When to Plant Trees

tree-planting-guide-diagramFor most trees, fall is the best time to plant. The soil is warm but not waterlogged the way it can be in spring, and trees without leaves make fewer demands on their roots to provide nutrients.

A few trees, however, including magnolia, birch, hawthorn, black gum, tulip tree, and most oaks, get downright cranky when planted in the fall. No one knows for sure, but researchers think that there is something that prevents the root structure from taking up enough water to overcome transplant shock, and that winter comes before the tree is ready for it.

Studies by Dr. Nina Bassuk at the Cornell University Urban Horticulture Institute in Ithaca, New York, show that transplanting these trees when they are smaller increases the success rate for fall planting. She has had much better results with trees that measure less than 2 inches in diameter at a point 6 inches above where the trunk emerges from the roots than she has had with larger trees. Be sure to water that new tree in well. Whether it has leaves or not, it needs water.

Watering also settles the soil and helps eliminate any air pockets. Dormant trees planted in October or early November should need only that one deep, soothing watering to last them the winter. But all that said, it is still better to plant magnolias in spring.

Like other things in life that aren’t what they used to be, burlap has changed. Whether for the better depends on your point of view. A single layer of plain old untreated burlap, now almost a thing of the past, rots away nicely and lets roots wander freely out of their soil ball. But you are just as likely to run into a plastic burlap-like material, or into burlap that has been treated with a rot-resistant chemical.

Both are popular in the horticultural industry for the same reason: they stay intact longer, through sunshine and waterings, as the tree makes its way from its growing site to you. But that perseverance presents problems for growing roots trying to find their way into new surroundings. Rot-resistant burlap takes years longer to decay than untreated does, and even untreated burlap presents a formidable boundary if wadded down in layers and left in place.

In both cases, these barriers restrict the diameter of the roots as they grow out. In some cases, the tree may even die. At that point, you can dig it up and use the original wrapping to take the dead tree to the dump.

To avoid such problems, after placing the tree in that nice extra-wide-but-no-deeper-than-the-ball hole, untie the twine around the trunk and cut away the burlap.

Note: some ideas are harder to kill than crabgrass. One of them is that when a tree is dug up to be sold, the branches should be removed to compensate for the loss of roots. The rationale is to balance root loss with the removal of an equal amount of top growth. The tree is then thought to be better balanced and better able to withstand transplant shock.

As logical as this sounds at first, it just doesn’t hold up. The human equivalent might be removing the right arm of someone who has just lost her left leg in an accident.

Transplanted trees need all the food they can produce to support the regrowth of those lost roots. The food comes from leaves doing their thing, so the more leaves, the better. The only branches that should be pruned are those that are dead, diseased, damaged, or rubbing against other branches.

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