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Water used wisely promotes happy plants

Posted Tuesday, June 14, 2005 - 9:50 am

By Durant Ashmore

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It's time to consider transplanting plants, trees (11/22/05)
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Autumn leaves are nature's gift for mulching (11/08/05)
Plant colorful winter annuals without delay (11/01/05)
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This year we are experiencing a regular series of rainstorms that are watering our plants to a fairly sufficient degree. There have been times this year when our natural rainfall has needed an additional boost from us to provide landscape plants with enough water. Also, the hottest part of the year is just around the corner. During periods of dry weather or excessive heat it is advantageous to water plants by using an irrigation system.

Irrigation systems today apply water through three different types of irrigation heads. These types are gear-driven rotary heads, spray heads and drip emitters. Gear-driven rotary heads spray in a gently rotating pattern usually to a distance of 35 feet. These heads have replaced the impact heads which were used in the landscape for the past 50 years. Gear-driven rotary heads have fewer moving parts and wear out less often. These heads are typically used to water lawns.

Spray heads spray water in a fixed pattern determined at the time of installation. The usual radius of these heads is 15 feet, and they typically are used to water foundation plantings and small grass areas. Do not under any circumstances mix spray heads and rotating heads on the same zone. You will wind up with very unequal water distribution.

Drip irrigation is used to water trees, shrubs and flowers. By using a series of tubing it places water directly on the root ball of the plant. This is the most effective means of conserving water in the landscape (drip irrigation was developed by the Israelis for agricultural production in the desert). Since drip tubing is placed on top of the ground under mulch it also is the cheapest form of irrigation because very little digging is involved. One drawback to drip irrigation is that it requires frequent monitoring. Dogs and chipmunks will chew on the tubing. Insects can nest in the emitters and clog them. Drip irrigation is not as permanent as a ground system installed with hard PVC pipe. Usually, the homeowner doesn't know the drip system isn't working until the plants start to die.

The design of an irrigation system is crucial. Irrigation supply houses will design systems for free if you buy the parts from them. There are many professional installers available, but there are also many who do not have the skills and knowledge to properly design a system. Do not let the quoted price of a system be the determining factor in deciding on irrigation installation. There are many cheap systems out there, and always someone available to do one cheaper.

After a cheap system is installed it can become expensive to straighten out. The irrigation contractors who are making money out there are the ones straightening out poorly designed systems. It will cost $25 to $40 an hour to correct a system that has been improperly designed.

Sprinkler heads should be placed on the outside edges of the area to be watered and directed toward the center. If the heads are placed in the middle and directed toward the outside, you have a poorly designed system. The middle will get soaked while the outside areas remain dry. Spray heads should be placed next to the house foundation and directed away from the house, never toward it. Since lawns have different watering requirements for shrubs and flower beds it is usually best to have lawn areas on separate zones. There are many other design factors to take into consideration. Before you commit to irrigation installation be sure you are dealing with someone who understands the importance of proper irrigation design.

Assuming you have a properly designed system, the next question is how often to run it. Our frost free days in this area are considered to be between April 15 and Oct. 30. This is the only timeframe considered necessary to provide additional watering for lawns or landscape plants. Run the system every other day with the goal of applying 1 inch of water per week. The system should run only in the early morning when natural dew is present. Watering at other times of the day will lead to fungus. Usually the spray zones run 8-12 minutes each and the rotary heads run 20-30 minutes each. This should give the proper amount of water without waste.

If you have an irrigation system, it makes sense to have a separate irrigation water meter. By doing this you avoid paying sewer tax on the water that you are using for irrigation (this may be more than half your bill). Also, there is a new regulation that requires a yearly inspection of the required anti-backflow device on the irrigation system. For $35 to $65 per year a technician is required to give the anti-backflow device a yearly check to make sure that it is functioning properly.

Most landscapes in our area require water in order to thrive. Please use our water sensibly with a properly designed system and an understanding of how to apply water so that it is not wasted.

Editor's note: Columnist Durant Ashmore, MLA, of Fountain Inn, is certified by the South Carolina Nursery Association. He can be reached at 243-3446 or at

Wednesday, June 23  

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