Planting a tree is an investment in a future with more beauty and shade, less air pollution and flooding, and many other good things that a healthy canopy of trees brings to us and our communities.
But that’s only if you choose the right tree and plant it the right way in the right place. “Get the first steps right and you will greatly improve your chances of enjoying that tree for many years to come,” said Sharon Yiesla, plant knowledge specialist at The Morton Arboretum in Lisle. “Do it the wrong way and you are setting the tree and yourself up for trouble.”
As we celebrate Arbor Day on the last Friday in April, here are some tips for choosing and planting trees.
Suit the tree to the site: Make sure the species or variety is a good match for the sunlight conditions, soil and available space. Remember that trees grow wider as they grow taller. Read the plant label. Get more information from the Arboretum’s website at mortonarb.org/plant-protect.
Don’t plant too deep: “This is a very common mistake that leads to a lot of problems,” Yiesla said. If roots are buried too deeply, they can be smothered. If the lower part of the tree’s bark is covered in soil, it can rot. To avoid this big mistake, figure out in advance exactly how deep the hole should be, and be careful not to dig any deeper.
Locate the root flare: To determine the hole depth, find the place where the tree trunk widens out into its roots, the way your neck widens out into your shoulder. That’s called the root flare. Be aware that the root flare may be buried in soil or mulch several inches deep when you buy the plant. Dig down to find the flare out into the first big roots and remove all soil above that point. “When you plant the tree, the curve of the root flare should sit at the level of the surrounding soil and absolutely no deeper,” Yiesla said.
Measure the root ball: Whether the tree came in a pot or tied up in burlap, you will need to know the width and depth of its ball of roots to dig a hole that is the right size. Measure from the root flare down to the bottom of the root ball, and then measure the width of the root ball.
Dig a wide, shallow hole: The hole should be at least twice as wide as the root ball, or wider if possible. It should be only as deep as the root ball. The hole should have sloping sides to encourage roots to grow out wide into the surrounding soil.
Position the tree: If it came in a container, slide the pot off. If it came in a fabric grow bag, cut it off. If it is wrapped in burlap and possibly a wire basket, wait to remove the burlap until the tree is in the hole. Lift the tree by the bottom of the root ball, not by grabbing the trunk, and set it in the hole. Try to keep the root ball together as you lift it.
Inspect the roots: Look for roots that are growing around in a circle on the surface of the root ball. To encourage them to grow out into the soil instead of continuing to circle, either pull them free with your fingers or cut them with sharp pruners.
Remove burlap: If the tree was wrapped in burlap and wire, cut away as much as you can reach after you have set it in the hole.
Double-check: Make sure the root flare is at or just slightly above the level of the surrounding soil. If necessary, tuck a little soil under the root ball to lift it up to the right level. Walk all around the plant to check that it is centered and straight, judging by the lowest 2 or 3 feet of a tree’s trunk.
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 with at least 10 gallons of water, allowing the water to gently soak into the root ball. Spread an even layer of mulch about 3 to 4 inches deep over the root ball and in an area around it at least 3 feet wide. Do not pile mulch against the tree’s trunk; that can cause the bark to rot. Keep the mulch 3 inches away from the bark. Continue watering regularly for at least two years.
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.
