Although the desert regions of the American Southwest do not have the extreme winter-weather conditions of many parts of the US, nevertheless they do have a winter.
Simply, gardeners must take a number of factors into account.
Although daytime temperatures are usually quite pleasant, there is a great deal more variance between the highs and lows than in most places. If the high in the afternoon is in the 50s and 60s, the mercury often plunges to near or below freezing a night.
At times it may drop as low as 20 degrees F., or even less, in low-lying areas that receive cold-air drainage from higher elevations. This is especially true along river courses.
Heavy-frost dates run from mid-November to mid-March.
With these factors in mind, the desert gardener begins to prepare his winter garden around mid-October. By this time the melons, squash, cucumbers, and other summer crops are reaching the end of their production.
These are pulled up and the beds enriched with compost and steer or chicken manure.
A few crops, such as tomatoes, eggplant, and peppers, will still be bearing, and these are often left to produce until the first hard freeze destroys them, usually around mid-November.
Some gardeners keep tomatoes in containers, moving them under a sheltered porch or patio roof on cold nights, thereby having fresh tomatoes almost all year long.
When the daytime temperature drops below 90 degrees F., the winter crops are planted. These consist of cauliflower, cabbage, and broccoli, which are usually bought from nurseries, individually or in flats; and of lettuce, carrots, Swiss chard, beets, and radishes, which are grown from seed.
Kohlrabi also is a seed-grown crop which does quite well in the winter desert garden.
All of these plants are quite tolerant of freezing temperatures, althouth it is advisable to cover the beds with burlap or other protective material on extremely cold nights. There is often only a very few days during an entire winter when a hard freeze will occur, but it only takes one to wipe out an unprotected garden.
Since freezing has a dessicating effect on plants, it is wise to keep the garden well-watered during cold spells. Although there is a winter rainy season in the desert, it cannot be relied upon to provide much moisture for a garden because only 4 to 6 inches may fall during the entire period.
Cabbage worms can be a big problems in the winter garden. These little green caterpillars, which are actually the larvae of several different species of moths and butterflies, can be destructive to almost all of the vegetable crops.
One of the best remedies is a bacterial spray which works specifically on these creatures but does not harm birds, pets, and humans.
Often the simplest and most economical solution is to look over the plants carefully each morning and pick off any caterpillars or other pests. A helpful parasite, unknown to most gardeners, is a fuzzy black fly which lays its eggs upon the caterpillar. The fly larvae then hatches and enters the body of the caterpillar where they destroy it.
At times, cutworms may also destroy young plants, but this condition can be remedied by placing a small paper or plastic collar around the base of each new plant.
Aphids can be a serious nuisance as well, particularly on cabbage and broccoli, but periodic spraying with a garden hose will knock many of them off, while white flour sprinkled upon them reduced their numbers, too.
Some gardeners feel that planting onions or marigolds among the other plants will greatly aid in keeping aphids and other insect pests out of the garden.
It should also be remembered that the fresh greenery of a desert garden will attract larger pests, such as birds, rodents, and rabbits, which may be having a hard time finding food at that time of year, especially during a dry winter.
Even deer and javelina will prey upon garden vegetables in the outlying areas.
Adequate fencing or screens and nets may be necessary to keep them out. Dogs and cats which have access to the garden are a great boon to the gardener in keeping the smaller creatures away.
It is a good idea to plant some of the winter crops at intervals, thereby assuring oneself of a longer period of production. This is particularly true for radishes, which grow much more rapidly than most plants. Planting a row every other week will keep a steady supply of fresh young radishes on the table for a long time.
For those who wish to raise flowers, the winter desert garden is ideal. Many types of flowers, which cannot take the extremely hot and dry spring, summer, and fall months of the Southwest, will thrive in mild winters that follow.
African daisies are one of the favorites. The streets and gardens of southern Arizona are lined with their brilliant colors from midwinter to late spring. Petunias also do well, as do snapdragons, stock, and zinnias.
The type of flowers one is able to grow here varies greatly, depending on the location, because only slight differences in elevation can mean the difference between the success and failure of the most delicate varieties.
Even roses do well during all but the coldest days of a desert winter.