Planting a tree isn’t rocket science, which is good thing. If it were that complex, I’d wager we’d have a lot fewer trees lining our streets. It may not take a scientist to plant a tree correctly, but a lot of money is spent each year to buy and plant trees which may as well be leased, because they will only live a fraction of their expected lifespan.
When trees decline and die after 15, 20, or even 30 years, the last thing we probably suspect is shoddy planting. Although landscape trees like mountain-ash and birch have naturally short lives, a sugar maple or red oak should easily last a hundred or more years. Yet all too often, a long-lived species will expire at twenty because it was planted “fast and dirty.” You can find examples of trees declining as an age-class in housing developments, and especially along NYS routes where DOT low-bid contractors replaced trees cut down for road improvements. One may as well consider such trees rentals, not purchases.
Deep planting sets the stage for a sickly tree headed for an early death. Every tree comes with a handy “depth gauge” called the trunk flare, which should be visible above the original soil grade. If the trunk looks more like a fencepost where it goes into the ground, the tree has been planted too deep.
Given their druthers, tree roots extend 2-3 times the branch length, or drip line. When a good-size tree is dug in the nursery, between 80 and 90% of its roots are cut off by the tree spade used to dig it. The term transplant shock refers to this catastrophic loss of roots. Obviously, trees can and do survive transplanting, but they need to get their roots back. Initially, a good deal of root re-growth happens within the root ball. Fibrous roots proliferate in the original soil plug, and for a time the tree is much like a potted plant even though it may look like it has a world of room.
When a transplanted tree begins to send out roots from the root ball, it’s essential they be able to penetrate into the soil around it. Any barrier, no matter how slight, can induce a root to turn aside in search of an opening. Barriers include compacted soils—a common condition in road rights-of-way—as well as heavy clay, stones and other buried objects. Even the burlap around the root ball has been shown to cause roots to circle around inside the fabric. To make matters worse, much of the burlap used today contains synthetic material which does not break down. Wire cages surrounding the burlap can last decades, and often cause further problems as roots enlarge.
Over time, tiny circling roots become large circling roots. As they increase in diameter they constrict one another. If the wire cage is left on the root ball, roots more frequently encounter wires as they thicken and lengthen, which cause further cutting and constriction. Circling roots near the surface eventually become girdling roots which begin to strangle the trunk, either partially or wholly, below the soil line. This cuts off water and nutrients to part or all of the crown, and stress symptoms like early fall color and twig dieback appear.
If you would like to learn how to plant trees that your grandchildren can point to with pride, please join St. Lawrence County Soil and Water Conservation District and Cornell Cooperative Extension on Saturday, October 13 from 9 am to 12 pm in Canton’s Bend-In-The-River Park at 90 Lincoln Street for a workshop on tree planting and care.
The class is free and open to the public, but pre-registration is requested. To register or for more information, call the Soil and Water Conservation District at (315) 386-3582.
Paul Hetzler is a horticulture and natural resources educator with Cornell Cooperative Extension of St. Lawrence County.