Fall is approaching and it's almost prime tree-planting season! While you can plant a tree at almost any time of the year, the fall is a great time with cooling days and nights, more rainfall, and the tree already slowing its above-ground growth in anticipation for winter.
But it’s vital to know the right way to do it for success!
Watering, soil, timing, location, and pruning are all factors to remember! But proper planting depth is a major key to a successful transplant.
The Proper Depth For Planting a Tree
The right depth is vital to a long-term, stress-free healthy tree!
Roughly 80% of a tree's root system is located in the upper 18-24 inches of the soil surface, and extending out for many feet away from the trunk. Roots like to grow in the warmer soils closer to the surface where they can grow out in all directions to find food and water while stabilizing the above-ground portion of the tree.
Planting new trees are most often are planted too deep. Planting too deep results in those feeder roots smothering due to lack of oxygen which can lead to deterioration of the bark at the soil line and also kill the tree.
But planting too shallow does occur leaving the surface roots to become exposed (often when the soil has washed away, or the root ball wasn’t planted deep enough), you’ll end up having your tree's main support system dry out, be eaten by rodens and insects, and be exposed to the hot sun and chill in the winter.
Despite sometimes adapting to a slightly deep or slightly shallow depth in the ground, you will drastically shorten your tree's life expectancy!
Improper Tree & Shrub Planting Depth Can Lead To
- Stress (Increased susceptibility to insect or disease attack)
- Reduced root growth (from lack of oxygen)
- Exposed roots
- Root girdling
- Bark splitting
- Cankers
- Disease and decay
- Root rot
- Insect infestation
- Failure to establish
Trees with tap roots may survive being planted too deeply, but they will be drastically compromised and their buried bark will suffer. Most trees have roots that fan out and anchor the tree but feeder roots need healthy soil that is well-drained and has oxygen and easy-to-access moisture.
Some trees even can sprout roots where the soil is touching them, causing problems later on. Especially with grafted trees.
Even just a few inches off and it can spell doom!
How to Ensure Proper Planting Depth
Once you have selected a plant for your hardiness zone, and one that meets your sun requirements and location, then it's time to dig the hole for your new plant.
- First, contact your local Digger’s Hotline to make sure your site is safe for digging.
- Prep your root system by soaking the roots per directions that come with your plant.
- Once you are ready to start digging your hole, you’ll want to have a rough idea of how big your tree’s root ball is. It’s helpful to have the tree and its container, or the bareroot available to know of their size. This way you will know how deep to dig. However, if you’re getting a head start on the labor, you might find yourself digging before the tree is there for measurements. In these cases, we suggest digging a shallow, wide hole based on the expected container size. You can then always adjust when the tree arrives. (Just cover the hole until you can plant in it, or else you may have some twisted ankles!)
- The hole should only be as deep as the root ball is, and no deeper. There is no need to loosen the soil at the bottom of the hole - this way your tree will not sink as the plant settles into the hole. But dig twice as wide as needed. (If you’re digging 12 inches down, you’ll want to dig your hole two feet wide in diameter.)
- Fill the hole with water to prime the soil and hydrate it. Let that water drain away before setting your root ball into the site. Don’t forget to sprinkle Nature Hills Root Booster at the bottom of your planting hole for an extra life-long boost.
- Once you’ve removed your tree from its plastic container (you may need to gently cut it away if roots are growing through the drainage holes), you’ll want to gently tease its roots apart and destroy any roots growing in a circle at the bottom of the root ball.
- Arrange the roots out and spread them gently so they’re not all growing in one direction.
- While situating the roots, keep an eye on the top soil layer and surface roots of the tree. They should sit no lower or higher than where it is initially planted in their container, or where bareroot was previously in the ground. The soil level of container plants should match and bareroot plants should be even with their former soil level.
- Once you’ve got your tree placed, go ahead and backfill with the same soil excavated to dig the hole, and gently pat down well. Ensure the soil is not mounded and sloping away from the stem so that soil and water wash away.
- Water in your new tree and watch the soil level closely as it settles. Add more soil if it settles and exposes the roots or washes away. (You can create a ring around the planting site to hold water and soil in.) The water will help to get rid of any remaining air pockets.
- Most trees arrive with a sturdy stake, but some trees need to be staked to keep them growing straight until new roots can develop - especially those in windy, exposed areas. The stake should be taken off after the first growing season in its new home.
A properly planted tree will have its trunk free and clear and show a slight flare (root flare). If your tree trunk goes straight into the ground, it may be planted too deep. Carefully remove the topsoil at the trunk and find the place where the root flare is and use that at the proper planting height.
Planting Depth and Bareroot Trees
For bareroot trees - you’ll see a change in color or texture between the above-ground bark layer and the below-ground portion. And you may still see some soil at the transition. Also, look for the root flare. If you are working with bareroot plants be sure to plant all roots just under the soil surface and not bury them too deeply. Many times, the planting depth is visible on a bare root plant showing where they were grown at the nursery. Plant by fanning the roots out over a mound at the bottom of the hole and backfill until the level is correct. Then fill with moist soil and gently, but firmly pack it down.
Planting Depth For Grafted Trees
Many trees are grafted onto special rootstocks that help them withstand pests, diseases, and temperatures, and control their size among other perks. The graft on a new tree will often be just a few inches above where the soil level is. Planting too deep and even covering this graft (often looking like a slight dogleg or angle) with soil will smother the roots and kill the tree and its scion.
Why Mulch Is Important
Another kiss of death besides planting too deep or shallow is the addition of mulch up against the trunk of the trees and shrubs. Known as "Mulch Volcanos", having too much mulch will have the same effects as having too much soil. Mulch is great over the roots of plants, but not against the stems of the plants above ground.
Adding a 3-4 inch layer of arborist bark chips over the soil surface right after planting helps maintain soil moisture more regularly, keeps the surface roots cool, and insulates them from the winter chill. The mulch breaks down and enriches the soil.
Do not cover the crowns of ornamental grasses, perennials, or Roses, or fill the interiors of shrubs with mulch and soil either. You will create just as many problems as you are trying to solve.
Happy Roots Mean Happy Trees!
Proper planting and planting depth are paramount to having a lasting leafy legacy in your yard! And Nature Hills is here to help you every step of the way!
Get ready for the fall planting season now and you and your landscape will reap the rewards for years to come!
Happy Planting!
