Our seasonal dry period in the Pacific Northwest usually starts in June and we need to irrigate to keep plants green and growing. Automatic sprinkler systems are often set to water a few minutes every day. This only keeps the soil surface moist, encourages weed seed germination and does not reach the deeper roots. At least one half inch of water should be applied each time you irrigate. Then the surface soil should be allowed to dry out between irrigations. Lawns, flowers, and vegetables may need irrigation once every two or three days during hottest weather. Shrubs and trees usually will go a week or longer between irrigations. If you are not sure how long it takes your sprinklers to apply a half inch of water, place cans, such as tuna fish, in several areas. Different kinds of sprinklers and sprinkler heads apply water at different rates.