Tree Planting Tips

Posted: April 20, 2012

Let’s say you want to plant a tree this spring. Perhaps the beauty of spring-flowering trees has inspired you, or perhaps you need to replace a tree damaged by the Halloween snow last fall. But do you know the right way to plant a tree?

You may be surprised to find that it’s not what you may have been taught. Consider the following statements – true or false?

·        For the quickest shade, buy the biggest tree you can afford.

·        Dig the hole twice as deep as the root ball.

·        Don’t disturb the root ball when planting or you may damage the roots.

·        Improve the soil in the hole by mixing in a generous amount of organic matter.

·        Add a mound of mulch around the trunk to protect it after planting.

·        Cut back the crown of the tree by 1/3 after planting to compensate for lost roots.

ALL of these statements are false, and yet many repeat them as time-honored tradition. Research has proven otherwise. If you want a tree to survive and thrive, follow these suggestions instead:

·        Smaller trees – up to about 6 feet in height or up to about 1-inch caliper – are much easier to transplant and will re-establish much more quickly than a larger tree in a small container, which is likely to have a very poor root system. A larger tree may suffer transplant shock for 5-10 years, during which time a smaller tree will have surpassed it in growth rate and size.

·        Dig a shallow hole that is 2 to 5 times wider than the root ball. You must find the root flare first, and dig the hole only deep enough to position the root flare at or slightly above soil grade. The root flare is that widening of the trunk at its base to join the roots; it may be buried or hidden within the container mix or ball of soil. The root mass should be resting on undisturbed soil, and your planting hole should be a wide, shallow bowl, not a deep narrow cup.

·        Do give the roots a “bad hair day”! It is important to loosen and examine the roots of a container-grown tree before planting. Kinked, girdling, damaged, defective, and very long roots should be trimmed. This does not harm the plant; it will encourage the growth of healthy new roots and may prevent the future problems of a poor root system. When working with roots, keep them moist and shaded at all times. On a balled-and-burlapped tree, all twine and burlap should be removed, and as much of the wire basket as possible. Do remove enough of the soil ball at the top to find the root flare, but you don’t need to break up the rest of the ball unless there are circling roots.

·        In average garden soil, do not amend the backfill soil with organic matter. Loosen it and break up large clumps before backfilling around the roots. If the soil is extremely poor, mix up to 10% by volume of organic matter into the backfill. Amending the backfill soil with copious amounts of organic matter (compost, manure, or peat moss, for instance) changes its texture, which makes it very difficult for the roots to grow beyond the planting hole. A strong tree will have roots spreading outward into native soil, not circling within amended backfill soil.

·        Do not mound mulch up around the trunk of a tree. This is called a “mulch volcano,” and we all know that trees don’t grow in volcanoes. Mulch should be applied in a thin flat layer, 3 to 4 inches thick, spread over as much of the root zone under the tree’s canopy as you can manage, with an area left bare directly around the tree’s trunk. Mulch piled right against the trunk keeps the bark moist, which can lead to insect and disease problems; it  also provides habitat for nibbling animals such as mice and voles; and can lead to girdling roots by interfering with oxygen and water absorption by the roots.

·        Newly transplanted trees should not be pruned to ‘balance’ the crown and roots. The leaf canopy provides energy to the roots to help them begin growing. Pruning stimulates the tree to expend energy on new top growth at the expense of root growth. The only pruning that should be done at planting is to remove broken, dead, or defective branches. Give roots at least one year to become established before pruning the tree for structure.

Once your tree is properly planted, continue to keep it watered (moist but not saturated soil throughout the root zone) for at least the first year after transplanting. These guidelines, more than any transplant potions or out-dated advice, will ensure a healthy tree for the long term.