Gardeners will be planting more trees than ever this coming spring as we try to make a difference in the amount of carbon dioxide released into the atmosphere. For first-timers, however, there ought to be a “New Tree Purchasing and Planting Guide” at the local garden center, a recipe for success.
It might read as follows: “We sell only small trees, 2 inches or less in trunk diameter. Research on tree growth tells us that smaller trees replace roots damaged during handling faster than larger trees. A 1- to 2-inch caliper tree will replace those roots within two growing seasons and, during the next 10 years, outgrow a tree purchased with a greater trunk diameter. Smaller trees also reach maturity with less branch dieback than larger trees.
“If we could, we would offer only naturally grown trees that have not been nursery-pruned. Unfortunately, the standard in the nursery industry at present is to prune the leader of a tree as it grows to encourage production of lateral branches spaced only inches apart along the trunk. This is done to increase sales, but imagine the problems for the tree if all of these closely spaced branches were allowed to remain, growing larger in diameter every year!
“Generally, branches selected for removal should be pruned off before they reach one-quarter inch in diameter so that pruning wounds will heal quickly. Remove these and larger limbs when you plant your tree; smaller branches can be removed in subsequent years until the desired scaffold branching system is achieved.
“We will be happy to get you started in the process of pruning excess branches from your new tree, showing you the proper pruning cut to use. We also can suggest the final spacing of permanent scaffold branches on your tree, a factor that depends on the species.
“The planting hole for your new tree should be at least twice as wide as the tree’s root ball, but no deeper. DO NOT amend the backfill soil removed from the planting hole. Research shows that adding organic matter to the backfill inhibits new root growth beyond the hole, resulting in a root system that circles the outer perimeter of the planting hole rather than growing outward. (The one exception to this rule is for native soils that are extremely sandy or clayey, in which case amending the soil no more than 25 percent by volume with organic matter is acceptable.)
“Plant your new tree at the same depth that it was growing in its container, no deeper. Add the backfill a few inches at a time, watering each addition well to eliminate air pockets around the roots. Never stomp on the soil after filling the hole! This compacts the soil and breaks off roots.
“Mulch the soil around your new tree after planting, but DO NOT pile mulch around the trunk, an often-seen mistake that can lead to trunk rot. Shredded bark, shredded leaves or compost make good mulches that should be renewed every year in an ever-expanding area around the growing tree. Minimally, you should keep the root zone mulched out to the canopy drip line, preferably twice as far.
“During the establishment period (one year for each inch of trunk diameter at purchase), your new tree should receive an inch of water every week during the growing season, either from rain or irrigation, over the entire root area.
“DO NOT fertilize your tree during the establishment period. Fertilizing spurs shoot growth and, remember, you are trying to encourage root growth during the first year or two.
“Fertilizing established trees is typically not necessary in a healthy landscape. Ample nutrients should be available for moderate tree growth if mulch is replenished every year and nutrients are not removed by collecting falling leaves. Compost your leaves and use the finished compost for mulch!
“Your goal should be moderate growth, not the fast growth that results from excess applications of nitrogen, growth that is particularly attractive to insects and disease organisms. Trees planted in lawns that receive excessive levels of nitrogen and water are particularly vulnerable.
“Good luck with your new tree!”
You very well may be given a document like this where you buy your trees. But just in case, keep this column folded in your pocket when you go shopping.