Landscapes change naturally with the seasons. But sometimes we change our mind about what our overall landscape should look like. It may be you bought your home with the existing landscape as per the developer’s design, but your needs have changed. Maybe you want more color, or you want to reduce your water bill by reducing the lawn area.
Many new developments have basic designs: lawns with trees and shrubs planted in and around them. As those trees have matured, your landscape may appear primarily green, lacking color diversity most of the year. Whether your goal is to add color, conserve water or both, it’s likely you’ve decided to reduce the size of your lawn area. In this case, the most important thing to remember is, do it carefully. Nothing will kill a shade tree faster than ignoring your trees in the process of lawn conversion.
In the planning stages of lawn conversion, there are many things to consider, from design to plant selection to the amount of lawn you will remove. In a typical older landscape, the trees are irrigated by the original drip system designed for young trees, with only one or two emitters. The majority of the trees’ actual water needs are provided by the adjacent lawn sprinkler system. Because of this, the tree roots are likely very shallow, within the top 12 inches of soil. These roots have also spread beneath the lawn, taking advantage of the extra water that was provided by lawn irrigation. You must take this into consideration in your new design, so that you continue to provide moisture to those existing tree roots. If you don’t, your trees will experience dieback of major branches and slowly decline over the next few years.
Depending on how much lawn you are removing, you may be able to keep your existing irrigation system. In retrofits where only 10 to 20 percent of the lawn is removed, the existing irrigation system can remain in place, and the lawn-free areas can be mulched and other plants incorporated. If you’re planning to remove more than 25 percent of your lawn, in most cases, you must adjust the irrigation system to reduce the amount of water you use. An expanded drip system would be ideal, scheduled to provide deeper, less frequent irrigation.
Perhaps you plan to remove most of your lawn, and will keep only a small section. Consider using organic mulch such as shredded bark where the lawn used to be, or even a living mulch, a ground cover, that will reduce the amount of time and water required. This creates an environment that is more favorable for your trees and their existing root system. If your trees have been in the landscape for more than five years, expand your drip irrigation system to cover at least the area within the tree’s dripline, and even beyond. Provide enough water to reach at least 18 inches into the ground, testing the depth of water penetration with a soil probe or long screwdriver.
For extensive retrofits, seek assistance from a landscape professional or company that works primarily with retrofits. Certified qualified water efficient landscapers (QWEL), or a company who employs them, have the unique training to provide for your new water efficient landscape needs. Visit www.QWEL.net to locate a professional near you.
Wendy Hanson Mazet is a plant diagnostician with University of Nevada Cooperative Extension. Have questions about your plants? Contact a Master Gardener at 775-336-0265 or firstname.lastname@example.org.