When one plants a tree, they enter one of the more epic long-term relationships. Depending on the species, there’s a decent chance the tree will be one the original planter’s grandchildren, and even great grandchildren will enjoy. Making the right choice is critical.
Doris Taylor, horticulturist and Plant Clinic manager for The Morton Arboretum in Chicago, offers some tips for picking the right tree and giving it the best possible start.
- Assess limiting factors
Each tree thrives, or struggles, in specific environments. If the site is already determined, consider the factors that will impact the tree. How much sun does the site receive, what is the soil condition, in what hardiness zone will the tree be located, and what size will the tree be at maturity?
“Sun loving plants, such as the magnolia, may survive shady conditions, but they will produce fewer flowers and have a spindly look. It’s best to plant trees in the conditions they prefer to achieve the best result,” Taylor says. The same is true for soil moisture. “Some trees tolerate temporary flooding, such as elms, river birch, and Freeman maples, and might be better bets near a downspout or low spot where water occasionally collects.”
The space will also determine the tree’s size. Taylor warns to watch for overhead wires. They usually hang at a height of 25 to 30 feet. Select trees that don’t exceed the 20 to 25-foot ceiling at maturity. Larger trees will likely be treated to an asymmetrical trim job courtesy of the power company. Planting a more moderately sized tree will help avoid that situation. Knowing the ultimate size of the tree is also important when planting near the home.
“A tree that will reach 40-feet tall and 20-feet wide at maturity will need to be planted at least 10 feet from the house so neither branches or roots will grow into the house,” Taylor says. She notes while tree roots will not break through foundations or pipes on their own, they’re opportunists and will work their way into cracks. Roots will generally grow two to three times the width of the tree. Leave space for them to spread free of pipes and foundations if possible.
- Determine Wants
Once all the limiting factors are identified, a tree shopper can move on to wants, such as size, shape, leaf type, showy blossoms, fall leaf color, and more.
A common want is for a tree that grows quickly. “Keep in mind the trees that grow fast can be a bit weak wooded,” Taylor warns. “Ornamental pears have beautiful white flowers, great color in fall and grow quickly, making them popular. But they have weak branch attachments that start to snap off after about 20 years. We don’t recommend them.”
The Morton Arboretum web site offers a tree selection tool to help those in their region wade through their limiting factors and wants, providing a narrowed down list of species that suit their needs. Similar tools and recommendations can be found for other regions on local arboretum or university extension web sites.
- Be Different
When it comes down to the final selection, aim for diversity in tree species both in your own yard and in relation to the neighborhood, Taylor says. “A lot of people in our region are replacing ash trees because the emerald ash borers and the weather patterns have caused the ash trees to decline and die,” she says. Ash trees abound in her area because when Dutch elm disease came around, everyone replaced their dead elm trees with ash. “Now that the ashes are dying, everyone’s looking at maples. I see the future repeating itself.”
- Purchase and Plant
With species dialed in, it’s time to purchase. Taylor recommends balled and burlapped trees first, potted trees second, and encourages people to be cautious of bare root trees. Bare root trees can be fine, she says, but special care should be taken that they are not planted too deep.
“With ball and burlap you can get into the larger 8 to 12-foot trees,” she says. But it may not be best to pick the largest tree on the nursery lot. “For every 1 inch of diameter it will take 1 year for the tree to reestablish the roots it lost from being transplanted.” That means a larger tree may spend multiple years rebuilding roots before doing much growing, while a smaller tree will rebound faster and possibly end up larger, sooner.
Spring and fall are the best times to plant trees, but Taylor warns not to plant into wet soil. Wait until soils are dry and mellow, but not too hard.
“Everyone wants to hurry up and get out in the spring, but watch the long-term forecast,” she says. “We don’t want to get too cold, we want nice warm soils for planting in.” In northern climates, she recommends fall planting no less than 6 to 8 weeks prior to winter so the tree has time to acclimate.
For planting, Taylor says the hole should be dug deep enough so that the top of the soil level in the pot or burlap is at ground level. For best results, loosen the soil about 2 to 3 times the width of the hole around the tree. “The roots have an easier time establishing in looser soil,” Taylor explains. Once the tree is in the hole, remove any wire basket and burlap and twine if possible. At the very least, use a knife to remove the top layer of burlap, if exposed it will wick moisture away from the root ball.
Water thoroughly after backfilling the hole to settle the soil. Depending on location and the size of the tree, newly planted trees need 10 to 15 gallons of water per week. Putting down 3 to 4 inches of organic mulch, such as wood chips, in a 3-foot diameter around a newly planted tree can help conserve moisture and prevent weeds. Keep the mulch several inches from the trees trunk.
“You don’t want the mulch to touch the trunk. We don’t want it to look like a volcano around the tree, more like a donut,” Taylor says.
Once it’s in the ground, leave the tree be other than watering. Taylor says fertilizing and pruning (unless there are damaged or diseased branches) can wait until the roots get established.