The High Desert climate can produce fruit so good it’s memorable: What you need to know about chill-hours, Southwest Injury, variety, planting, irrigation.
“That just might be the best peach (or pear, or plum) I’ve ever eaten!” Many high-desert residents can bring to mind specific times they’ve heard or made that statement, and they’ll recognize the sigh of deep satisfaction that accompanies it.
They even know it’s possible to get used to high-quality, perfectly juicy fruit with a fully developed flavor and aroma. Still, as they enjoy the springtime splendor of buds bursting into bloom, they’re always aware that a late frost could destroy the crop.
The High Desert, with its combination of winter chill, abundant sunshine, deep soils, and low incidence of fungal disease produces fruits of outstanding quality. But due to its variable weather, a plentiful harvest is never a given.
The best insurance is variety. The more different types of fruit with different bloom times, the better the chance of having some fruit every year (and every kind of fruit in some years.)
While the best cultivars and cultivation practices vary with the locale – High Desert climates in the Southwest differ as much as Tucson differs from Taos or El Paso from Las Vegas–still, understanding the effects of freeze and thaw weather patterns, “chill requirements” and Southwest Injury, as well as some methods for planting, irrigating and pruning are relevant for gardeners and orchardists throughout the area.
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Like home orchardists everywhere, high desert gardeners usually want varieties that will ripen in succession, providing fresh fruit continuously over the longest possible season. However, in the high desert a succession of bloom times is also important.
After a tree has accumulated its required hours of chill, the sap begins to flow. A thaw lasting over a week can cause flower buds to open. It’s at this point that the crop is most vulnerable. Closed buds remain undamaged on the tree throughout winter.
However, even one suddenly cold night can damage open flowers and newly-set fruit. As the young fruit develops a tougher skin, it can weather most cold snaps.
Some species are seldom affected by freeze-thaw cycles. Depend on jujubes, quinces, European plums, late-fall apples, elderberries, black mulberries, and grapes to produce annually.
Like most living things, trees use sensors and internal clocks to synchronize their natural rhythms with local climate and weather. The “chill requirement” is the number of hours below 45 degrees F which must occur before a particular tree will open its buds in spring.
Trees with a chill requirement that’s too low for the locale are likely to bud out prematurely in spring. A chill requirement that’s too high means the tree won’t leaf out until very late (and sometimes not until next year) severely damaging its health.
Lately, some new varieties of low-chill apples and even cherries have been introduced. Anything under 600 hours is suitable for milder areas such as Tucson. However, growers in cold-winter areas should avoid low-chill varieties.
Southwest Injury refers to damage that occurs when winter sun warms tree bark enough to awaken cells from dormancy. They become active and are then damaged when the temperature drops.
This isn’t limited to the Southwest; it’s reported from Virginia to British Columbia. Actually, the name refers to the fact that the susceptible parts of the tree face south or west, The upper surface of horizontal branches are also vulnerable.
Protect the bark by painting it in fall. Use white latex paint, diluted 50/50 with water. The white color reflects sunlight, cooling the tree and also reduces too-early budding in spring. Fruit trees that are vulnerable to Southwest Injury are cherry, apple, peach and nectarine.
Reading about varieties, you may find taste-test winners you’ve never tried, or even heard of. The most delicious fruits you can grow at home are often those that don’t ship well.
So they’re never seen in the supermarket. But they aren’t more difficult. And high desert fruit-growing is all about enjoying something exceptional.
Fall-planting allows roots to develop through the winter, producing stronger spring growth. However, for trees that are subject to Southwest Injury, spring planting makes more sense, so long as they have time to establish deep roots before they must deal with heat stress.
Also, young figs, pomegranates, and white mulberries have thin bark. Plant these in spring and wrap the trunk the first winter.
Select good quality, undamaged stock. Bare-root trees with a large root system, such as are handled by nurseries, will do better than ones with a small bunch of roots in a small plastic bag. Trees that have been “canned up” at the nursery and now have actively-growing new root-tips will do better still.
Soil doesn’t need to be rich but it must have drainage; clay soil is unsuitable if water stands, without soaking in, for two days or more.
Frequent shallow watering creates a weak tree without deep roots that provide reserves against heat-stress and an anchor against high winds.
Soak daily the first week; twice a week through the first summer. After that once a month is sufficient. You’ll know you’ve delivered enough water if just before the next scheduled watering, you dig down and find that the soil a few inches below the surface is still slightly moist.
Prune to a vase form (three or four low branches at a 45 degree angle instead of a leader.) This prevents wind-breakage and helps the tree to shade it’s roots.
All in all, think of fruit-growing in the High Desert as an adventure. Do it because the reward is well worth the uncertainty.