Curt Swift
CURT'S CORNER
CSU Extension Horticultural Specialist
Grand Junction Free Press Gardening Columnist

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July 5, 2012
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What to do when your lawn needs a big drink

GRAND JUNCTION, Colo. - The other day I arrived home at noon and my lawn was blue. It had turned blue due to being under water stress; in other words it needed a drink.

I turned on my sprinklers and lightly watered (syringed) the portion of lawn that was dry. Yes, I did this in the heat of the day. No, this will not damage my turf, in fact, this brief watering is known to improve the health of your turf when it is under stress by cooling the turf canopy. It helps prevent wilting. If I had pop-up spray nozzles, I would have run the zone covering the dry area for five minutes. Since I use MP Rotator nozzles that put out much less water than spray nozzles, I ran the zone for 15 minutes.

If I had impact heads I would have run the zone for 15 minutes. I followed up the syringe with a full application of water that night.

When turf gets hot and the roots do not absorb sufficient water to replace the water lost through transpiration, the grass wilts.

You know this has happened when the grass blades do not return to their original upright position when you walk across the lawn.

This "foot printing" will be followed by a gray to blue-green to slate color change of the leaves. When wilting occurs, respiration increases, photosynthesis slows, and stomates close.

The reduction in carbohydrates available for the metabolic processes of roots, as well as water being pulled from the cells, results in root death.

When roots dry out and die, the grass will need to be watered more frequently than otherwise would be required. Syringing helps prevent this.

Roots take in water only from the soil in which they are growing. If your grass has a two-inch root depth it only has access to water in those two inches.

The amount of water available in those two inches depends on the type of soil. For example if you have a silt clay loam soil like I do, this soil can only hold 0.16 inches of plant available water (PAW) per inch of soil.

Thus two inches of this soil has only 0.32 inches of plant available water. Since plants need to be watered when 50 percent of PAW has been used, you will need to water when 0.16 inches of water has been used by the plant. At present, the plant water use (evapotranspiration) in western Colorado is about 0.30 inches per day for turf. Thus if you have a root system that is only two inches deep, and your soil is a silt clay loam, you will need to water twice a day to ensure the grass has sufficient water to prevent it from going dormant.

If your lawn has roots six inches deep and the ET is .30 inches per day, then you can water every three days without causing problems with your lawn.

You can tell how deep the roots are by cutting out a section of your lawn with a shovel, or trowel.

Dig a hole about eight inches deep and take a slice off the edge of the hole. Starting at the bottom of the slice of soil, break the soil apart until you find the first root.

This gives you the depth of the soil from which the grass can absorb water.

To make a drought-tolerant grass, you need to promote deep roots. You need to do whatever it takes to keep those deep roots alive.

Syringing is a technique that helps keep the roots alive.

Even though lightly watering in the heat of the day results in a large percentage of the water being lost through evaporation, this practice helps prevent root death and therefore results in less water use than is otherwise needed to keep the lawn healthy.

If you are on water restrictions you may not be able to water often enough to keep the lawn green. If that describes your situation, stop watering.

It does more harm than good to have your lawn start to go dormant and then attempt to recover when you apply water.

If you have an established lawn it should be able to survive for two to three months without water. Established trees and shrubs in the lawn will still need to be watered. Drag a hose and water under the canopy of the trees and shrubs.

A watering once or twice a month should be adequate for the survival of these trees and shrubs.

If you have questions on how to care for your lawn during these hot days, look me up this Saturday, July 7, at the Colorado Lavender Festival in Palisade. I'll see you then.

Dr. Curtis E. Swift is the area horticulture agent with the CSU Extension. Reach him at Curt.Swift@mesacounty.us, visit WesternSlopeGardening.org, or check out his blog at http://SwiftsGardeningBlog.blogspot.com.


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The Post Independent Updated Jul 5, 2012 04:47PM Published Jul 5, 2012 04:44PM Copyright 2012 The Post Independent. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.