June 2012
The Magic of Gardening

Keeping the Landscape Healthy Without Breaking the Water Budget


     Mulch bed around oaks and shrubbery.

Even though watering restrictions are not yet commonplace throughout Alabama, homeowners should still take measures to conserve water. I have seen more plants killed by overwatering than under-watering. Overwatering does more than deplete the water supply and our bank account; it also makes plants more prone to pests, more drought sensitive and adds to our collective stormwater runoff problem. Stormwater runoff pollutes our streams and lakes by moving fertilizers, soil and chemicals into the waterways.

By choosing and operating a watering system correctly, you can reduce water bills, insect and disease problems, make grass or shrubs more drought tolerant and reduce maintenance requirements. To maintain a healthy lawn in sandy soils may require as much as two inches of water per week during peak growing season, but in most soils one inch per week is sufficient. The more you water your lawn, the faster it grows and the more it needs to be mowed. Warm-season grasses are generally very drought tolerant and will simply go dormant during a drought if the roots are trained to grow deep. You train deep roots by watering infrequently, but deeply, after initial establishment. Many irrigation systems are set to run three times or more per week and those lawns lose a lot of water to evaporation and encourage shallow root development. Many homeowners feel compelled to run the irrigation even if the lawn does not need the water because they feel it justifies the initial expense of the system. However, we should think of the irrigation system as insurance or maybe like a vitamin. Our body needs vitamins, but we can get too much of a good thing and cause other problems. We also like insurance, but mostly we like having the peace of mind it gives us and we are not anxious to use it – especially life insurance.

What’s true for turf is even truer for established trees and shrubs which may require less than half as much water as an established turf. In most years, we get enough rainfall for well-established trees and shrubs, and they do not need regular irrigation. If you have thirsty plants like hydrangeas, azaleas or dogwoods, low volume drip or micro-sprinklers are a much more efficient way to water than solid set sprinkler systems.

To save water, don’t rely too heavily on these thirsty landscape plants, but choose mostly water-efficient and drought-tolerant plants including tough heirloom shrubs, trees and the sturdier native plants. If you group plants according to their water needs (called a hydrozone), you can simplify watering methods and systems. For example, turf areas and shrub areas should always be separated into different hydrozones. They do not need the same amount or frequency of water. Enclose trees and shrubs into large mulched beds rather than small rings or, worse, no rings surrounded by turf.

For turf areas, install a rain shutoff device or soil moisture sensor (if you have an automatic sprinkler system) that will override the system when it rains or when the soil reaches a preset moisture level. Your county’s Extension office, the Natural Resources Conservation Service or a certified irrigation professional can provide technical assistance. Except for the first couple of years of establishment, you do not need permanent irrigation for most shrub and tree beds. Flowers and thirsty shrubs are the exception and should be watered on an as-needed basis rather than on a regular schedule like turf.

Water turf in the early morning from 4 to 7 a.m. This is the most efficient time because temperature and wind speeds are usually at their lowest; this in turn reduces evaporation and, more importantly, off-target drift. Also, grasses are less susceptible to fungal problems if water is applied at the time dew normally forms. Avoid watering between 10 a.m. and 4 p.m. Temperature and wind speeds are at their highest during this time so water waste is more likely. Do not continue to water during the winter months. In most years, you can turn the system off and drain it in November and leave it off till late spring. An exception would be the year of establishment.

Lastly, calibrate your sprinkler system regularly. Make sure it is putting out water evenly over the entire area. Also, look for broken or leaky sprinkler heads. Sometimes what you think is a leaky sprinkler head is really low head drainage. If you are on a slope, water will run to the lowest head and drain from the pipe. You can stop this problem by installing heads with built in check valves or by adding check valves under existing sprinkler heads.

There are many ways to save water and reduce stormwater runoff. Visit the Alabama Cooperative Extension System website and look at the "Alabama Smart Yards Handbook" for more good tips (http://www.aces.edu/pubs/docs/A/ANR-1359/ANR-1359.pdf).

Tony A. Glover is a County Extension Coordinator in Cullman County.