Guide to Watering Your Lawn, Shrubs and Trees

A lush lawn, healthy shrubs and thriving trees require proper irrigation.

Everyone wants a lush, green lawn, healthy shrubs and thriving trees -- and irrigating them properly is key. But how do you know when, where and how much to water? After all, you don't want to over-irrigate your yard, as this can lead to root rot, foliage damage and even plant death.

Plus, over-irrigating wastes a precious resource -- and that's not even mentioning those unnecessarily high water bills. Providing your turf and plants with only the water they actually need may save up to 1,000 gallons per month!

Of course, your climate, soil type, time of year and the types of plants you grow all impact your watering habits. Here's how to determine the correct irrigation placement, amount and frequency for your lawn, shrubs and trees.

Where Should I Water?
Though it may seem counterintuitive, shrubs and trees shouldn't be watered at the trunk. Instead, water should be applied to the plants' "drip line," or the soil that contains the plants' spreading root systems. To locate the drip line, imagine that your tree or shrub's canopy is an umbrella. If rain fell on the umbrella and ran down the sides, where would it land? That zone -- which contains the plants' moisture seeking roots -- is your drip line.

How Much Should I Water?
Different varieties of grasses, trees and shrubs require variable amounts of moisture. Some plants love moist -- or even wet -- soil, while others require well-drained -- or even dry -- soil to thrive. Either way, you want to only provide enough water to penetrate to the plants' root depth.

The best way to determine how much water a plant is getting is by using a soil probe. This slender device slides through wet or moist soil, but can't easily penetrate dry soil. After you irrigate, push the probe into the soil to determine how far down the moisture goes. If it goes farther than the root depth, you're over-watering. If it doesn't make it all the way, you need to irrigate for a little longer.

As a general rule, root depth of mature plants is about:

  • 6 to 12 inches for turf grass
  • 12 to 24 inches for shrubs
  • 18 to 36 inches for trees

Lawn grass should receive about 1 to 1.5 inches per irrigation; figure out how long this takes by placing a couple of containers on the lawn while you're watering and timing how long it takes to get to 1 to 1.5 inches. 

Lawn grass should receive about 1 to 1.5 inches per irrigation.

How Often Should I Water?
The frequency of irrigation depends on the season and on your soil type. During the hot -- dry and windy -- summer months, you'll need to water three to five times more often than during the rest of the year. Plants growing in heavy, clay soil need less-frequent watering than those growing in light, sandy soil. 

As a general rule, water trees:

  • Winter -- twice per month
  • Spring and fall -- once per week
  • Summer -- twice per week

Water shrubs:

  • Winter -- Once per week
  • Spring and fall -- twice per week
  • Summer -- three times per week

As for lawns, you should water when you notice signs of wilt. These include footprints or mower tracks that remain visible for at least 30 minutes, as well as grass that's a blue-gray color. Established lawns may not require watering over the winter, while newly laid lawns will require regular irrigation until they're mature. Remember, it's better to water as infrequently as possible. Not only does this save water, it stimulates deep root growth for healthier plants.

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