   Drought Tolerant Plants - June 17, 2009 Jeff Schalau, Associate Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County Drought is defined as a deficiency of precipitation over an extended period of time, usually a season or more. Other climatic factors such as high temperature, high wind, and low relative humidity can increase drought severity. These conditions are very familiar to Arizona residents and rather than responding to drought, we should plan for it. One way to anticipate drought is to reduce the amount of water applied to landscaping. The term “xeriscape” was coined by Denver Water employees and refers to landscaping in ways that reduce (or eliminate) the need for supplemental irrigation. This water conserving strategy relies on plants that can tolerate extended drought periods once established. Drought tolerant plants should be regularly irrigated for the first couple of years to help them become established. New landscapes are often installed with drip irrigation systems. Some supplemental irrigation is necessary for successful plant establishment. Irrigation water must be directed to not only the original rootball, but also the surrounding native soil to encourage a well-distributed root system. This will also help the plant to withstand high winds and utilize natural precipitation when it occurs. This is often where drip irrigation systems fall short because these system are usually designed to only deliver water to a small area of soil near the original root ball of the plant. The key to successful xeriscaping does not end with simply planting and establishing drought tolerant plants. Following establishment, homeowners must also allow these plants to express their drought tolerance by actually reducing the amount of irrigation applied. Native grown plants often have fewer leaves, smaller flowers, and/or a slower rate of growth than that of a regularly irrigated plant of the same species. The idea is to get your landscape plants established then cut back the irrigation so that they can withstand drought conditions. You should also resist the urge to fertilize drought tolerant ornamental plants. Fertilizing ornamentals will produce weaker wood, cause the plant to grow excessively fast which often leads to the need for pruning. A well fertilized plant can also produce succulent growth which is more attractive to animals and insects. Pruning causes wounds which require energy to heal and exposes plant tissue to infection by disease causing organisms. Drought tolerant plants should never be sheared to shape them – the lack of applied irrigation will cause the plant to develop a natural shape and limit growth. Texas sage is a prime example of a plant that becomes less healthy when sheared. Drought tolerant native plants have the added benefit of providing familiar habitat for native birds, reptiles, mammals and arthropods. Conversely, non-native drought tolerant plants are less familiar to the native fauna, and when used in the landscape, may offer some advantages in the way of increased pest resistance (native pests may not be able to utilize them for food). Whether native or non-native, drought tolerant plants will conserve water. Recently, a local horticulturist, Dusty Eiker, and I created a new plant list titled Drought Tolerant Native Plants for the Verde Valley. This list also contains a section with several non-natives which are also well-suited for the area. Arizona Department of Water Resources (ADWR) employee Crystal Frost also assisted in compiling this list and was instrumental in coordinating the effort. The plant list is two pages and contains 31 tree species, 50 shrub species, 9 cacti/succulent species, 15 grass species, 11 perennials, 8 ground cover/vines, and 7 invasive plants that are drought tolerant, but should not be planted. It has both common and scientific names for each species. This list is not designed to be comprehensive and contains some plants that may not be readily available in the nursery trade (but are native to the area and should be conserved where possible). However, it lists many plants, native and non-native that will use less water following establishment. This drought tolerant plant list is downloadable at the following URL: cals.arizona.edu/yavapai/publications/yavcobulletins/droughttolerantplantsforthe verdevalley.pdf. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at cottonwoodmg@yahoo.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |