by Michelle Sutton
Trickles are Better than Sprinkles, and Other Watering Advice
Newly planted trees need more localized water. You will frequently encounter the guideline that plants need 1 to 2 inches of water per week provided by some combination of rainfall and hand watering. That is great for established trees, but newly planted ones have special challenges. For the first season, until the tree’s roots start to grow and explore the surrounding soil environment, the tree has to get all its water needs met from the existing little ball of roots. You will find that even in rain-moist landscapes, the newly planted trees can be stubbornly dry, even to the point of wilting.
Saturation of the root ball is essential to allowing roots to grow and is best achieved by deep soaking by hand, by irrigation bags, or by drip irrigation. You can put an open-ended hose on the surface and let it trickle for half a day or more. Or if you have the time, you can relax into a hand-watering session, backtracking to pay multiple visits to the tree to give the water a chance to really infiltrate the root ball—not just run off into surrounding soil.
Amending the planting site generously with organic matter helps, too, because organic matter improves a soil’s water holding capacity.
Established trees and shrubs need watering during extended dry times. Pay extra attention to newly planted trees and shrubs for the first three years (as that’s how long it takes most to successfully survive transplant shock and start to establish). Then they are pretty much on their own—unless it is a very dry summer, and either the plant is showing symptoms of water stress, like pale or wilting leaves, or you can simply see how dreadfully dry the soil is, or you just want to ensure the plant’s long-term health. Often when plants show signs of drought stress, large sections of the plant may already be dying, and it’s not uncommon for the effects of this summer’s drought stress to show up next summer. For established shade trees and other woody plants that you value, consider the open-ended hose slow trickle for a day a week during drought times.
Keeping plants mulched helps a lot. Another way to protect those established trees from water stress is to use 2 to 3 inches depth of mulch, for as far out as you can reasonably go. Besides moisture retention, providing mulched areas around trees keeps lawn mower and foot traffic off tree roots and protects tree trunks from mechanical damage from mowers and weed whackers.
Water less frequently but more deeply. Thorough wetting of the soil done less often does more good for plant roots than frequent, shallow watering. More water actually percolates to roots, and it encourages roots to explore a greater volume of soil.
Water is the best fertilizer. Examining a hedge that was looking pale, I immediately jumped to “must need fertilizer.” But on reflection, I realized that water stress could produce the same effect on the leaves. I did a little experiment on the hedge, whereby one half I fertilized and watered deeply, and the other half I watered deeply but did not fertilize. The latter greened up just as nicely. So much of the magical greening that people attribute to fertilizer is really courtesy of the attentive watering that accompanies it. Indeed, most fertilizers are salt-based and can contribute to plant root desiccation. So try “fertilizing” with deep watering first. 🌳