Backfill around existing tree??

Any problems with backfilling about 18" of dirt around a healthy tree? My place is on a slope, and the original contractor tiered everything with railroad ties. Those are going away, being replaced with CMU block and proper drainage, but this area, I'll have to cover the base of the existing tree with dirt. I don't foresee problems, but input is appreciated. Thanks.

At work, landscapers put bark mulch down around the trees year after year. One good company removed the mulch and showed me where strangulation roots grew around the tree. Now, these are smaller trees about 10-12 years old. Adding mulch every year makes room for shallow roots that can grow around the base. I am not saying this will happen, but it does happen. Just my .02

I've read this will kill the tree and have seen it happen following a mud slide. If the tree is worth saving, lay up a well around it's base and backfill to that.

Ehouse

I have always heard not to do this!

In general this is not a good idea.
You typically get crown rot if you do this with soil. With mulch you get roots.
You can backfill but it needs to be something that won't hold water that will rot the crown.

How old is the tree? An older tree will withstand this, as it's root structure is more mature and can tolerate some abuse. Also, if it is a hardy species, such as oak, it is more forgiving. I have a 50+ year old norway spruce that is girdled with a very stout root due to previous owners mowing discharge against the trunk many years ago; the tree is thriving in spite of this.

I had to do the same thing around some trees when I cut in the driveway
was told it was not a good idea they would die, figured I would take my chances
rather than cut them down while healthy
some lived some died
now I only have to remove a few

ive always heard the same thing, but i will say i had the exact some issue... i needed to bring in fill to level my front yard (you can see in this photo the top of that decorative well roof is level with my front yard and at the point of the large tree shown i filled about 2' worth of dirt around it and tryed to left it taper off the backside (so maybe only 17-18" of fill on backside of tree). This had no ill effects on the tree over 14 years later (i guess i got lucky or something?)

Don't do it. It doesn't matter how old it is, or what species. There's risk to more than the roots, as you can get some serious rot/disease in the lower bark that will slowly kill it.

I don't know what idiot came up with the idea of the "mulch volcano" around tree bases, but the idea is slowly destroying a lot of nice trees.

Edit: I may go take a picture of a large oak that someone did this exact thing to in my yard- one side of the base is rotted out and I recently posted here about how to cut it down without damaging my leach field.

usually when raising a grade around deciduous trees they build a retaining wall around the trunk about 6 to 10 feet away from the trunk and when lowering a grade build a retaining wall at the drip line.

White pines don't seem to like more than half their roots exposed or smothered.
Especially older taller ones

It's a crap-shoot. It may live. It may not. Wouldn't be surprised either way.

Well, guess my plans will change for that area. I don't want to chance killing this tree.
What about a thin layer of river rock close to the base, but not in contact with the trunk? I could lower the CMU tier below that and have the finish grade of the new tier at the same level as the base of the trunk?

i think thats a safer way to go for sure (it will allow some air to still get down the trunk base and prevent any water/moisture from building up around the base of the tree/bark. short of building a large retaining wall around the whole damb tree for people and animals to fall into thats a great idea!

When you bury the roots you severely limit the O2 that can reach them and the will die. Trees produce CO2 just like we do. Luckily they produce more O2 than CO2.

Depending on how the burying is done, you could compact the soil around the roots and that doesn't help either.

Matt

Did this 36 yrs ago around a red oak that was about a foot wide. Today, that tree has a wide fat base, you wouldn't know I changed the ground level. Down the road, my Dad burried a clump of young white birch about 3 feet. Two had crown rot, but after a few years, they all came back strong. You would never know they were under so much dirt. in both cases, there is a slope so there is no pooling water. In my back yard, I had a huge hemlock, I sloped some soil near it but at least 5 feet away. In two years, it died.
Maybe you could add a couple inches of soil yearly and see how you do. I will also add that with trees, it may take a couple of years before you know if they are damaged.

I would just build a stone/block wall around it to keep moisture away. Sure everyone has a story about what they did but, in general, the tree will have issues more often than not.