Irrigation

Watering Tips for Lawns

Water usage in the Inland Northwest during the winter months averages 200 gallons per household per day. During the summer water usage jumps to 885 gallons per household per day. Lawns can be the household's largest water consumer. Making sure your sprinkler system is operating properly and watering at the right time can help reduce water use and still give you a nice green lawn.

How Much Water Does My Lawn Need?

Watering rates vary based on turf type and soil type, but in general 1 inch of water per week will keep your lawn green through the growing season. That water comes from rain and your irrigation system. Adjust your irrigation schedule based on rainfall.

How Often Should I Water My Lawn?

Deep watering encourages deep-rooted grass. Shallow watering encourages shallow rooted plants. Deeper-rooted grass is more drought tolerant and can go longer periods of time without water. Giving you lawn ½ inch of water twice a week will promote deep roots. Shallow soils or clay soils may not absorb water quick enough to apply ½ inch of water per application. If you notice water running off you can reduce the amount of water per application (1/3 inch of water 3 times a week) or replace your sprinklers with another type that applies water more slowly.

How Long Should My Sprinklers Run?

Every sprinkler system is different and you need to do a simple catch-can test with yours to determine how much water your system is delivering. Place several small plastic containers around your lawn, turn your irrigation system on and time how long it takes to apply the desired amount of water. If it takes 20 minutes to reach ½ inch of water in the container, set your system to run 20 minutes twice a week to apply 1 inch total. Measure the water in each catch-can to check for even distribution. If some cans have more water than others you may need to adjust your sprinkler heads.

What Time Should I Water My Lawn?

Run your irrigation system during the cool morning hours to prevent water loss through evaporation. The best time is between 4:00 AM and 11:00 AM. Avoid watering during the hottest part of the day. Also, avoid watering late in the day. Grass that stays wet overnight is more susceptible to disease.

What Type of Grass Should I Plant?

Most lawns in the Spokane area are planted with Kentucky bluegrass for sunny locations, and a mix of fine fescue and Kentucky bluegrass for shade. Some people are using turf alternatives in their lawns, such as clover and yarrow mixed with grasses, which require much less water than traditional turfgrasses. Tall fescue is not as popular, but can be used in lawns.

Is There a Low-Maintenance, Drought Tolerant Turfgrass?

Several commercial retailers sell various drought tolerant turf, or dryland seed mixes. For the Inland Northwest, a mix of fine fescues (hard fescue, sheeps fescue, Dawson's slender red fescue, chewings fescue, and creeping red fescue) may be the answer you are looking for. These fescues are slow growing and drought tolerant. This means you mow and water less.

Establishing a Lawn

Whether you are seeding or laying sod, spring and fall are the best times to establish a new lawn. Taking advantage of mild temperatures and seasonal rainfall will help your new lawn establish. The key to success is to keep the soil constantly moist, not saturated. This means you water lightly several times each day until the seed has established or the sod has rooted into the soil. After 4 weeks your lawn should be well established. Change your water schedule from frequent, light applications to infrequent, deep watering.

Prepare Your Soil Before You Plant

Before you plant seed or sod, you have the chance to improve soil quality in your lawn areas. Amending soil with compost increases the water holding capacity of the soil. If the soil holds more water, more water is available to the grass over a longer period of time. Spread 1 inch of compost over the soil and till it into the top six inches. Compost can also be used in flower beds and vegetable gardens.

Watering Trees and Shrubs

If you are using an automatic irrigation system, trees and shrubs should be irrigated separately from lawn areas. This is due to different water needs and different sprinklers used for trees and shrubs. Drip irrigation or spray heads can direct water to the roots of trees and shrubs. Rotary spray heads used for lawn areas apply water very quickly. When watering trees and shrubs, water slow and deep. Tree roots can extend 2-3 times the height of the tree. Most of the tree's water absorbing roots are within the top 12 inches of soil. Applying water to the entire root zone of trees may be difficult. Focus on watering the area beneath the drip line of the tree. Watering is most important during dry summer months and late fall before the ground freezes over the winter.

How Much Water Do I Apply to Trees?

A general rule is 10 gallons of water are needed for each diameter inch of the tree. A five inch diameter tree would need 50 gallons of water under the tree's canopy per watering. Many of our native trees such as Ponderosa Pine are well adapted to our environment and are able to survive without supplemental water. Other ornamental trees such as Maple and Birch require supplemental irrigation to survive, even if the tree is well established. Provide water during dry summer months and in late fall when temperatures are above freezing to prevent winter kill.

Mulch to Conserve Moisture

Avoid growing turf right up to the base of your trees. Turf roots compete with tree roots for water and nutrients. All new tree plantings should have a minimum of a 4 foot mulch ring around the tree. Apply mulch 2-4 inches thick but do not apply mulch in direct contact with the tree trunk. Mulch provides many benefits to trees and shrubs. It helps conserve moisture in the soil where it is available to plants. It provides weed control around the plants. Also, it keeps lawn maintenance equipment away from tree trunks. Materials used for mulch include bark, leaves, and pine needles.

Know Your Irrigation System

• Rotary heads deliver a rotating stream of water. Rotary heads are used in lawn areas and can be set to cover 360 degrees around the sprinkler head or adjusted to spray in desired directions to avoid applying water to pavement, driveways, sidewalks and roads. Use a catch-can test to determine irrigation run-time for desired application rate.
• Spray heads are used to water shrub beds, flower beds, and small lawn areas. Spray heads deliver a constant mist of water in a radius around the sprinkler head. Different heads emit a spray of 360 degrees, 180 degrees, 90 degrees, or 45 degrees. Select the right spray heads to direct water away from pavement. Since spray heads deliver a mist of water, they have the greatest potential for water loss during windy conditions. Wind is usually calm during the early morning hours. Use a catch-can test to determine irrigation run-time for desired application rate.
• Drip irrigation systems and soaker hoses apply water directly to the roots. They are the most water efficient systems. Water is applied slowly and virtually no loss of water occurs through evaporation or runoff. To calculate proper run-time of your drip system, turn water on for 15 minutes and dig a small hole next to the drip line or soaker hose. You will see a clear line where the water has soaked into the soil. Check the depth of water penetration every 15 minutes until the water has wet the soil to a depth of 12 inches. Set your timer to run that amount of time.
• Good irrigation systems are designed to provide head-to-head coverage. This means that the spray from one sprinkler head reaches the next sprinkler head. This overlap of watering patterns improves uniform distribution and reduces dry areas due to poor coverage.
• Inspect your irrigation system before you turn it on for the first time of the year to check for leaks and to make sure all heads are adjusted properly.