Weekend Gardener: Consider landscape when choosing irrigation

Friday, September 8th 2000, 12:00 am
By: News On 6

After a summer of dragging garden hoses around the landscape, many homeowners are thinking of installing an automatic irrigation system.


With water in short supply, select an irrigation system that will apply water as efficiently as possible. An irrigation system can be anywhere from 57 to 91 percent efficient.

What influences the efficiency of an irrigation system? Type of system, design, emitters, soil, plants, mulch, time of day, length of time and wind speed all affect its efficiency.

Select the type of irrigation system to meet the requirements of the landscape. Even soaker hoses and drip irrigation can be made automatic using a timing device that attaches to garden faucets. The device is a simple timer that works without electricity.

An in-the-ground automatic sprinkler system on an electric timer programmed to run every five days will save time, but is only as efficient as the design and emitters.

A good sprinkler system design zones the watering stations according to the types of plants, such as trees, shrubs, flower beds, ground cover and turf area. The turf area uses the most water, so the first step to achieving water efficiency is to reduce the turf area as much as possible by planting more shrubs, ground covers and flowers.

Not every station will require the same operating time. Select a timing device with flexibility to meet the requirements of the different zones or stations in the landscape, and check each zone for water efficiency.

Install emitters to apply water as low to the ground as possible. The less time water is in the air, the less water is lost to evaporation. This is one reason drip and soaker hoses are so good - they apply water close to the ground.

No single emitter type fits all locations. Use different emitters to apply the water in a pattern so no water falls on the driveway, sidewalk or street. An emitter should apply water at the rate the ground can absorb the water without runoff.

Sand, clay and amended soils absorb water at different rates and hold water for different lengths of time. Zone the irrigation system according to the different requirements.

When clay soil is dry, it becomes hard and water has a difficult time penetrating the surface. When clay soil remains wet, plants suffer from lack of oxygen.

Water runs through sandy soil. Add organic matter to clay and sandy soil in all shrub, ground cover and flower areas. Continually add more organic matter as mulch.

In the lawn areas, practice the "Don't Bag It" mowing program by using a mulch mower. This will continually add organic matter to the soil which increases the water-absorbing and water-holding capacity of the soil.

Landscape with plants that require little water. It is possible to have a beautiful, flower-filled landscape even during a hot dry summer like this. Go to Veterans Park to see the Xeriscape and wildscape demonstration areas. There are many flowering plants even in this heat.

Mulch all areas of the landscape at least two or three times a year. The best mulch is your own yard waste. Place all yard waste on the driveway. Mow over the yard waste to reduce the size, then place the waste under shrubs and flowers and around trees.

Compost the yard waste to add to the lawn area. A half inch application of compost to the lawn area in the spring will make a huge difference in the amount of water needed.

How often and how long should you water? With water conservation requirements in place, water every five days for lawn areas. Shrubs, flowers, containers and even trees can be watered more often.

How long to run the water is influenced by time of year, soil, temperature, wind and humidity. Plants need less water in the winter.

Water between 8 p.m. and 10 a.m. during hot summers. Less water is lost to evaporation at night. Do not water in high wind, which displaces the water pattern and leaves some areas underwatered.

Water infrequently and deeply to create deep roots. Deep-rooted plants need to be watered less frequently.

But roots will only grow deep if there is water and deep water has been depleted by the extended drought. To water deeply, water slowly to a depth of six inches. It takes one to one-and-one-half inches of water to penetrate the soil six inches.

Place tuna or cat food cans around the landscape to measure the amount of water applied. Dig a few test holes to see how deep the water penetrates the soil. Adjust the watering time according to what you find.

Do not allow runoff, which flows into storm drains. Runoff occurs when water is applied faster than the ground can absorb it. Run each station two or three times for short periods instead of all at once to avoid runoff.

This is not the first hot, dry summer in this area and it won't be the last. A beautiful green and flowering landscape is possible with proper planning, planting, irrigation, mulch and understanding all the factors influencing the landscape. Water smart.