Watering the Summer Landscape
Many of us wonder how the heat or drought will impact our water bill this summer. According to the U.S. Drought Monitor, at the time of this writing, our local conditions are listed as abnormally dry. The southwestern part of the state is in a drought that rivals the severity of the dust bowl era. This started me thinking about my water usage and how can I save on water.
There are no set rules so it is often difficult to know how much or when to water because we cannot see what is happening down in the soil where the roots are developing. But here are some general guidelines that help us make every drop count.
Lawns are one of the greatest outdoor water users during the summer. Many people make simple mistakes that are easily corrected, resulting in savings on the water bill while still maintaining an attractive turf. The most common mistake is not even about water, it is about mowing height. The proper mowing height improves the turf’s ability to withstand heat and drought, thus reducing the need for water. Low mowing height greatly decreases the turf’s ability to fend off summer stress. The ideal mowing height for bluegrass and tall fescue is 3 to 3 1/2 inches. Zoysia should be mowed at 2 inches. This simple practice is key to helping reduce water usage.
Another common mistake is made by those fortunate enough to have an inground sprinkler system. Many people turn on the system then run it on a timer in the spring. This wastes water and money. In spring the temperatures and natural rainfall is usually sufficient to allow us to withhold supplemental watering till late June. Because of our sufficient rainfall this spring, there is no reason a lawn should have any additional watering.
Not watering in spring forces the lawn to develop a more drought resistant root system. Lush moisture at the surface creates a shallow-rooted lawn that will not tolerate summer heat and drought without wilting, and the need for even more water. When the plants have to search deeper for water they develop a stronger root system.
When the need for summer watering does arise then supply about 1 to 1 1/2 inches of water per week in as few applications as possible. Avoid light and frequent irrigation because that creates the shallow root effect.
Vegetable gardens produce best when they have a constant and even supply of water. Stress will impact yield. We recommend watering the garden with 1 inch of water per week. The key is to cover the bare soil with mulch. Mulch reduces soil temperatures, which encourages root development and holds in moisture. Straw, grass clippings or leaves make excellent garden mulch. Apply water at the soil surface instead of overhead to reduce disease development.
Annual flowers should be treated like vegetables for best flowering. Most do best with an even supply of water. Some annuals are touted to be more heat and drought tolerant. But they will still need moisture to grow and flower.
There is growing interest in native perennial plants. They are truly drought tolerant, as they have developed under lean conditions. If you are interested in decreasing the water usage, you will want to start incorporating more into the landscape. Group your plants by their water needs.
Trees and Shrubs
The most important time for proper watering of trees and shrubs is during their establishment phase, which can last as long as three to five years. During their first year after planting they will need to be deeply soaked at least once a week. Watering shallow or more frequently can lead to overwatered plants, as the water does not have time to move through the soil profile.
In periods of prolonged drought these establishing plants will need more TLC. For every year in the ground add one week before supplemental watering. A second year planting will need to be watered about every two weeks. This rule applies up to the point of every four weeks. Evergreens should receive a thorough deep root soaking about every four weeks, if it’s not provided by nature.
The question now is how much is enough water? In the case of a first year tree it could be 10 to 30 gallons of water which slowly soaks the root ball and out beyond the ball, for a distance of several feet. For a large blue spruce it may be almost impossible to supply enough water to help it make it through difficult times. The key to watering is deeply, thoroughly and less frequently. That is the trick to reducing water usage and developing strong plants.
A lawn sprinkler system is not meant to water trees and shrubs. Most irrigation systems water very shallow, only soaking the upper 4 inches of the soil. Tree and shrub roots, while at the surface, are also deeper in the soil, so additional water must be applied to help ensure they survive dry periods. Extension has seen many a dead tree and shrub from inadequate water, with the homeowner protesting, “But I have a lawn sprinkler system.”
Hopefully this has helped you better prepare for what the summer of 2018 will bring. If you have questions contact the Johnson County Extension Garden Hotline at 913-715-7050 or firstname.lastname@example.org. Trained Extension Master Gardeners can assist you.