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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

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October 2002

Anchoring roots the right way

Pay attention to planting details today if you want a big tree tomorrow.

Tracy Salisbury

Which tree to plant?
Preparing the site
Planting the tree
Caring for your tree

The way you plant a tree will make all the difference in its health, beauty and function over a lifetime – which could be a hundred years or more. Plant properly and you'll be rewarded for decades.

Which tree to plant?

Plant the right tree in the right place! Start by gathering information about the planting site. Your decision should be based on four criteria:

  • Size: The tree must have enough space to expand to its mature size above and below ground. Be sure trees are not planted on or near property lines. Their mature size may extend beyond the boundaries. Allow adequate spacing between trees and vegetation avoids conflicts. Check the site for obstructions such as overhead wires, buildings, or pavement, and be sure to call the statewide Diggers Hotline at (800) 242-8511 to locate underground lines. Do not expect that pruning will keep a tree within bounds. It won't! When large-growing trees are planted under utility lines, excessive pruning is required to keep the tree from obstructing the lines. This type of pruning may lead to hazards and eventual tree removal. Low-growing trees are available and can be planted successfully under utility lines.

  • Needs: Each tree species has specific requirements for soil type, pH, moisture drainage and sunlight. Review your site carefully and narrow the list of species to those that can prosper under your site conditions.

  • Diversity: So what if everyone on the block has Norway maples in the back yard! Spend a little time identifying the trees in the immediate area and select species for your property that will add diversity to the urban forest. Some communities have ordinances restricting planting of certain tree species. Check with local officials before purchasing your tree.

  • Landscape: You should consider the role you want the tree to play in your overall landscape plan, but this shouldn't be your sole criterion for choosing a particular species. Thousands of trees die every year when design and aesthetics are placed ahead of biology.

Once you have decided which species to plant, carefully select a healthy, well-shaped specimen at the nursery. Poor form or other problems may worsen as the tree grows larger, so take time and choose wisely now.

Preparing the site

For many years, we've been told to plant trees at the same depth as they were in the nursery. Nursery practices, often lead to three to 12 inches of excess soil heaped on top of the roots. Planting the tree at this same depth may lead to problems later in the tree's life. These may include trunk cracks and root rot, crown dieback and possibly girdling roots and premature tree death.

To determine the correct depth of the hole, measure the depth of the root system from the root collar to the bottom of the root ball. The root collar is the point where the roots and trunk meet. It is most easily recognized by a flaring at the base of the trunk. (Do not confuse the root collar with the bud graft, a swelling of the trunk on some plants where a scion was grafted onto the rootstock. The bud graft is usually about four-six inches above the root flare.) When working with potted, containerized, or balled-and-burlapped plants, remove the soil to expose the root collar.

Dig the hole slightly shallower than the depth of the root system, and three times as wide. Leave an undisturbed mound of soil in the bottom for the tree to sit on. Taper the sides of the hole and use a shovel to rough up the exposed walls. Using a rototiller, shovel or spading fork, loosen the soil over an area outside the hole at least three to five times the diameter of the root system and eight inches deep. If the soil is compacted, loosen it up even deeper.

Planting the tree

At the nursery, tree stock comes in three types:

  • Bare root: Because the roots have no soil on them, they must be kept cool and moist at all times. Before planting, inspect the roots. Damaged or broken roots should be clipped using sharp hand pruners. Spread the roots out as you set the tree down on the mound. The root collar is plainly visible to judge proper depth. Bare root trees should be planted when dormant.

  • Potted or containerized: Cut and remove the container first, then carefully set the tree in the hole. Cut any large roots that encircle the outside of the root ball using sharp hand pruners. If the root collar is not visible, dig down until it is and remove excess soil from the top of the root ball. Grow bags are another option and fairly new in the Wisconsin nursery industry.

  • Balled-and-burlapped: Remove the twine around the trunk, peel the top of the burlap back and check for the root collar. Carefully set the tree at the proper depth without disturbing the ball, then remove excess soil from the top of the ball. Snip as much of the wire basket off as possible and peel the burlap at least half way down the sides of the ball so roots can expand into the native soil without restriction.

Whatever type of planting stock you're working with, place the root collar even with the soil surface, or one to two inches above grade. It's better to plant on the shallow side, because newly planted trees often settle a little. Plumb the tree and you're ready to begin backfilling.

Use the soil removed from the hole as fill. Don't use new or amended soil because it can disrupt soil water movement. Break up large clumps of soil and discard large rocks and other debris. As you shovel soil over the tree roots, don't pack it down. Water and gravity will settle the soil naturally. Refill any air spaces that are caused by watering.

Caring for your tree

It's best not to fertilize at planting. Wait at least one or two years, until the tree has recovered from transplant shock. Then fertilize only at correct known deficiencies.

Recreate nature's litter by applying a layer of composted wood chips two to four inches thick over the entire area you rototilled or loosened with a shovel. Avoid placing wood chips directly in contact with the trunk. Mulch will keep the soil cool and moist, return important elements to the soil, encourage beneficial fungi and keep lawn mowers away from the tree.

Staking or guying new trees may be necessary if you're planting in a very windy spot or are planting bare root stock, but it's best to avoid staking if possible. If you must stake, use wide bands of nylon strap or carpet to support the trunk and make sure the tree has room to move a little. Wire, even surrounded by a garden hose, can causes serious damage to the trunk and should not be used. Don't pound the stakes through the root ball, and remove all staking hardware within one year after planting. Studies have found that tree wrap can do more harm than good, and should not be used.

A young tree needs all the energy it can get, so don't do much pruning at planting time. The leaves on the branches will help the tree produce the energy it needs to get established in its new location. Broken or dead branches and double leaders should be removed right away, however. Otherwise, it is best to wait two or three years for the first pruning.

Water is key to the survival of your newly planted tree. Young trees should be watered as needed throughout the season, about one inch per week. To avoid over-watering be sure to check soil moisture under the mulch and adapt watering to rainfall and soil conditions.