Arizona Landscaping with Fruit Trees: Part 1
Citrus grow extremely well in the lower desert and in fact have been a commercial crop here for over 100 years. The most important aspect of growing healthy citrus is proper watering.
Surprisingly, the weather in the Arizona desert produces some of the best tasting citrus in the world. Heat produces sugar in citrus fruits making them sweeter and cool weather produces acid making citrus more tart. The hot summers and cool winters in the desert therefore produce a much fuller flavored product than can be grown in either consistently warm climates such as Florida, or in consistently mild climates such as the California coast. California’s desert regions produce comparable quality to that of Arizona.
Another advantage that Arizona has over other regions is that citrus here can still be grown on Sour Orange root stock (see propagation section below for an explanation of root stocks), which produces some of the best tasting fruit. California and Florida have both had to ban Sour Orange because of its susceptibility to Tristeza, a citrus disease carried by a brown aphid. Fortunately, this aphid cannot survive the lower desert heat.
Citrus are categorized into the following major varieties. Within these major varieties are many cultivars. There are also some varieties that are hybrids of these varieties, such as Tangelos which are a cross between a mandarin (Tangerine) and a pummelo. The varieties below are arranged from least frost tolerant to most frost tolerant.
- Lemons and Limes
- Grapefruits and Pummelos
- Sweet and Sour Oranges
- Mandarins (includes Tangerines)
Heat Tolerance and Sun Exposure
Citrus tolerate the summer sun well in Phoenix but will always get some sun burned leaves during the hottest weather. Varieties that grow vigorously manage to keep ahead of the sun burn better than varieties that grow more slowly. Kumquats and blood oranges suffer more from the sun than average for this reason.
The trunk and branches of citrus trees when subjected to direct sun can burn badly. In fact, if the trunk of a tree is fully exposed to sun it can kill it. Citrus naturally branch to ground and therefore protect their trunks. However, when a citrus tree is trimmed as a shade tree it exposes the trunk. This is the reason that trimmed up trees have their trunks painted white. Also, young trees should have their trunks wrapped until their branches provide shade. Furthermore, to hasten the establishment of newly planted trees the entire tree should be shaded from afternoon sun the first summer. Newly planted trees do not have a strong root system and can suffer substantially the first summer if subjected to all day sun.
Freezing is generally not a concern in the lower desert unless one lives in an extreme micro-climate, such as a low spot that collects cold air. Most citrus will not be damaged until temperatures are as low as the middle twenties Fahrenheit for several hours. Kumquats are the exception and can handle temperatures as low as 15 degrees F. In slightly cooler climates, such as Tucson, measures should be taken to protect citrus on the coolest nights. See the variety list above to learn how citrus varieties compare to one another for frost tolerance.
Tomorrow we will be looking at Arizona Landscaping with Fruit Trees: Part 2-planting, watering, and fertilizing.