When to water trees and shrubs
Watering frequency depends on the type of plant, the soil texture, whether you are caring for an established or a new plant, and local weather conditions. Learn the specific water requirements of your plants, monitor local weather and soil conditions, and water accordingly.
For newly-planted trees and shrubs:
Water immediately and thoroughly after planting.
For the first 2 weeks after planting, check the soil moisture daily and water deeply if the top 6 inches of soil feels dry to the touch.
During the first two years after planting, check the soil moisture at least once a week and water if the soil feels dry at 6 inches. This is especially important to help the roots of new plants get established in the soil.
Be careful not to overwater. Many people have inadvertently drowned newly planted trees by watering them too often. Water should soak in quickly; your plants should never sit in a puddle of water for an extended period of time. This can lead to root damage.
For all trees and shrubs:
Water when the soil feels dry to the touch beneath the surface. Dig into the soil with a trowel, hand shovel, or screwdriver and check your soil at a depth of about 6 inches. Soil that is moist or damp to the touch is fine. If the soil feels dry, water the plant thoroughly. Direct water to the roots, not the leaves of the plant.
Water in the morning. Watering during the heat of the day increases the amount of water lost to evaporation by as much as 40%. Late-day, overhead watering increases the chances of some plants being infected by diseases.
Observe how quickly your soil dries out after rain or watering. Clay soil drains slowly porous sandy soil drains quickly. Adding organic matter to the soil will improve drainage in clay soil and increase water retention in sandy soil.
Evergreens – trees or shrubs that have needles or leaves that remain green on the plant through the winter – should be deeply watered in the fall before the ground freezes if precipitation has been insufficient. Evergreens continue to lose water during the winter, especially when the temperature is above 40°F and on sunny, windy days. If the soil is dry, the plants may become desiccated, turn brown, and die, even if those symptoms don’t become obvious until spring.
Watch summer and fall weather conditions:
Check soil moisture at least weekly during the hottest, driest part of summer and fall when plants have a higher demand for water.
Extended periods of drought can negatively affect most plants. Prioritize watering young trees, then shrubs, then herbaceous plants (those with soft stems). Large, mature shade trees and shrubs can be left alone unless the drought is severe or the trees begin to wilt or the root systems have been recently disturbed.
How to water trees and shrubs
- Water deeply so the water penetrates the top 6 inches of soil.
- Deep and infrequent watering is recommended because it encourages a deep root system and makes plants more tolerant of droughts. Frequent, light watering encourages shallow root growth and less tolerance for dry conditions.
- Apply water over as much of the root area of your plant(s) as possible. The root zones of trees and shrubs extend out from the trunk at a distance at least equal to the height of the plant. Focus watering near the drip line of your plant’s canopy where feeder roots are located. Applying water just around the base of a trunk does little good and can lead to decay.
- The most efficient method is to apply water directly to the soil by running a hose at a slow trickle around the roots of your plant. Or, use a soaker hose or drip irrigation.
- Drip or trickle irrigation is one of the most effective and water-efficient methods of watering. The system discharges small quantities of water on a regular basis directly to the root zone under a tree or shrub. Very little water is lost to the air through evaporation.
- Tree watering bags placed at the base of newly planted trees and shrubs provide a slow method of delivering water to the roots. They are often used by commercial landscapers but are available to retail customers as well.
- A five-gallon bucket with a few small holes drilled into the bottom will work similarly to a tree watering bag. Fill the bucket and allow the water to trickle onto the root area slowly.
- Sprinklers can be portable and moved around the landscape as needed or they can be permanently-installed systems. The uniformity of watering depends on the type of sprinklers used, water pressure, and wind conditions. Closely monitor watering patterns to make sure targeted plants receive adequate water and to check that water is not running onto hard surfaces like sidewalks and driveways where it will be wasted.
- Overhead watering by showering the foliage can increase disease problems especially if the water sits on the leaves for a prolonged period of time. For example, overhead watering promotes black spot disease on roses and Cherry Shot Hole infections on cherry laurels.
How much water?
- Wetting the soil at least 6 inches deep requires 1 to 2 inches of surface water (65-130 gallons of water per 100 square feet). The amount of water depends on soil type, weather, and types of plants growing.
- If you use an overhead sprinkler, check the amount of water the sprinkler is providing to a group of plants by placing a tin can in the range of the sprinkler. When 1 inch of water accumulates in the can, 1 inch of water has been distributed in the soil. This is enough to penetrate 6 inches of soil.
To check the effectiveness of watering: Wait at least four hours for the water to percolate in the soil and then check the moisture level at 6 inches deep by probing the soil in several locations using a hand trowel, screwdriver, or spade.
Mulch plantings (no deeper than 3 inches) to reduce the need for watering during dry spells. Mulches keep soils cool and reduce water loss through evaporation.