Tree pit mitigation strategies?
March 3, 2012 10:49 AM Subscribe
Previous homeowners built concrete retaining walls around trees in the backyard, creating large tree pits. How do we fix this?
We haven't moved in yet, so here's my only photo of the situation. The previous owners must have gotten a good deal on concrete blocks, which they've used to make gigantic rings around the trees in the backyard. The second ring in the background of the photo is much larger and surrounds a deciduous tree of unknown type. I assume the grass grew poorly in those areas anyway, and the level ground around the pits is easier to mow. However, these pits are huge, awkward, and sometimes deep, so we want to do some pit mitigation. Any ideas?
The local university says that putting dirt on top of tree roots is a bad idea, and the land itself used to be swampy, so everything is prone to settling. I'd like to make the rings smaller to gain some walking room around the house, and maybe try to grow some shade-tolerant groundcover plants to move away from the current seas of mulch. Have any of you conquered a similar situation?
We haven't moved in yet, so here's my only photo of the situation. The previous owners must have gotten a good deal on concrete blocks, which they've used to make gigantic rings around the trees in the backyard. The second ring in the background of the photo is much larger and surrounds a deciduous tree of unknown type. I assume the grass grew poorly in those areas anyway, and the level ground around the pits is easier to mow. However, these pits are huge, awkward, and sometimes deep, so we want to do some pit mitigation. Any ideas?
The local university says that putting dirt on top of tree roots is a bad idea, and the land itself used to be swampy, so everything is prone to settling. I'd like to make the rings smaller to gain some walking room around the house, and maybe try to grow some shade-tolerant groundcover plants to move away from the current seas of mulch. Have any of you conquered a similar situation?
One reason for putting concrete retaining walls around trees is to contain the trees, if the trees are invasive (e.g. many species of bamboo). I would identify both trees before undoing this work.
posted by feral_goldfish at 12:36 PM on March 3, 2012
posted by feral_goldfish at 12:36 PM on March 3, 2012
Best answer: If you change the grade of the trees, they will die -- quality topsoil or not. (like it says in the "keep existing grade" section of your link.) A standard tree protection detail will show construction fencing around the drip line of the tree to ensure that no grading is inadvertently done to a tree during a project. (other link here)
If I were you, I'd hire a professional (landscape architect) to help you solve your drainage and usability issues.
posted by Kronur at 1:49 PM on March 3, 2012 [1 favorite]
If I were you, I'd hire a professional (landscape architect) to help you solve your drainage and usability issues.
posted by Kronur at 1:49 PM on March 3, 2012 [1 favorite]
Best answer: There might be a bunch of flowering bulbs in that enclosure.
posted by Mr. Yuck at 1:58 PM on March 3, 2012
posted by Mr. Yuck at 1:58 PM on March 3, 2012
Best answer: This advice will do you no good if you are not a patient person. Since you are moving into a new house, you need to see what the trees look like in full leaf in June or July before you do anything out there. As Mr. Yuck mentioned, there may be all sorts of surprises awaiting you.
Have an arborist come out about the first of August and show him/her the photos you have taken every week from spring until midsummer, then decide what to do.
posted by halfbuckaroo at 2:03 PM on March 3, 2012 [1 favorite]
Have an arborist come out about the first of August and show him/her the photos you have taken every week from spring until midsummer, then decide what to do.
posted by halfbuckaroo at 2:03 PM on March 3, 2012 [1 favorite]
Response by poster: Thanks, everyone - I am more than willing to be patient and see what the trees do this summer! I am 99% the big deciduous tree is a normal Minnesota tree (ash, linden, elm, cottonwood, etc.), so nothing as exciting as bamboo. If it is ash, it may turn out to have a much more limited life span anyway, due to the ash borer. I will leave the pits alone and pour my landscaping efforts into the vegetable garden.
posted by Maarika at 5:08 PM on March 3, 2012
posted by Maarika at 5:08 PM on March 3, 2012
OK! So now you have to show us the pictures as it comes to life :)
posted by halfbuckaroo at 5:45 AM on March 4, 2012
posted by halfbuckaroo at 5:45 AM on March 4, 2012
Response by poster: Final update: To our great astonishment, when we moved in this spring we discovered tons of ostrich ferns and bleeding heart plants in the tree pits. Our friends call it "ferngully." So Mr. Yuck was on the right track - things did indeed pop up there. I planted some blackberry shoots that I got from a friend in the sunnier part of the tree pit, too.
We had an arborist come by, and we learned that the biggest tree pit is around an ash tree, which we've opted not to treat for the ash borer infestation. When it dies 10-ish years from now, we'll fill the pit and plant a new shade tree somewhere else in the yard (without a pit!).
posted by Maarika at 7:47 PM on May 29, 2012
We had an arborist come by, and we learned that the biggest tree pit is around an ash tree, which we've opted not to treat for the ash borer infestation. When it dies 10-ish years from now, we'll fill the pit and plant a new shade tree somewhere else in the yard (without a pit!).
posted by Maarika at 7:47 PM on May 29, 2012
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Reading the your second link, I think the big no-no is dumping a bunch of low quality fill dirt (e.g. mostly clay from a basement excavation somewhere) on top of your tree roots and declaring that you "got 'er done!" If you covered them with a quality top soil and did it in phases, so the trees had time to respond to the extra dirt, I don't think you'd have the issues they're describing.
Another possibility would be to open up the rings and embrace a heavily contoured yard. Adding a path and some steps using permeable blocks would give you the sort of roomed effect that zoos, amusement parks and the like often use to make their grounds seem bigger than they are.
posted by Kid Charlemagne at 11:56 AM on March 3, 2012