Hot Gardens Newsletter: September 2004
Hot Footed. Fall is definitely the best time to plant in Western gardens — after all, that is when Mother Nature sows seeds. In the desert southwest, however, you should wait until the average daytime temperature drops into the 90s F. before you plant. The soil is far too warm now for the roots of transplants and, if the roots do not grow quickly, the new transplant may not survive very long. Only palms love to have “warm feet” so now is a good time to plant palms. For more about palms, including the best way to prune them, visit our Palms page.
Cold Feet. One useful trick to keep plant roots cool is to place a large rock or a couple of flat stepping stones right next to the plant on the southwest side thus shading its roots. We used this technique to enable a purple-flowered Clematis Jackmanii to survive in our desert garden. The top of this deciduous vine climbs up an east-facing wall and endures blazing sun until mid-afternoon. The roots, however, are in cooler shade under flat rocks all day long. We also keep the soil at the base of the Clematis well watered.
The Edible Garden. We have become big fans of trees that provide both cooling shade and something to eat. Fig trees are a great way to have your shade and eat fruit, too. They grow fast to 30 feet and cast dark, dense shade in summer, then lose their leaves in winter. Plant one on the southwest side of your home and you will reduce your summer cooling bill significantly! Better yet, most fig trees produce two crops of figs a year. Prune the tree lightly in winter and do not use high nitrogen fertilizer because that will encourage leaf growth rather than fruit growth. The yummy figs grow on the previous year’s new growth. (A quick recipe: stuff quartered ripe figs with chevre goat cheese or cream cheese and wrap in Prosciutto. Some chefs then bake these briefly; some serve this appetizer raw.)
Another good example of combining food and beauty is the Nectarine tree (Prunus persica nucipersica) which can be kept small enough to fit right into a pretty flower border or espaliered onto a trellis. It creates color in the garden month after month — flowers in the Spring, abundant red-orange fruit in late summer, and lovely yellow leaves in autumn. The fruit is only produced on new growth so be sure to prune your nectarine severely in winter before the new buds develop.
We strongly recommend that you “Buy Local” when you invest in new fruit trees. Your local nursery will know which varieties do well in your area. Be sure to ask about “winter chill” requirements. For more about fruit trees and winter chill, visit our Fruit Trees page.
A Thorny Issue. Mesquites (Prosopis) are so common that we have not devoted much attention to them on the Hot Gardens website. These natives of the U.S. Southwest, Mexico, and dry regions of South America, grow very fast, tolerate poor soil and, once they are established in a garden, can often survive with only the water that falls from the sky. On top of that, the wood makes for a great barbecue.
It sounds like a very useful, easy-care tree — right? Well, 30 years ago a group of international foresters thought so and introduced the Mesquite (Prosopis juliflora), a thorny mesquite from South America, into Ethiopia, a country that had lost most of its trees under the pressure of population growth.
Initially, everything went as planned. The Mesquites grew quickly providing wood for cooking, building, and fencing as well as shade. In the past 10 years, however, the success of the Mesquites has become a two-edged sword. The trees love their new environment so well that they are spreading rapidly into arable land, including pasture lands. In a country where raising livestock (sheep, goats, camels, cattle) is the primary source of income, the loss of pasture lands could be a disaster. Worse yet, the thorns are a major cause of injury to herdsmen — and to tires.
The Ethiopian government has addressed this problem by now allowing commercial harvesting of the Mesquite to create charcoal and flooring. The herdsmen, of course, would prefer an eradication program, but the Mesquites are there to stay in Ethiopia. We have also heard reports from Australia that Mesquites introduced there are now beginning to encroach on pasture lands, too.
While we are not native-plant purists, there certainly is a lesson in all this. Consider adding natives to your garden, rather than exotics from other parts of the world.
The thornless Mesquite (Prosopis alba) is shown above. If you are going to buy one be sure to ask for a thornless mesquite because there is also a Prosopis alba with thorns! To complicate matters, mesquites hybridize freely so what a grower may think is thornless will not be when the tree matures. One further note: our favorite mesquite is the Screw Bean Mesquite (Prosopis pubescens) which produces spiral seedpods and is often grown as a shrub.
We want to thank Dr. Joan Padro for bringing this news to our attention.
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