How long before removed tree stumps flatten

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bwaynef
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How long before removed tree stumps flatten

Post by bwaynef » October 10th, 2020, 9:56 pm

I just had a bunch of trees removed and find myself having the opportunity for a lawn again. I used to have a nice organic tttf lawn at a previous home and would like to go that route again. It's INCREDIBLY tempting to start it soon, and I may have JUST enough time to get it in before my first frost, but it'll be pushing it.

My concern has to do with the piles left from where the tree stumps were removed. I suspect they'll reduce down over the fall. Does anyone have an idea how long before the lawn will flatten out? Is there anything I should do to ensure a smooth lawn? Is it wise to wait before sowing seed until the tree stump areas have flattened?

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andy10917
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Re: How long before removed tree stumps flatten

Post by andy10917 » October 11th, 2020, 7:42 am

Depending upon what you mean by "flatten", the answer could be anywhere from 4-6 months to a decade. We'll need much more information to give you some guidance and an answer that isn't all over the board.

If you're asking how long the soil will take just to settle, that's in the 4-6 months timeframe. But there is a a whole root system below the soil that's going to decay over time, and you'll experience it going from mounded soil to depressions as that happens. If the trees were smaller softwood trees with 6" trunks, you'll see the soil "sink" somewhat for 2-3 years, but the process could go on for up to a decade if the trees were 18" trunks of hardwood trees.

Did they do stump grinding, and is the mounded soil a mix of soil and wood chips? How big were these trees?

Let's start with those questions...

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ken-n-nancy
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Re: How long before removed tree stumps flatten

Post by ken-n-nancy » October 11th, 2020, 8:24 am

I concur with Andy's questions -- big variation depending upon what constitutes the mound, and how much of it is wood chips. Ultimately, the wood chips decay away to practically zero volume over time.

Posting a picture might help, although it's really hard to see shallow depressions in a still pic. A video is practically needed to see depressions effectively.

My personal preference, when trying to put flat lawn over where a tree used to be is to remove as much of the old stump as possible (to about 12" below ground level), remove all of the mixed wood/soil, and then fill with dirt. Even then, as Andy mentions, the roots below will decay and a depression will result. I have a place where a tree was removed in our back yard -- probably one of about 14-18 inches in diameter, and even with removing everything to about 6" below ground level, that area was still sinking 5 years later. I've added soil to that area twice now, both times by cutting off the sod, adding soil underneath, and replacing it, but it's still a bit lower by more than an inch. I'm hoping the next time will be the last time...

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andy10917
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Re: How long before removed tree stumps flatten

Post by andy10917 » October 11th, 2020, 8:35 am

Yup, when I purchased my home, there were two very large maples that were too close to each other and neither was thriving. I had one removed, and the soil behaved exactly as K&N describes. It played out for 10-12 years.

bwaynef
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Re: How long before removed tree stumps flatten

Post by bwaynef » October 11th, 2020, 1:30 pm

All this talk of 14-18" is cute. We had a white oak removed that my family of 6 can probably stand on the trunk that's left, sawn off at just above ground level. Granted, it was the largest, but these were mature oaks (mostly) that were removed. This one was also the only stump that wasn't ground, since they couldn't fit the stump grinder inside the fence in the back yard. I'm not concerned with the lawn around that trunk ...right now.

The rest of the mature oak (mostly) and hickory/elm (just a few of the smaller ones) stumps were ground and there are mounds left where the stumps were. Those mounds of fluffy soil and stump-grindings are what I'm interested in knowing how long they'll be around. Also, I suppose based on the size of these trees and taking you guys' comments into consideration, I'm in for a decade-long settling ...after the initial 4-6 months. For a tttf lawn, is it best practice to dig it up, back fill, and lay the grass back over that? I know bermuda (and warm-season grass in general?) you can just put out sand to level things.

I'll have to figure out how to manage pictures. Thanks for the information.

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