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Index : Shading
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- 5. Shade - A Precious Commodity for Desert Gardens - Landscapes - Top
- Our blazing sun and lack of cloud cover certainly take their toll on plants at this time of year. Gardens are certainly most susceptible, but many landscape plants can also fall prey to sun scorch.
If you purchased landscape plants this spring, you may have notice that on some species, the older leaves have turned partially brown. That's because these plants were likely grown in California, and shipped here for sale. In California, the leaves developed in less intense sunlight. These leaves could not adjust or acclimate to the intense solar radiation here in Tucson. You may have noticed, however, that the new growth on these same plants is uninjured. That's because as new leaves grew, they developed a tolerance to the strong sunlight.
Not all plants have the capacity to adjust. Those that are listed in catalogs and reference books as shade loving are not able to acclimate themselves to full sun. Sun scorch is evident by a yellowing of a portion of the leaves most exposed to direct sunlight. The yellow patch will often turn dark brown or light straw colored, depending on the plant.
Plants which need the most amount of shade are classified as shade-loving or requiring of full shade. Such plants include; Algerian ivy, Asian jasmine and liriope. Shade-loving plants can tolerate the direct summer sunlight of early morning or late afternoon only.
Plants which can tolerate some direct sunlight throughout the day are said to require open, shifting, intermittent, filtered or light shade. They include plants such as; sago palm, heavenly bamboo, star jasmine, privet, and abelia. It's important that some, if not all, of this shade is provided in the mid-day period (10 a.m. to 2 p.m.) when sun intensity is at it's peak. Open or shifting shade refers to intermittent periods of sun and shade. Filtered or light shade refers to that provided under the canopy of wispy trees such as palo verde, desert willow or shoestring acacia. Here dappled sunlight filters through to the plants below.
Plants tolerant of full sun need no shade whatsoever. Most native desert plants are full sun plants. In addition, some plants such as; pomegranate, santolina, yucca, and Texas ranger thrive in full and reflected sun. This means that they can be planted near a light-colored driveway, walkway, patio or wall where light and heat levels are greater than even in open-sun situation. Be careful not to confuse full sun up north with full sun in the desert. Plants that tolerate full sun in northern climates or high elevations cannot do so in the desert.
Of course, many plants tolerant of full sun will grow better with partial shade. These include plants such as; Indian hawthorn, cape honeysuckle, and xylosma. Other plants such as; hopbush, guava, and bougainvillea are tolerant of partial shade but prefer growing in full sun.
Garden plants such as tomato, eggplant, basil, marigold will grow in full sun, but benefit greatly from afternoon shade. Fruits of vegetables are especially sensitive to sun scorch. Unfortunately we cannot apply SPF 30 sun block on our plants. Seasonally, shade can be provided by using shade cloth, or other shading materials such as burlap, lath, and various types of fencing materials.
Permanent shading can be provided by planting trees or by building a ramada or arbor. Fencing may also be placed on the west side of sun sensitive landscape plants and garden beds to screen out the afternoon sun. I particularly like ocotillo fencing because it allows for cooling airflow but can block from 40 to 60 percent of sunlight. Ocotillo is also a "natural" for desert landscapes.
Finally, it's always best to take into account the sun situation in the areas to be planted and then select plants which can flourish in those situations. If you've made a mistake in locating a plant, often the easiest thing to do is to transplant it to another, more suitable location.
This week's garden demonstration will be a "Plant Problems Clinic". Participants are invited to bring their plant questions and samples for answers and analysis. The clinics will be conducted on Wednesday at 9:00 a.m. at the Pima County Extension Center, at 1:00 p.m. at the Wilmot Library, and on Thursday at 2:00 p.m. at Marana Planning Services on the Northeast corner of Orange Grove and Thornydale.
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture and Life Sciences, the University of Arizona.
The University of Arizona college of Agriculture and Life Sciences is an Equal Opportunity employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to sex, race, religion, color, national origin, age, Vietnam Era Veteran's status, or disability. - Updated: June 13, 2001
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