Need help re: grading around trees - xtra soil added

ncrowne

Hi

Bottom line is last Sept/Oct we put in a fence and had the back yard regraded without knowing that this could be a problem for our trees. NOW that I realize I am hoping that it isn't too late to repair the problem.

So, here is the backstory...

We live in Ottawa Ontario and our neighbourhood is on bedrock (slate). Last Fall we had holes dug to put in fenceposts. The machine went down 2 feet of soil before hitting the bedrock and then had to use the drill to break up the slate to go deeper.

We had quite a bit of slate in piles around the perimeter of the yard (what was taken out of the holes). This 'fill' was used to even out the very uneven yard, the majority of it not coming closer than 3 feet to the mature trees in our yard.

We also had a load of topsoil brought in. This WAS distributed all over the yard, UP TO the tree trunks. I'm sure you are all shaking your heads right now, but I honestly didn't realize at the time that this shouldn't have been done this way.

I would have to say that on the majority of the trees about 1 FT of topsoil was added all around and up to the trunk. The yard was extremely uneven and extreme grading needed to be done.

We have on our property in the back one pine tree and about 5 oak trees. They are all pretty mature trees.

I have been reading about the roots needing access to air for gas exchange, venting pipes, my head is spinning. I would like some advice as to what I should do at this point to save these trees. They are beautiful mature trees and I do want to keep them.

Any advice would be greatly appreciated.

Thank you
Tasha

Brent Ferris

What kind of soil overlaid the slate? If it was clay, the pine probably won't survive. If it is sandy loam or sand, there is a chance. And the mature oaks have what trunk diameter?

THe best option would be to remove the soil and slate -- an onerous job.
You may be able to save the trees by drilling a series of holes - preferably 1 1/4 to 2" diameter -- at least down to the previous topsoil, even better to the slate to be sure of accessing the root zone. You can use 1" -- just need more holes.
As a rough rule of thumb, the roots of the trees grow out from the trees about 3 feet for every inch diameter. (The old pictures of trees having carrot roots is a myth)
So, if your mature trees are say 30" in diameter, figure the roots to go out about 90 feet in all directions - probably your whole yard once you allow for all the trees., So set up a grid, and drill holes at 1 x 1 foot spacing. THis is a LOT of holes, and after the first 100 or so your back will be asking you if removing the soil wouldn't be easier.
You want to remove the soil you take out of the hole.
When I do this job, I generally fill the holes with peat moss (often some sand), some leaf compost, and add some liquid seaweed and other beneficial nutrients to the mix. If you can find mycorrhizae, add them as well since they help the roots absorb nutrients, The idea is to enhance aeration and provide extra nutrients to the root zone.

You can have someone else do the job -- and if so, a hammer drill bit does least damage to roots you might impact. I generally charge by the hole, plus materials. It is not a fun job, and we usually figure about 600 holes per day is a good day. It is best if one person drills, and one removes the soil and adds permeable material. It is very hard on the back for both people. But I have achieved good results.
Good Luck!!!

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Eric Frei

Restore as much of the original grade as you can.

You wrote:

That's plenty of depth, trees have the majority of roots (90%+) in the top 1 foot.

The ones you have smothered and choked in the top 6" are the real important ones, the fine hairy ones you can barely see .... they gather the resources.

Collar rot and dieback/decay of large anchor roots might take place over many years. During that time adventitious roots will grow from the stem supplying the tree, so you get green healthy looking trees falling over.

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