The Transplanted Gardener
10 Tips for Tending a Successful Desert Garden
Gardeners and homeowners in Tucson face special challenges when it comes to growing plants. And transplanted gardeners—those who knew the lay of the gardening land, so to speak, in a former locale, may find adapting to desert gardening even more difficult. Many of the gardening practices green thumbs learn to trust—the when, the where, the why, and the how—get tossed into the desert wind. Gardening is different in the desert. But the following 10 tips will help make the transition from transplanted gardener to Tucson gardener much easier.
Prime planting time–our spring is actually fall
Spring gardening fever infects us all, but in Tucson, fall is the best time to plant most plants. During fall the warm soil, still holding its heat from the summer sun, promotes rapid root growth. At the same time, air temperatures remain moderate— with no extreme cold or heat to stress new plants. By spring, plant roots respond to warming temperatures, producing healthy top growth. As spring turns into summer, root systems are much more established, giving plants the strength they need to tolerate summer heat. (Plants sensitive to frost, such as citrus, hibiscus, and bougainvillea, are exceptions to the fall-planting rule. You'll generally have better results by waiting until late spring to plant these.)
Adapting to desert soil
Desert soils consist mostly of sand or clay, not loam—the more common soil type in regions with higher rainfall. Desert soils are also alkaline, not acidic. This means we don't add lime to our soil. In addition, our soil contains little organic matter, so we must add compost to beds that contain plants with shallow roots such as flowering annuals or vegetables. Also, mixing generous amounts of ground bark products or compost into the soil helps increase its water and nutrientholding capacity, which helps plants grow better.
Formed from mineral deposits that can develop into a layer of material that's more like concrete than soil, caliche soils require a special approach. Caliche can exist just inches below “normal” soil, preventing plant roots from spreading out of the original planting hole and retarding growth. Even worse, caliche can slow drainage to the point that plant roots suffocate and die. You have two choices here: dig drainage holes through the caliche or grow plants elsewhere. Some gardeners with severe caliche on their property say “I give” and grow plants aboveground in containers.
So many plants, so little time
We can grow an extremely wide range of plants in Tucson. Tropicals, subtropicals, cactus and succulents, native trees and shrubs, flowering perennials, plus plants we've grown in other climates compete for our attention and garden space. It's tempting to give each a try in our gardens, and we often do. Unfortunately, too many kinds of plants can develop into a hodgepodge that is difficult to maintain and not all that attractive. Not only can this make the landscape's appearance less than ideal, many kinds of plants in one garden often means they have a wide range of moisture requirements as well. You can avoid watering problems by zoning or grouping plants by water needs, but cluster plants with varied moisture needs together and it's difficult to water each correctly. Start slowly with your plant selection process. Gradually get a feel for what works together and plan your garden carefully. If you consider the time and monetary expense a landscape represents, gaining the advice of a professional landscape designer may be well worth the investment.
In the desert, lawn is a four-letter word
OK, that's a little harsh. For people with kids or pets, or who just want a spot to walk barefoot, lawns have their place. But our average annual rainfall here is about 11 1/2 inches, not the 32 inches you received in Chicago. As a general rule of thumb, avoid growing lawns for greenery only; low-water ground covers can give you the greenery you seek. Keep lawns a manageable size to keep water consumption to a minimum. Grow adapted warm-season grasses such as hybrid Bermuda for best results.
The ways we water
Watering plants properly is one of the trickiest items to explain, especially to new desert gardeners. Above all, plan on giving newly planted plants frequent irrigations, perhaps up to two or thee times a week during summer. (This is one of the reasons why we plant in fall when the weather is more forgiving.) When plants are established—after they have lived through one or two summers—deep soak the soil every two to three weeks during summer. Apply water in an area around the plant's drip line—near the perimeter of the plant where rainfall would naturally drip from the plant's canopy to the ground.
Installing a drip irrigation system that applies water via emitters with an automatic timer will make your job easier. This way you can control exactly how much water you apply, as well as where and how often.
Pruning–when and how much
Pruning can mystify even experienced gardeners. And in the desert it is not as simple as “wintertime is pruning time.” In addition, many plants, particularly flowering trees and shrubs, do best when pruned right after they cease flowering. Some years our winters are so mild that plants are reluctant to cease their growth cycle. The trick is to avoid pruning too early, for example, in December, but not wait until plants have begun to produce buds, usually by late February or early March. Have your pruning tools sharp and at the ready come mid-January to mid- February. And don't prune unless you have a reason. Pruning just to prune will do more harm than good.
Mulch–it's a good thing
Mulch is just about any material that is applied over the root zone of plants. It can be inorganic, such as rock or gravel, or organic, such as compost or forest mulch (ground bark products). A three-inch layer of mulch over the plants' root zones (beneath the canopy and slightly beyond) reduces moisture loss, retards growth of pesky weeds, and cools the upper layers of soil. Simply put, a mulch serves as an inexpensive method to help plants grow better and use less water.
Respect the power of the sun
Extreme sunshine and heat can stress plants, or even kill them. This is particularly true of plant species that may have thrived in your former home climate but are not adapted to our long, hot summers. The likelihood of such plants failing increases even more if they are placed in a south or west exposure, where sunlight and high temperatures are most intense. Select only the toughest plant for these locations. Also, take advantage of kinder, gentler exposures such as an eastern exposure or a partially shaded location beneath a canopy tree. Likewise, respect the sun's capacity to do you harm. Plan on working outdoors early in the day, before it gets too hot. Wear protective clothing, use sunscreen, and drink plenty of water. Better yet, do the tough work during fall or winter when temperatures are mild.
Not all rainfall is equal
Tucson typically has two rainy seasons: winter and summer. Winter rains are usually slow and steady, which allows moisture to soak into the soil. Summer rains come in the form of intense storms, originating in the Gulf of Mexico and Gulf of California. They are highly localized and capable of producing large quantities of water in a short time. The rain that falls can do more harm than good due to erosion from runoff. Don't let a summer monsoon fool you into cutting back on irrigation. Often when it appears that a rainstorm has moistened the soil, the benefit to plants is negligible. Dig down into the soil to see how far moisture has penetrated.
Become the expert for your garden
With time, growing and caring for plants in our desert becomes easier due to your observations of your garden. It helps to understand the natural progression of our gardening seasons so you can plant, prune, and fertilize in sync with the ebb and flow of plant growth. Consider keeping a written record of activities in your garden—a garden journal. Record planting dates and methods, flowering periods, methods and times of weed control, times when plants were pruned, and how much and when they were watered. Become an amateur naturalist by observing native plants and note when they flower, drop their leaves, or otherwise change gears. Keeping track of such matters will eventually allow you to see and feel when it's time to reach for the pruning shears or when to sow your seeds.
Scott Millard was transplanted to Tucson from Southern California more than 25 years ago. As the publisher of Ironwood Press, Scott specializes in gardening books and guides for the arid West.
Native Seeds/SEARCH 526 N. 4th Ave., 622-5561, www.nativeseeds.org. Keeps native crops and traditional farming methods alive through a regional seed bank and conservation farm.
Pima County Cooperative Extension Garden Center 4210 N. Campbell Ave., 626-5161, www.ag.arizona.edu. Conducts gardening demonstrations on a regular basis in Tucson, Marana, and Green Valley. Master gardeners can answer gardening questions 8:30 a.m.–4:30 p.m.
Tohono Chul Park 7366 N. Paseo del Norte, 742-6455, www.tohonochulpark.org. Offers educational programs, art and cultural exhibits, nature trails, demonstration gardens, a greenhouse, a children's garden, and occasional gardening workshops.
Tucson Botanical Gardens 2150 N. Alvernon Way, 326-9686, www.tucsonbotanical.org. Conducts regular gardening workshops and demonstrates terrific landscaping ideas.