Gardening : It’s Easy to Cut Water Use on Lawns by 10%

Most gardeners when asked to save water look no further than the lawn. It’s the obvious place to cut back, especially when 10% is all most of us need to save to get us through this year’s drought.

It doesn’t take much effort to save 10%. “Most grasses have a 20% built-in buffer,” says Victor Gibeault, extension environmental horticulturist at UC Riverside. Water and fertilize 20% less than optimum and you will not notice the difference.

This means that now is not the time to take drastic action. Planting something other than grass, or converting from one lawn grass to another at this point would require more water than simply maintaining what you have.

The one exception might be trouble-prone bluegrass (if anyone still has a bluegrass lawn), but only if it is to be replaced by a warm-season grass such as Bermuda grass.

Surprisingly, Gibeault says that the latest findings show that the much-touted tall fescues can use as much or more water than bluegrass. However, because they are tougher and are much deeper rooted, they can survive with less water if necessary, though their appearance is going to suffer, and they don’t have to be watered as often.

Good old Bermuda grass is still the best for Southern California, despite it’s long winter dormancy. Warm-season lawns, which spread by stolons and grow during the warm months of the year, are proven to use 15% to 50% less water than cool-season lawns. There are newer warm-season grasses, such as seashore paspalum, ‘El Toro’ zoysia or the Buffalo grasses (which won’t appear on the market for a year or more), but “Bermuda grass is still tops” for toughness and water-saving, says Gibeault.

Except in the mature, shady garden. Here St. Augustine grass is probably best though tall fescues and ‘El Toro’ have shown shade tolerance. Bermuda does not like shade at all.

Bermuda grass especially, but other grasses too, tend to build up a thick layer of thatch--the dead stolons and blades the make a cushioned mat at the base of the grass. Thatch can make watering a lawn difficult, if it gets thicker than one-half to three-fourth of an inch because it repels water.

It can be removed with a machine called a vertical mower, that slices it out of the lawn and this might be the year, and the time of year, to do this yourself (rent the machine) or have it done (look under “lawn maintenance” in the phone book). At this time of the year, lawns recover quickly given a little fertilizer.

At the same time, if you suspect that the soil under your lawn is dense and compacted, you might have it aerified, using a machine seen on golf courses that pulls out plugs of soil so water can penetrate.

Other measures you can take to save water are much simpler.

Start by turning off automatic systems and watering only when the lawn needs it. No lawn should be watered every day and most need water only every three to five days, depending on soil type and where you live.

In general, 1 inch of water will soak only 6 inches deep in a clay soil, 1 foot deep in a sandy soil. You want to encourage roots to grow at least a foot deep, so you need to water long enough to fill a cup or coffee can with 1 to 2 inches of water. Set a container out on the lawn and keep track of how much water you are applying.

Once you know that you have applied enough water, wait as long as a week before watering again. If you notice that grass growing in sun does not spring up after being walked on, you have waited too long and it is time to water. An even better method is to buy a soil probe that takes a core of soil out of the ground so you can examine it and see how dry the soil is a foot down.

What if the water doesn’t soak in? This could be thatch or compacted soil, but it also might be soil that is hydrophobic, which mean it’s water-repellent.

Nurseries sell special wetting agents or “saturants” that help the water soak in. Or, try watering in cycles. Turn the water on, then off while it soaks in, on again, then off, until you have filled your coffee can to the proper depth.

Some parts of the lawn may get much more sun and heat than others. Instead of watering the whole lawn when these suffer, use a portable sprinkler just to water these areas more frequently. Gibeault doesn’t recommend watering the lawn just to cool it off on hot days, and he doesn’t see any benefits from mowing grass taller than normal (to shade the roots). Common Bermuda should be mowed so it is 1 to 1 1/4 inches tall, hybrid Bermudas one-half to three-quarters inch tall, 1 1/2 inches for tall fescues.

Cut back on fertilizing, but don’t stop. Lawns need nitrogen to maintain growth and stay healthy, but too much nitrogen causes excess growth and uses more water. Cool-season grasses, including the tall fescues, need fertilizing now and in the fall but not in summer.

Beyond these cultural practices, look for the obvious sources of wasted water sprinklers that are covered with grass and don’t spray properly (trim grass away by hand or replace with high pop-up sprinklers), sprinklers that water the street or sidewalk (adjust the nozzles by turning the screw on top), leaky valves or broken sprinkler heads.

Ten percent is not a lot of water to save but if you think things are only going to get tougher in the future, start planning now how to use less-thirsty plants in the landscape. If you want to cut down on the size of the lawn, or replace it entirely, fall is the time.

WATER-SAVING LAWN CHECKLIST

* Turn off automatic sprinkler systems.

* Water deep, but less often.

* Water in cycles so water soaks in.

* Remove thatch and aerate soil.

* Mow at proper height.

* Fertilize less.

* Clear and adjust sprinkler nozzles.