Proper watering throughout the first year often means the difference between success and failure. After planting, build up a slight berm, about 3-4 inches high, around the planting hole to aid watering and prevent runoff. On a sloping site, leave the upper side of the saucer open to catch surface water as it moves downhill.
In an average loam soil, spring-planted trees and shrubs should be soaked once a week if there is less than 1 inch of rainfall. Water more often in sandy soil. In heavy loam or clay soil, a good soaking every 10 to 14 days should be sufficient. Continue watering to supplement rainfall during the fall and winter until the soil freezes. Many fall-planted trees and shrubs are lost because of inadequate moisture, especially evergreens that are exposed to drying winds. Regular watering should be continued in the tree’s second growing season.
How much water a plant will need varies greatly as to type of plant, whether it is established or newly planted, the weather conditions, the wind, the soil type, the soil drainage and more.
For almost all plants, a deep soaking followed by enough time for the soil to dry out slightly is ideal.
Frequent light watering is not good for plants. It encourages shallow root growth. That's why irrigation systems designed for the lawn are seldom adequate for landscape plants and if they aren't set up and operated properly, they can actually be harmful to a lawn too.
Feel the soil before watering and don't be deceived if the surface is dry.
The outward signs of too much water are wilting and yellowing of leaves, especially those in the inner areas of the plant.
Whenever possible, plants should be watered early in the day.
The amount of irrigation water that falls on a given area can be measured by setting out several shallow, straight-sided containers such as tuna or cat food cans.
Mulching with an organic material such as shredded bark minimizes evaporation and weed competition, thereby minimizing the amount water you will need to provide your plants.
Avoid sprinklers that put out a fine mist. Too much is lost to evaporation.
Avoid watering directly from a hose. Average soil can only absorb about a half inch an hour.
Native plants usually require less water than non-natives and exotics.
Healthy plants need less water than stressed plants.
Bluegrass needs to stay evenly moist to do well. But if you have a lower-maintenance lawn with fine fescue and perennial rye, an inch a week will be much more than the lawn needs for health.
Frequent, shallow watering encourages poor turf root development and often leads to bare spots and disease prone grass.
In average soil, established trees and shrubs need an inch of slow rain every two to three weeks.
Newly planted trees and shrubs need an inch of water every week, ideally split between two waterings.
The majority of the roots that absorb water for an established tree or shrub are outside the dripline where nature would provide rain. That is where you should water, not under the canopy.
Plants need more water during the first half of the growing season than they do later in the season.
Plants that fruit, such as apple trees, need more water while fruit is developing.
Vegetables need about an inch of water each week.