How to plant a tree in your yard

October is a fine time to plant a tree or shrub. “The air has cooled off, but the soil is still pretty warm,” said Spencer Campbell, Plant Clinic manager at The Morton Arboretum in Lisle. That means the tree’s roots will have several weeks to grow before the ground freezes.

Most kinds of trees can be planted before the end of October. Evergreens should be planted as early in autumn as possible. A few kinds of trees should wait until spring, such as bald cypress, American hornbeam, ginkgo, larch, magnolia, hemlock, sweet-gum, tulip tree and willow. The Plant Clinic (mortonarb.org/plant-clinic) can help you select the right tree for your yard and the right time to plant it.

If you do plant a tree this fall, plan ahead for next spring’s emergence of periodical cicadas, which lay their eggs in twigs. “Only very young trees are likely to have any problem with cicadas,” Campbell said.

“It doesn’t need to stop you from planting a tree this fall, but be ready to wrap it up with netting for a few weeks next May and June while the cicadas are active.” For more information, see mortonarb.org/cicadas.

Any time you plant a tree or shrub, it’s important to do it the right way. The most common mistake — one that leads to problems years later and is almost impossible to correct — is planting too deeply. Here’s how to properly plant a tree or shrub. For more details, see mortonarb.org/planting-trees.

Allow enough space. Read the label to find out how wide and tall the tree or shrub will grow. Make sure it will fit the available space. Identify the root flare. On a tree, examine the base of the trunk and locate the spot where the trunk flares out into the big, anchoring roots. “You will need to position the tree so that root flare is at or slightly above soil level,” Campbell said. “That will place the roots close enough to the soil surface so they can absorb the air and water they need.” Sometimes the root flare is buried in soil in a pot or a balled-and-burlapped tree, so you may have to dig down a little to find it.

Measure the root ball. To dig a hole of the right depth and width, use a tape measure or yardstick to measure the mass of soil surrounding its roots. The most important measurement is from the root flare down to the bottom of the pot or root ball. This is the maximum depth of your hole. “You may be surprised to discover how shallow your hole needs to be,” Campbell said. “Sometimes it’s less than a foot.”

Dig a wide, shallow hole. The hole should be two or three times as wide as the root ball, with sloping sides. It should be as deep as the root ball but no deeper. “Think of a shape more like a wide soup bowl than a bucket,” Campbell said.

Trim the roots. If the plant came in a container, remove it from the pot. With a sharp knife or pruners, cut any circling roots. You can also shave a thin layer, about an inch, from each side of the root ball. These cuts will encourage new roots to grow out into the soil. Otherwise, try to keep the root ball intact as you place it in the hole.

Remove burlap. If the tree came wrapped in burlap, place it in the hole before you cut away as much of the burlap and wire basket as you can reach.

Get it straight. Walk around the plant to make sure it is centered and upright in the hole. Double-check the depth. Since planting too deeply is such a danger, double-check that the root flare will be at or slightly above the level of the surrounding soil before you refill the hole. “This is a critical step,” Spencer said. “It can prevent years of problems.”

Refill the hole. Use the soil that you removed. When the hole is half full, use your foot to gently tamp down the soil around the root ball. Finish filling the hole and tamp again.

Water and mulch. Water the tree well, allowing the water to gently soak into the root ball. Then spread an even layer of mulch about 3 to 4 inches deep over the root ball and the area around it. “The mulched area should be at least 3 feet wide,” Campbell said. Do not pile mulch against the tree’s trunk; that can cause the bark to rot.

Keep watering. Continue watering, in addition to rainfall, until the soil freezes this fall, and all through the next two or three years of the tree’s life.

For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.