City Trees

Construction, digging, or staging area nearby? Make sure your tree has a large tree protection zone. The tree protection zone is at least as wide as the tree canopy, but preferably much wider. If you can't accomplish this, work with an ISA Certified Arborist on ways to minimize mechanical damage to the tree and root compaction by equipment. Now that you can visualize the plate of fine roots that grow so close to the surface, you can see why you don't have to dig very deep in order for real damage to occur. Excerpt from Part 4: Advice on Watering The practice of watering trees seems like it should be pretty simple, but there are some simple techniques that make a big difference. 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 com- bination 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 envi- ronment, 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 paying multiple visits to the tree to give the water a chance to really infil- trate the root ball—not just run off into surrounding soil. 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 trans- plant shock and start to establish). 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. 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 encour- ages roots to explore a greater volume of soil. Water is the best fertilizer. Years ago, examining a hedge that was looking pale, I immediately jumped to "must need fertilizer." But water stress could produce the same paleness. I did a little experiment on my cli- ent's 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. "Trickles are better than sprinkles" is one key piece of watering advice. 36 CityTREES

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