A new landscape is more susceptible to disease and insect problems, because plants are weakened, and root systems are not well established. Correct watering and control of diseases and insects helps the new landscape thrive during its first important season.
Water, but not too much and not too little. It’s difficult to recommend a standard “one-size-fits-all” watering program because of variations in soil conditions, natural precipitation, temperature and a plant’s moisture needs. Each situation is different. Overwatering, however, probably is the most common cause of death for newly transplanted trees and shrubs.
Generally newly planted trees and shrubs should be watered immediately after planting. For the next 2 weeks at least, be sure your new tree material gets a minimum of 1″ of water every other day. After your plant is established, you will need to supplement its water schedule for the first year. Using 1-2″ of water every 4 to 7 days should be adequate, again either by rainfall or hand watering.
Learning to identify and understand the growth habits of your trees can be very helpful. This may take several seasons, but you will be able to notice any unusual changes in your trees and take action to correct problems before they become severe. Newly planted trees require 2-3 years for their root systems to become fully established. During this time extra watering and special care are necessary.
The best way to water your trees and shrubs is the slow-soak method. Although the big stream may be the most personally satisfying, a deep watering over an extended period (like a slow-drip from your hose overnight) is the best way. This will allow the moisture to go deep to the bottom of the roots. The majority of the water-absorbing roots are in the top 18″ of ground.
Following the first two weeks after planting a simple test can help the new gardener determine when to water. Until you know from experience, dig carefully six to eight inches near the root zone, and squeeze a handful of soil. If it is damp enough to form a ball, no water is necessary. If it falls apart easily, water. Don’t worry if the top few inches are dry. Roots need air almost as much as they need moisture. Frequent watering saturates the soil and suffocates the roots. Encourage maximum plant growth by deep but infrequent watering.
Watch trees and shrubs, especially those near lawn sprinklers, for over-watering stress. Leaves may yellow and wilt, just as if they lacked water.
New plants need little, if any, pruning during their first season, but pruning needs may increase thereafter.
It’s not necessary to fertilize new shrubs after planting; doing so may burn new plant roots. Soil, improved at planting time, usually will supply a plant’s nutritional needs the first season. After the first year, fertilize after leaves emerge, but before mid-July. Avoid late-season fertilization; this encourages late, soft growth that is subject to winterkill.
Watch for insect and disease problems. Correct diagnosis and identification is necessary to determine effective treatment. Become familiar with the most common problems specific to each plant, for example, black leaf spot on aspen and spider mites on junipers.
Mulch root zones to reduce temperature extremes and to decrease fluctuations in soil moisture. Mulching helps shallow-rooted young plants survive the winter.