I’ve been thinking a lot about what kind of trees to plant around our new house. The high desert is a tough place for trees and we will be asking a lot of ours, so I am quite excited about having found some good prospects.
We need trees that will provide a lot of shade to the south and west during the summer without blocking winter sun. According to permaculturalists, it is also best to select trees that are “multi-purpose”. That is, each tree should be performing at least two functions. So each tree might provide not only shade, but also produce fruit, attract wildlife, act as a windbreak, and so on.
Our site is high desert so we need plants that are more cold-hardy than what we see around Tucson. Our site is also a little drier and windier than Tucson, and we don’t have a well (yet), so drought-tolerant vegetation is an absolute must. A fair amount of irrigation will be with greywater, so our trees need to be able to tolerate the increased alkalinity and salts that come from detergents. Mesquite and palo verde are perhaps the best adapted to these conditions, but wifey and I are both highly allergic to them… and the wind will blow any pollen from the trees straight toward the house. So we need trees with low pollen.
With all those requirements, it’s a wonder that there are any trees to fit the bill! Well, I found a few that should work very well.
First there is Pistacia chinensis, or Chinese pistache. It’s not the same as the cultivated pistacio, but larger and hardier. It would make a lovely shade tree (it can reach fifty feet), provides beautiful fall color, tolerates greywater, and generates low pollen. Because of its size, it needn’t be planted close by. Its canopy may exceed thirty feet in diameter, so it will shade the house in the afternoon hours yet still remain far enough away that we could plan a small addition on the west side.
Next is Punica granatum, the pomegranate, perhaps the toughest fruit tree on the planet. While relatively small trees, only reaching 12-15′ in height, pomegranates are deciduous and are good candidates for shading the south yard. This would create a cooler microclimate in the summer but still allow the sun through to the house in winter. They produce pretty tasty fruit, require little supplemental water (and then only for fruit production), and are tough as nails.
I’m also intrigued by Ziziphus jujuba, the Chinese jujube tree. It produces fruit that is similar to dates. It is drought-tolerant, takes greywater well, and is low in pollen. Fruit production is best with at least two varieties planted together for cross-pollination.
Another fruiting tree possibility is Ficus carica, the fig tree (brown turkey variety). Drought-tolerant, greywater-tolerant, deciduous, tough as nails. They can reach 20 feet in diameter for shade. I’m not sure how low-pollen they are, and the fruit drop can be messy. Probably best to put this one a little further from the house and not use it as a windbreak.
Some other possibilities for shrubby trees include Laurus nobilis (Sweet bay) and the Arizona native Dodonaea viscosa (Hop bush). These have food potential and would make good screens or windbreaks. Sweet bay is not on the UofA’s list of low-allergy trees, though hop bush is.
Now the real trick will be making sure our trees get enough water to establish themselves…