1 of 4
Ready to plant
This container-grown Japanese maple tree is ready for planting. Remove the tree from its container and inspect the rootball to prepare for planting.
Photo by S. Cory Tanner
2 of 4
Find the topmost root
Clear excess soil from the top of the rootball so you can locate the topmost root, which will help you determine how deep to dig your planting hole and check your final planting depth once the tree is placed in the hole.
Photo by S. Cory Tanner
3 of 4
Remove circling roots
Inspect the rootball for any defects, such as circling roots, which should be removed, so roots can grow freely out from the tree.
Photo by S. Cory Tanner
4 of 4
Check the depth
Measure the depth of the planting hole to ensure that it is no deeper than the depth of the topmost root. You can use a shovel handle laid across the hole to check the depth. The topmost root should be one or two inches above the final soil grade to allow for settling and prevent the root flare from getting buried. After the tree is planted and mulched, the topmost root should still be visible.
Photo by S. Cory Tanner
Returning to Clemson University to pursue a doctorate exactly 20 years after I first stepped onto campus as an undergraduate, I’m reminded of a favorite saying: “The best time to plant a tree is 20 years ago; the second-best time is now.” Today, I meander through mature, shade-bearing oaks I remember as small trees, because someone planted them during my first tenure.
Properly planted trees grow faster than most people realize. Given a good start, most should outlive their planter. Unfortunately, many don’t make it to their 20th birthday. One primary reason young trees die is improper planting. And the biggest planting mistake? Planting too deep!
Planting depth is critical to a tree’s long-term survival. Unfortunately, it’s not as simple as just planting to the depth of the container or rootball. Here are simple steps to giving a young tree a strong start.
Find the topmost root. Before you start digging a hole, figure out the proper planting depth by removing your new tree from its container and looking for its topmost root arising from the stem or trunk. You may need to clear some soil from the top of the rootball to find that top root. That’s the landmark for what will become the tree’s root flare. This swollen base must be above ground. Tree trunks that go straight into the ground like a telephone pole, with no flare, were probably planted too deeply and will likely grow poorly or die.
Prepare the rootball. While searching for the topmost root, examine the rootball for defects. The most common problem is circling roots. Without obstruction, roots will grow in nearly straight lines away from the stem of a tree. However, circling roots are nearly unavoidable in plants grown in containers. Roots follow the inner surface of the container, searching for nutrients, water and escape from confinement. They won’t magically straighten themselves after planting, so they must be removed before planting. If not, they grow as the tree grows, eventually becoming girdling roots that will strangle a tree to death.
Dig the hole. After preparing the rootball, measure its height from the topmost root to the bottom. Subtract an inch or two; that’s the depth to dig your hole. No deeper! This measurement accounts for settling and will position your tree’s topmost root at or slightly above the soil grade. Roots rarely grow deeper than the top six inches or so of soil, so digging further down will only result in too-deep planting. Leave the bottom of the hole firm. You can dig the hole as wide as you want. Two to five times the diameter of the rootball is standard; wider is better.
Backfill. With your tree in the hole, use a small amount of backfill soil to stabilize the tree and make sure it is vertical. Use a straight edge (a shovel or rake handle will do the trick) across the hole to check the height of the topmost root one more time. It should fall in line or slightly above the line. Once satisfied with the planting depth, backfill around the rootball with native backfill soil (the soil dug from the hole). No need to add compost, fertilizer or other special ingredients. At best, they’ll be wasted in the bottom of the hole, because roots won’t grow there anyway. At worst, they’ll interrupt water drainage, resulting in a hole that either holds too much water or dries out too fast.
Water it in. Water the newly planted tree well to settle soil around its roots. A good flooding helps eliminate air pockets. A good rule of thumb is to flood the rootball once a week for the first year in absence of rainfall. Gradually reduce waterings until it is not watered at all, except during severe droughts.
Mulch properly. A two- to three-inch layer of mulch over the planting hole’s surface preserves moisture, prevents weeds and promotes the tree’s survival. But covering the tree’s lower stem with mulch has the same effect as deep planting, so keep mulch six inches away from the plant stem.
South Carolina Arbor Day is the first Friday in December—a good day to plant a tree. Plant it properly, so you and others can enjoy the shade for a lifetime.
S. CORY TANNER is an area horticulture agent for Clemson Extension based in Greenville County. Contact him at shannt@clemson.edu.