Tip of the Week — 5/18/09

Posted in Gardening Tips on May 18 2009, by Sonia Uyterhoeven

How to Water Newly Planted Trees

Sonia Uyterhoeven is Gardener for Public Education at The New York Botanical Garden. Join her each weekend for home gardening demonstrations on a variety of topics in the Home Gardening Center.

Newly planted trees are thirsty for water. On the day of planting, give them a deep soaking; then come back the next day and soak them again. The ground around the root ball of the tree will take up most of the water from the first day, and the second watering ensures that the root ball gets soaked.

If you walk around The New York Botanical Garden, you will notice that around newly planted shrubs and trees is a small berm of soil (part of the backfill). What we have done, basically, is to build a saucer around the woody plant that will help retain water.

The saucer should be the size of the root ball. When water is added to this makeshift well, it penetrates into the root ball (and hence the roots) rather than seeping into the disturbed soil around the plant. The berm should be broken down after several months and certainly by the end of the growing season. Distribute the soil away from the tree so that you do not alter the soil level around the root ball

The easiest way for a homeowner to water a newly planted tree or shrub is to lay a hose at the base of the tree and run a slow trickle of water for several hours until the soil is thoroughly soaked. It is better to water your tree once a week with a deep soak than to water it frequently for a short time (which produces a shallow, weak root system).

For additional tips on watering newly planted trees…

For the first year after planting some people like using Treegator® irrigation bags, which can be purchased at a garden center. Water from these bags slowly seeps into the ground around the base of the tree. The directions generally recommend supplying 10 gallons per every inch per caliper (diameter) of the tree. Following these guidelines, a 2-inch caliper tree would require 20 gallons of water per week. These bags should be removed in the fall of the first growing season.

For a homemade alternative, take a large empty soda bottle, fill it with water, and cut several small slits in the side. Lay the soda bottle at the base of your tree—as you would an irrigation bag.

Supplemental watering, of course, is needed only if there is insufficient rain. The guiding rule is that newly planted trees should receive an inch of rain per week during the growing season until they are established. How much is an inch of water?You can pick up a simple rain gauge for about $3 at a garden center or hardware store. If Mother Nature doesn’t supply you the amount of rain you need, place a 1 pint plastic container near the base of the tree and turn on your sprinkler. Time how long it takes for the container to fill up to an inch, and you’ll have a regime set in place.

For how long must you pamper your tree? It depends on the size of the tree. Take a tape measure and measure 6 inches up the trunk from grade (soil level). At that point measure the diameter of the trunk. If the trunk is 2 inches, you will have to nurse the tree for 2 years after it’s planted. If it measures 5 inches, then you are in for half a decade of TLC. For most of your trees and shrubs, 1 to 3 years will be the norm.

Remember that when a tree is young it is putting an enormous amount of energy into growth. This will make any young tree thirsty. Proper watering during its juvenile stages can mean the difference between life and death, so don’t ignore it. Once your tree is established, be vigilant about watering during dry spells in the summer and fall.