How Deep to Plant a Tree for Healthy Growth

The Best Time to Plant a Tree

Trees (and shrubs) can be planted any time of the year that you can dig the proper planting hole. However, there are better times than others for multiple reasons.

Suffice it to say, the more time you can put between when you plant a tree, and the arrival of summer, the better. That makes fall the very best time of year to relocate trees and shrubs or plant new ones. Early spring is a popular time as well.

How to plant a tree the right way – follow these seven important steps:

-1. Prepare the proper planting hole. When preparing any hole for planting, make it three times wider than the current root mass but never deeper than the plant was growing in its previous environment.

An even better guide with trees is to look for the flare of the trunk near the soil level. Don’t place the tree in the planting hole so deep that any part of that flare is covered with soil. The truth is, even nurseries sometimes put plants in containers too deeply. There have been many times where I’ve actually had to pull away soil to find the base of the trunk flare and true surface roots. Make a habit of checking this.

-2. Plant high. I go even one step further by placing trees and shrubs in their new environment with up to 25% of the root ball higher than the surrounding soil level. I then taper soil up to cover all the roots and add a generous layer of mulch above that. Newly disturbed soil tends to settle and shrubs and trees planted at grade can quickly settle below grade and succumb to root rot or disease.

In my book, it’s always better to plant a tree or shrub slightly high and allow the area to drain away rather than for a plant to sit in a bowl and collect excess water.

-3. Inspect the roots and disturb when necessary. Once the plant is out of its container, look at the roots. If they are densely bound in a circular pattern or have started growing in the shape of the container (even slightly), break up the pattern.

It’s vitally important to stop this pattern now. The biggest mistake you can make at this point is to place a rootbound plant into the ground as is. Unless you break up the pattern, you’ve likely sentenced the plant to a slow death. At a minimum, it will likely never establish or reach a fraction of its potential.

Don’t worry about hurting the roots or losing soil as you break the roots apart or even cut some away. Better to give them a fresh start than allow the constrictive pattern to only get worse below ground. While you don’t want to be any rougher than necessary, do what you must to arrest the pattern.

I often scratch my fingers across the sides and bottom of the root mass in mild cases. In more severe situations, I’ll slice up the roots vertically with a pruning saw, hack off the bottom inch or so, and or pull apart the root mass to clearly create new opportunities for non-circular new root development.

-4. Don’t amend the soil. Contrary to traditional planting methods, contemporary research indicates that you should not amend the hole with additional organic material (unless you intend to amend the entire area where roots will eventually grow). Roots growing in amended soil rarely venture into harder native soil. The long-term affect is a smaller root system, reduced growth and a less hardy plant.

Instead, simply break up the clumps in existing soil, remove the rocks and backfill. Studies show plant roots growing in only the native soil actually did a better job at establishing and expanding beyond the original hole.

-5. Eliminate air pockets. While you could lightly tamp or hand-pack the soil around the plant roots to ensure good soil-to-root contact, I prefer to add a stiff spray of water to the hole after backfilling half way. Not only does it provide needed moisture but the water also helps eliminate air pockets that could otherwise result in dead roots or worse (without compacting the soil too much). Finally, water again gently but thoroughly once all the soil is in place.

-6. Add mulch. Starting about two inches from the trunk (leave this area exposed), place roughly two inches of organic matter such as shredded leaves, or ground bark or nuggets around the plant, at least out to the drip line. Further is better. Mulch helps retain much-needed moisture and helps keep roots cooler near the surface—a very important requirement for newly installed plants.

-7. Water Properly Until Established. The most important job you will have after planting is to keep plants and trees well watered until established. This can take weeks to months, to even a year or more in some cases. But don’t worry. You can put this part of the process on auto-pilot. (I’ll tell you how below.)

The key to proper watering and establishment is slow and deep irrigation. It’s not practical to do that by hand. The only way to establish trees properly through irrigation is with soaker hoses or drip irrigation.

The slow and deep irrigation allows the soil around the roots to saturate, so the roots have time to absorb the moisture, while avoiding excess runoff. Short, manual blasts of water from an overhead hose or sprinkler system simply don’t come close to providing the same effectiveness for water delivery.

I water newly planted trees every day for about the first week. For the next two weeks, I ease off to about every other day. Then gradually ease back from there.

However, there’s a fine line between watering enough and watering too much—especially with large trees that arrive with root balls wrapped in burlap. These trees have lost all their feeder roots when dug from the ground. Providing adequate water is critical to their survival and establishment.

That said, I’ve killed more than one tree like this by overwatering. Even if you prepare a large planting hole, when drainage is poor, the root ball may be sitting in water and literally drown. There’s no easy way to know how wet the soil is deeper into the planting hole.

The best advice I can offer is to pay close attention to how the tree responds (and all your plants for that matter). While it’s common for them to lose up to half their leaves to transplant stress (a normal part of the process), more can indicate a potential problem.

If you sense the tree is responding poorly, and you are watering consistently, you’re likely over-watering. If the leaves are turning brown, drying up, and falling off, and the soil appears dry, water more.

To add to the challenge, soil that appears dry at the top may be very wet a few inches down. And the opposite is true as well. All the more reason it is important to apply your detective skills based on observation and knowing how much or little you’ve been watering.

In the first few weeks, soil that is moist but not soggy is your target range. And depending on what you’re using to deliver the water will affect how long you need irrigate per session. So there’s no simple answer.

Proper Tree Planting Depth | From the Ground Up

FAQ

How deep should you dig to plant a tree?

A good rule of thumb is that a tree’s root system should be planted at about the same depth as it grew in the nursery.

Can you plant a tree too deep?

• Why Planting Too Deep is Harmful:

  • Bark Decay: When the base of the trunk is buried, it can lead to excessive moisture and rot, which can compromise the tree’s ability to transport nutrients and water. 

  • Reduced Oxygen: Deep planting can suffocate the roots, preventing them from getting the oxygen they need to grow and function properly. 

  • Girdling Roots: Roots that are buried too deeply may start to grow upwards, potentially forming a ring around the trunk and restricting its growth. 

  • Increased Susceptibility to Pests and Diseases: A stressed tree is more vulnerable to pests and diseases. 

  • Stunted Growth: Deep planting can lead to slower growth, smaller leaves, and reduced overall vigor. 

  • Death: In severe cases, planting a tree too deep can lead to the tree’s death. 

• How to Identify a Tree Planted Too Deep:

  • Check the Root Flare: Look for the point where the roots transition to the trunk. It should be at or slightly above the soil surface. 

  • Observe the Trunk: If the trunk appears to be going straight into the ground, it’s a sign that the tree might be planted too deep. 

  • Look for Signs of Decay: Check for any signs of bark decay or rotting at the base of the trunk. 

  • Note the Soil Level: If there is a significant amount of soil mounded around the base of the tree, it’s a good indication that the tree is planted too deep. 

• How to Fix a Tree Planted Too Deep:

  • Dig Away Excess Soil: Carefully remove the soil around the base of the tree until the root flare is exposed. 

  • Re-evaluate the Planting Depth: If the root flare is significantly below the soil surface, it may be necessary to replant the tree at the correct depth. 

  • Ensure Proper Drainage: Make sure the soil around the tree is well-drained to prevent excess moisture from causing rot. 

  • Avoid Mulching Too High: Mulch can help retain moisture, but it should not be piled up against the trunk, as this can also lead to problems. 

  • Consult with an Arborist: If you are unsure about how to fix the problem, it’s always best to consult with a professional arborist. 

What is the 10/20/30 rule for tree planting?

• Purpose:

  The rule aims to reduce the risk of catastrophic tree loss due to pests, diseases, or other threats that can disproportionately affect certain species, genera, or families. 

• The Numbers:

  • 10% (Species): No more than 10% of the urban tree population should be of the same species. 

  • 20% (Genus): No more than 20% of the urban tree population should belong to the same genus. 

  • 30% (Family): No more than 30% of the urban tree population should belong to the same family. 

• Example:

  If you’re planting trees in a city, you wouldn’t want to plant 50% of the trees as the same species (e.g., all American elm), 40% of the trees as the same genus (e.g., all Quercus or oak), or 70% of the trees as the same family (e.g., all Fagaceae or beech family). 

• Rationale:

  By promoting diversity, the 10/20/30 rule helps to create a more resilient urban forest that can withstand various threats. 

• Implementation:

  • The rule can be applied at different scales, from a small neighborhood to an entire city. 

  • Urban foresters and designers need to work together to incorporate diversity guidelines within established design principles. 

  • Some have proposed corollaries to 10-20-30 such as the “Look around rule.” This guide states if you’re getting ready to plant a tree; look around and if you already see that tree, plant something else. 

• Criticisms:

  Some argue that the rule is not restrictive enough and that even a small percentage of a vulnerable species or genus can still lead to significant losses. 

• Alternatives:

  Some propose narrowing the limits, such as no more than 5% of any one genus. 

What is the minimum soil depth for planting trees?

Soil Depth

Tree soil should have a minimum depth of 3 feet (1 m). The soil can be composed of topsoil and subsoil layers. When installing the soil it should be installed in lifts or layers of < 12 inches (30 cm).

How deep should a tree be planted?

Trees should be planted with the base of the plant at or slightly above soil level to avoid planting them too deeply. The hole should be at least three times the width of the root ball for potted trees. For bare-root trees, dig the hole at least twice as wide as the extended root system.

Did you plant your new tree too deep?

In your planting bliss, make sure you didn’t make the most common tree planting mistake – one that could keep your tree from reaching its full potential. Check that you didn’t plant your tree too deep. Below, we’ll help you determine if you did indeed plant your new tree too deeply and how to fix the problem.

How do you know if a tree has been planted too deep?

One simple check can indicate if an existing tree has been planted too deep. When viewing the lower trunk, it goes into the ground like a fence post goes into a hole. There is virtually no change in diameter where the trunk and soil meet.