Do you have a tree that seems to stick straight out of the ground like a telephone pole? If you can’t see the root flare, you have a tree planted too deep!

Why is this a problem? 

1. Bark rot. Tree bark will rot if buried under damp soil. Not good for the tree.
2. Suffocated roots. Tree roots generally grow horizontally and close to the soil surface so they can ‘breathe’. Buried tree roots will struggle to ‘find’ the soil surface and may never do so, resulting in eventual decline and early death (harsh).

How does a tree get planted too deep?

Trees often get planted too low by inexperienced gardeners. We have a few trees planted too deep – by me! My young and eager self didn’t know what I was doing. I had good intentions but poor execution. I sank the rootball lower in the ground to create a berm around the planting hole that would hold water. How dumb that sounds as I write it now. The berm held water as intended, but I should have set the tree base at ground level and built up a berm around that. Duh. 

Additionally, the Hinoki Cypress tree in these photos suffered a second assault. Not only did I bury it too deeply from the outset, but it became buried even further when we hired landscapers to install a retaining wall. I planted this beautiful conifer on a slope, and now the slope was raised and leveled out, submerging the trunk area even more. There was no way around this other than to lift a rather mature tree out of the ground – not really possible without hiring pros to do it (read: expensive!). I probably should have added that item to the retaining wall project. Oops.

How did I save these sad, sunken trees?

Despite my repeated attempts to scoop material away from the tree trunks, it would inevitably build back up over time and wind and weather. I decided I needed a permanent solution, so last year I built a mini retaining wall on the high side of the slopes. 

I started with the Hinoki Cypress. I dug out the uphill side about 1.5 feet from the trunk, low enough for the new soil base to be roughly level with the tree root flare. Then I dug out the area horizontally. Once I had a flattish soil base, I stacked 2 rows of bricks in a woven pattern on the uphill side. The resulting wall is arranged in a slight arc shape for stability.

Did I explain that clearly? Probably not; here are some handy illustrations!

I used standard red brick for the ‘wall.’ Our house is very old, and over time, I’ve amassed quite a collection of old bricks that I’ve dug up while gardening, so I had those on hand. (Why are there so many bricks in the ground? I’d love to know – they seem evenly scattered around our property.). But you could use stone, logs, or some prefab border material like interlocking bricks.

My second specimen is this vine maple, which I planted on a slight slope of very soft soil behind our garage. Not only did I plant it too deeply to begin with, but it also sank after I planted it! Luckily, vine maples are native understory trees that can take some buildup of organic debris which it typically encounters in their natural environment. But this cultivar is grafted, and the graft union makes it extra vulnerable, so I had to fix this tree too.

Success! And a caveat.

So far, these two trees are thriving, the Hinoki Cypress having been in the ground for 6 years and the Vine Maple for 5. Note that this excavation will help keep mulch and soil away from the trunk and prevent rot; however, your tree may still struggle with root suffocation depending on how deeply it’s buried and how long it’s been in the landscape that way. 

This retaining wall method is an inexpensive solution for smaller trees that have been in the ground too long to move. Will they eventually succumb to root suffocation? Perhaps, but I’m very optimistic. 

Alternative solutions for saving a tree planted too low

Depending on your situation, there are a couple more surefire ways to tackle the issue.

1. Dig up and raise it. If the tree is small enough for you to handle and/or has been in the ground for less than a year, simply dig it up, add some soil to the bottom of the hole, and replant it so that the root flare is level with the ground. This method sets the tree back a year in terms of getting established but is best in the long run. (I successfully used this method for a Paperbark Maple and Tricolor Beech, 2 other victims of my novice gardening practices).
2. Replace it. Admittedly this is not saving the tree, but it will save you the heartache of watching a tree die. Replacement is the best solution if the tree is already in decline or you want to make a garden edit anyway. Get the doomed tree out of there and start fresh. Clearly, this is not the cheapest option, but if your tree is dying, it’s better to rip off the bandaid and get a new tree planted and established. Future you, who is enjoying a nicely maturing new tree, will thank present you. 

Tips for planting trees at the right depth

And the very best solution is to do it right in the first place! It might seem obvious: just plant the tree so the root flare is level with the soil’s surface. However, there are some gotchas to look out for:

1. Sometimes nurseries sell trees already planted too deeply. You would think nurseries would get it right, but it happens. When plants are up-potted – say from a plug to a 1-gallon – nursery workers may add too much soil to the top of the pot. This can happen several times as the tree grows and is moved to larger and larger containers. In fact, I recently purchased a not-inexpensive, mature Japanese maple buried 2 inches too deep in its 10-gallon container. To rescue trees like this, check the root ball to find the root flare and remove the soil until it’s level.
2. Trees can sink after planting. How much depends on your soil and the nursery’s growing media. If it can compact, over time, it will. If you dig the planting hole too deeply and need to backfill it with soil to get the root ball up to the correct height, make sure to compact the backfilled soil a bit to create a solid base. 
3. Mulch can become the new ground depth. I mean that by piling mulch too deeply around the tree, you create the same conditions as a tree that is planted too deeply in the first place. If too much mulch is added over several years, that mulch breaks down and forms a solid mat of soil-like material that can rot the tree trunk and bury roots. When mulching, mulch lightly around the tree and keep all mulch several inches away from the tree trunk.

I hope these tips help you avoid my mistakes as a beginning gardener. And if you’ve already made them (like I did), I hope the retaining wall solution and other ideas for saving an over-planted tree work for you. 

What do you think of this retaining wall idea? Did you try it, and did it work for you? Let me know in the comments!