensions. Their adaptation is perhaps even better than the Chilean for Arizona.
Types of Arizona Mesquite:
Prosopis glandulosa – known as the honey mesquite or Texas Mesquite. These usually have a weeping form, and can be quite pretty.
Prosopis velutina – known as the Arizona mesquite or native mesquite. Also called the velvet mesquite because of the soft hairs that cover young growth. They are rather shaggy and snarled in appearance. They are popular in nurseries, and will grow well on lawns and golf courses.
Prosopis pubescens – known as the screwbean mesquite, earning its name from the spiraled or coiled shape of their seed pods.
If considering the development of a natural shade garden, I would certainly choose a mesquite, finely trimmed to add to the garden. Arizona nurseries can fill you in on more details about the desert mesquite tree. My smallest Chilean mesquite grew from a maverick seed. I transplanted it from my front yard to my backyard when just a baby. The transplant easily. And, as previously mentioned, it is one of the fastest growing trees.
To my way of thinking, the Chilean has a slightly different shape leaf though very similar (tiny leaves), with the leafage a much deeper green. I judge the thorns slightly longer and thinner with a red tinge to the wood. The Arizona mesquite has a tan to grey wood and somewhat thicker thorns.