Thursday, August 18, 2022
Aug. 18, 2022

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Gardening With Allen: Water right for healthy lawn


I tried to keep my lawn green last summer by daily irrigation. Some areas went brown anyway. Would fertilizer help keep it green? How often do I need to water my other plants?

Two weeks ago, it seemed like the rain would never end. With the recent warm, dry weather, plants need irrigation to keep them green. I am on a three-day schedule except for newly planted plants. Most container-grown plants were watered daily until we put them into the ground. So daily watering is necessary when first planted. When established, most pots, tubs and baskets will go two days between irrigations. However, when temperatures get into the 80s and 90s, plants need daily watering.

Lawns usually have a good deep root system going into summer. If you water long enough to get the whole root system wet (to a depth of 4 to 6 inches), lawns can often go three days between irrigations. Daily light irrigation will probably only wet the top inch of soil, so that is where the grass roots will grow. You need to apply a half-inch of water at each application to reach 4 to 6 inches deep. A simple way to measure water application amount is to place shallow tuna cans on the lawn. Place cans in dry and wet areas. Run sprinklers for a specific amount of time, such as 20 minutes, and measure the accumulated water. This will help you determine how long to run the sprinklers.

Shrubs and trees need less water than lawns. If grass and beds have separate irrigation zones, they can be watered different amounts or intervals. However, most sprinkler systems do not have them separated, so the lawn determines the amount and frequency of irrigation. If you install or modify your irrigation system, design it so beds are irrigated separately from lawns. Drip irrigation is effective for irrigating shrubs and trees. By eliminating evaporation loss, water use is reduced by half. Drip irrigation can also be installed for tubs and baskets, eliminating the need for frequent hand watering.

The predominant grass used for sodding or seeding new lawns in the Pacific Northwest is ryegrass. With irrigation, it will remain green during the summer. Most lawns have a mixture of grass types. Several native grasses invade lawns over a period of years. Birds and wind carry in seeds that sprout and grow. Some grasses are moved by mowing equipment from one lawn to the next. Small pieces of grass stems get stuck in mowers and drop onto the lawn. During the rainy season, when soil is constantly wet, these pieces of stem can sprout roots and grow. Some native wild grasses are programmed to go dormant and brown during the summer, even if irrigated. So success in keeping your lawn green with irrigation will depend upon which grasses are in your lawn. Without irrigation, ryegrass will also become dormant and brown.

It is all right to fertilize your lawn during the summer if you avoid applying it when the temperature is likely to be over 90 degrees. It is important to irrigate immediately after fertilizer application so granular fertilizer is washed off the leaves and into the soil. You can apply a liquid fertilizer at reduced risk during hot weather. However, even liquid fertilizer should be followed by irrigation. Weed and feed products should not be irrigated right after application because it washes the weed killer off the weed leaves. Another way to make summer fertilizer application safer is to apply at half the normal rate. Lawn fertilizer will help keep ryegrass greener during the summer. Some native grasses will turn brown even with summer fertilization.

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