By PAUL HETZLER
Transplanting a tree during the growing season is kind of like having surgery without anesthesia. It can be done, but it causes a lot of undue stress. While conifers should only be dug and moved in early spring, fall is a great time to transplant hardwoods. Once the leaves are off, trees can be successfully moved because they’re dormant, dormant being the French term for “sleeping so deep that you don’t awaken even if someone digs you up by the roots.”
Actually, no matter what time of year you're planning to dig up a tree, October is the ideal time for a treatment that will ensure you get a stronger, healthier root system. Or at least that your tree will. More on that later.
Most authorities, except those trying to sell you a large tree, will tell you that small trees recover from transplanting faster than large trees. In fact, small trees often overtake larger ones planted at the same time. This can work in your favor, since moving a small tree is easier on your back.
Whatever size tree you have in mind, digging a wide root ball is much more critical than getting a deep one. Ninety percent of a tree's roots are in the top ten inches of soil. To reflect this fact, the ideal planting hole is saucer-shaped, two to three times as wide as the root system, but no deeper. The flare at the base of the trunk should be visible after planting.
In a natural environment, tree roots extend more than twice the branch length. This means when we dig our little circle (based on what we can reasonably lift) around the tree, we cut off the majority of the root system. Which is where that root treatment comes in.
Go out right now—or fairly soon, maybe after you finish your coffee—and dig straight down in a circle the size of the intended root ball. A flat-bottom spade works best. Given what I've just said, this root pruning may seem like a bad idea. However, during the period of color change, trees move a lot of sugars from leaves, twigs and branches down into the roots. By cutting the roots you'll ensure that hereafter, all sugars the tree moves will get stored within the root ball. Not only that, but fine roots are stimulated to grow within the root ball, creating a more robust root system.
Adding gobs of organic matter to the backfill likely dates back to ancient times, when people might grab an arborist, if one was handy, and throw them in the planting hole. Possibly in response to this, arborists these days recommend little or no additional organic matter, depending on soil conditions. When planting in construction fill or straight sand, though, soil may be amended with up to thirty percent organic matter. No fertilizer should be used at planting time, or within the first year.
Roots continue to grow until the end of December, so don't let your new transplant dry out too much. Mulch about 1” deep at planting, and then add another 3” in late spring. Keep the mulch pulled a few inches back from the trunk. And unless you have reason to believe your hardwood tree is some kind of vampire, don't stake it. (Large conifer transplants, though not known to be vampires, may require staking.) Movement is needed for strong trunk development.
Happy planting, and please—no arborists in the backfill.
Paul Hetzler is a forester and a horticulture and natural resources educator for Cornell Cooperative Extension of St. Lawrence County.