Watering New Trees and Shrubs
Not too much, not too little
Many home gardeners plant trees and shrubs only to lose them to improper watering. For instance, you do not need to water newly transplanted plants daily. By doing so, you are drowning the roots and killing the plants.
If the plant was container-grown, the roots are contained within the root ball. If the plant was balled and burlaped or bare-rooted, it has lost up to 90 percent of its roots and must generate new ones ASAP to become established and survive. No matter how you bought it, you need to irrigate the plant enough to keep the root system active but not so much as to exclude oxygen from the soil surrounding the roots.
White pine Christmas tree shearing has stared, and I am already seeing young bagworms one-eighth to one-quarter-inch long clinging to the needles, mostly at the top of the trees. If you had bagworms on your pine, spruce, arborvitae and junipers last year, you will have them again this year. Now is the time to wipe them off the needles. You can do it with your gloved hand, and let them lie where they fall.
Roots need oxygen. When you water plants daily, the water excludes oxygen from the soil. Roots that have been damaged from being dug and transplanted have a higher demand for oxygen than roots that are well established and well distributed. This is equally true of container-grown plants even after slashing their root balls to disrupt their circular growth and force new roots to grow into the surrounding soil.
Generally, a good heavy watering two to three times a week provides sufficient moisture to satisfy the needs of the roots for both water and oxygen. Daily light irrigation does not provide adequate moisture to the deeper roots and excludes oxygen from the roots near the surface. If you’ve planted in a soil that is not well drained, watering once a week may be adequate.
As soon as you see that the plant is starting to generate new growth, reduce the frequency of irrigations. Root growth is accelerated by wetting and drying soils. Frequent light irrigations encourages shallow rooting, thus making the plants less drought-tolerant. Deep and thorough irrigation encourages the roots to grow deeper in the soil, where there is greater abundance of water.
Giving trees and shrubs an abundance of water from mid-August to mid-September also assures better winter survival.