The Willamette Valley receives enough rain for most plants in the fall, winter and spring. Our summers are more Mediterranean like and too dry for most plants. New plantings will not survive without regular water and established plants can use some supplemental water during the hot dry spells. Deep watering will encourage deep roots. A deep root system has access to more soil moisture and can survive longer without frequent watering. Allow the surface to dry between watering for most plants. Plants will need more frequent watering with low humidity, wind, high temperatures and long periods without measurable rain.
The first year it is vital to establish a strong root system. Water deeply and often enough so the plant
shows no signs of stress (wilting, dull foliage, burned foliage.) Importantly, the second year the plant should be closely monitored. Water deeply when needed. If you are not sure if the water is getting to the entire root system, check your soil with a shovel (in an area without plants). Dig down and see how far down the water travels. Less water volume for a longer period of time is more likely to go deep to saturate the entire root system. A large amount of water over a shorter period of time will cover a larger area (or run off) and not saturate the soil deeply. Low volume/longer duration can be accomplished with a hose dripping at the base of the plant or low volume sprinkler heads or low-volume drip emitters and a timer. Continue to water even in the winter, if it is dry.
Healthy plants that have been in the ground over 2 years, often will be able to fend for themselves.
However, if needed, water infrequently, deeply and only in the hottest part of the summer. Factors will vary according to type of plant, soil and sun conditions. Continue to water plants under eaves and plants under evergreen trees during the entire year.
Actually a lawn can go without water for long periods of time. An unwatered lawn will usually stay
green for many weeks if not mowed. Lawns which are mostly fescue grass will turn brown when dried out but will quickly recover when fall rains begin. However, ryegrass lawns do not tolerate drying up and turning brown. They will develop bare spots which have to be reseeded. To keep these lawns green, watering every three days for about 20 minutes should do the trick (about 1”/week).
Water alone will only sustain a plant for a limited time. Plants need nutrients to remain healthy, resist
disease and insects and to thrive and grow. After your initial feeding of transplant fertilizer, feed with a slow-release fertilizer twice a year; usually in the spring and late summer. Eliminate weeds that compete for water, nutrients and light, and attract insects and disease. Replenish mulch as it decomposes.