PBS Utah Modern Gardener

How to Properly Plant a Tree

By Ashley Swansong and Christina Van Otterloo of PBS Utah’s Modern Gardener

Looking to spruce up your outdoor experience? Ignore decor and turn to the trees. Trees do wonders for your outdoors; quieting environmental noises, cooling off your property, filtering the air, and providing habitat for birds and other wildlife. But planting a tree takes some planning and preparation especially when planting it correctly.

We met with master arborist Will Pruitt, of TreeMendous Arbor Care, to learn how to correctly plant a tree so it will grow and thrive for years to come. “I’d say 9 out of 10 trees I see are planted incorrectly,” said Pruitt, whose specialty is tree diagnostics, but whose passion is tree planting.

Pruitt has seen too many improperly planted trees across Utah, which he says will ultimately result in the tree dying sooner than later. But with a little guidance, he says anyone can have a healthy, long-lasting tree. This step-by-step guide will show you just how to correctly plant a tree.

Cynthia Stringham (L) of Modern Gardener and Will Pruitt of TreeMendous Arbor Care with a newly planted tree.

Before You Plant

A few things to consider before planting a tree: season, type of tree, and location.

In Utah, it’s best to plant in the spring or fall, when the ground is thawing and it isn’t too cold.

And when choosing your tree and its location, consider factors like the tree’s estimated size, the amount of shade it will provide, and whether its growth could cause any structural damage. 811 is the national “call-before-you-dig” number to call to make sure you won't be hitting any utility lines.

Once you have those settled, it’ s time to prep.

Start by Exposing the Root Flare

Contrary to popular practice, “don’t start by digging the hole!” says Pruitt. The first thing you’ll need to do is expose the tree’s root flare and measure the root ball to learn just how big your hole needs to be. The size of the hole is crucial to the tree's development and it’ s usually a lot smaller than the container the tree came in.

The root flare is the basal area of the tree where it begins to flare out below the trunk, just above the main branching roots. It’s usually buried about 6-8 inches below the surface of the soil your tree came in. This excess soil is added at the nursery, especially if they had to replant the tree in a larger pot.

Pruitt describes root flare as the heart of the tree, pumping water up and down the arbor and providing it with oxygen.

To expose the root flare, remove the tree from the container and cut off the excess soil at the top using a tool like a sod knife.

Final treated root ball with root flare exposed, girdling roots severed, and root ball loosened.

Sever Girdling Roots and Loosen Root Ball

While you’re exposing the root flare, you’re likely to come across girdling roots. They’re often only the diameter of a grain of rice! Using snips, sever any girdling roots. If left, they could grow around the base of the tree's trunk or around its main roots and essentially strangle the tree.

Once the flare is exposed, make two to three incisions down the sides of the root ball to sever the roots encircling it. This directs the roots to grow out in search of water, which will establish a strong foundation.

Finally, tip the tree to massage and loosen the bottom of the root ball.

Measure the Root Ball

Before digging the hole, start by measuring the width of the root ball from across the top. Your hole needs to be twice the diameter of your root ball. In our case, the diameter of our root ball was 10 inches, so our hole’s diameter was 20 inches wide. Considerably smaller than the container the tree came in!

The depth of your root ball is important. You don’t want your hole to be too deep. Pruitt stresses that your tree should be sitting on undisturbed soil. That way your tree isn’t sitting in a “bowl of water” which can cause root rot. Your root flare should sit 1 inch above your finished grade, or the final surface area of your planted tree.

Will Pruitt and Cynthia Stringham measuring the treated root ball to determine the size of the tree's hole.

Measuring the hole and making fine adjustments.

Dig Your Tree’s Hole

Take a shovel and make a circle the size of your hole. Start by removing only half the depth of your hole with the shovel. Carefully set aside the soil you're removing so you can later use it to backfill the hole.

After digging halfway to three quarters down with the shovel, use a hand tool to dig the rest of your hole by hand. Pruitt used a Japanese hand hoe and tiller. By digging the remainder of the hole by hand you're less likely to dig the hole too deep. A tool like a hand rake also prevents glazing; the smooth, hard edge created by the spade of a shovel. Glazing of a hole restricts the growth of roots and the flow of water.

Once your hole is dug, place your tree in the hole, measure and level your tree. You may need to make small adjustments to your hole.

Nourishing Your Tree

Before planting your tree, Pruitt recommends taking a few handfuls of biochar and sprinkling them in the hole. This high-carbon soil amendment helps retain water and nutrients in the soil.

Next, place your tree in the hole and backfill it using the native soil. Pruitt highly recommends using the same soil you dug from your hole. Roots may not establish a strong system in potting soil from a nursery because they’re less likely to start to grow outward in search of nutrients in the native soil. You can alternate backfilling with soil and amending with biochar as you continue to fill your hole.

Ensure roots aren’t encircling the root ball, but try to direct them outward. Halfway through filling the hole, pour 1.5 to 2 gallons of water around the root ball.

Using your hands and upper body weight, gently pack the soil. Pruitt said to not step or stomp on the soil.

If the soil is too compacted it can restrict the roots and slow water seepage.

Once planted, generously add compost and wood chips around your tree, about twice the size of your hole. The wood chips will retain moisture, while the compost will encourage the roots to reach for nutrients.

Watering Your Tree

Depending on the weather and moisture, a newly planted tree should only need 5 to 7 gallons of water every two weeks.

And voilà! Your newly planted tree is ready to grow into a beautiful arbor.

For a step-by-step tree planting demonstration and our complete interview with Will Pruitt, Watch our Modern Gardener episode “How to Properly Plant a Tree” https://www.youtube.com/ watch?v=sg1LWzd1JnQ