Xerigation

Though installation and maintenance are handled by a contractor, the Landscape Architect must be aware of all factors involved to reduce the long term cost to the client and also conserve water, our most precious resource. Water management should be a major consideration throughout the design, construction and implementation phases of any project where water is a limited resource.

There is a way to survive long, dry spells and still have a green landscape: Xerigation, or efficient watering. At a time when water costs are rising, knowing how and when to water not only promotes healthy plants, but saves water and money as well.

Efficient watering begins with the system you choose. You may want to use several different techniques to water the landscape. Drip irrigation is ideal for watering vegetable gardens, shrubs and trees. Drip irrigation only waters each individual plant. For flower beds and ground covers, you want to use soaker hoses and bubblers. Bubblers slowly flood small areas at a time, and can be ideal for watering planters.

A good irrigation design will allow separate watering for turf, groundcovers, shrubs and trees. This is important because each of these plant groups have different water requirements. The irrigation system should be designed to water each plant-group with the most efficient equipment.

Pop-up spray heads are best for watering turf and low ground covers. Small shrubs and flowers can be watered with shrub sprays or even drip irrigation. Bubblers should be used to water trees, large shrubs and raised planters.

The goal is to use sprinklers that put out large drops of water close to the ground, and do it slowly. Large drops of water are not easily moved by wind, so water falls where it is needed. By sprinkling close to the ground, the amount of water lost to evaporation is reduced.

Another design feature you should look for is a separation of shady areas of the landscape from areas that are exposed to full sun. Such areas of the landscape have different water needs.

First you should understand how the controller operates and what features it offers. If you are not familiar with irrigation, have an irrigator or a manufacturers representative explain the equipment to you.

Knowing how often to water can be a big water-saver. We often think of plants in human terms and want to water them whenever we are hot. However, the best time to water plants is when they need it.

Get to know how plants signal for water. Grass tends to lie flat after being walked on and is dull in color if moisture is low. Many plants lose their gloss and start to droop before wilting. Others will drop leaves, buds or flowers.

The first time you program the controller, start with a once-a-week watering. Watch plants for stress and decrease the number of days between watering if necessary. You can actually harm plants by lightly sprinkling everyday. Frequent light waterings only wet the soil surface. Most plant roots grow much deeper, so don’t fall into the trap of daily light watering.

Each time you water, allow the soil to become wet to a depth of five or six inches. 7 This will promote deeper root growth and allow plants to go longer between waterings.

As a general guideline, plants need approximately one inch of water per week in the active growing season. If you don’t know what the percipitation rate of the irrigation equipment is, find out by following these easy steps:

1. Place four to six empty cans randomly about the project.
2. Irrigate for one half hour.
3. Measure the amount of water in each can; add the amounts and divide by the number of cans for average. This is the amount the sprinkler puts out in one half hour. You can determine how many more minutes are needed to put out one inch.

Run-off may occur when you try to put down one inch of water at one time. Runoff frequently happens on clay soils or slopes, and is the primary cause of water waste. You can avoid run-off by repeat cycling. Divide the total time necessary to put out one inch of water into three or more cycles. Space cycles an hour or more apart to allow adequate time for water to percolate the soil. The repeat cycles should be completed in one watering day.

To keep a state-of-the-art sprinkler system operating efficiently, routine maintenance is a must. The system should be checked once a month (during daylight hours)for leaks, mower or vehicle damage, and vandalism. Keep grass away from all sprinkler heads with regular trimming. Also make sure that the sprinklers are still spraying onto the plants and not walkways, drives or buildings.

Water pressure changes can affect efficiency after an irrigation system is installed. Higher pressure will cause sprinklers to “mist” or “smoke”...and water is blown away. Lower pressure may result in sprinklers not being able to pop-up completely or operate properly. Call an irrigation professional to help with these problems.