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Raised flower beds around trees

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willowdancer blog photos
Joined: 3/08/2009
Location: Tennessee
Posts: 89
Posted: Sep/16/2010 4:18 PM PST

I am planning on making a raised bed around the base of one of the big oaks in my backyard: the tree has a 3' diameter and seems very healthy *or at least it seems healthy to a person who has no clue about how to tell if a tree is healthy or not*

My question is will the moisture of the soil in the raised bed put the trees health at risk? I am worried that the soil making direct contact with the bark might cause it to rot and harm the tree some how. If the flower bed will cause damage to the tree, how might I go about preventing any damage to the tree while still having a raised bed? Is there some kind of liner I could use or something like that?

Attached is a photo of how far I have gotten with the raised bed. I need more rocks, lol. :-P


Any imput would be greatly appreciated :-D

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MamaBearBSA photos
Joined: 8/14/2002
Location: Altoona, Iowa (near Des Moines)
Posts: 4992
Moderator
Posted: Sep/16/2010 6:15 PM PST

Build two walls, like a doughnut, around the tree. Leave at least 6 inches from the bark to the inside wall, all around the tree. This will allow free air flow all around the bark.

The problem is, you won't get most rain to the bed. It takes a very heavy rain to get thru the drip line of the tree. It will require watering.
ga_girl photos
Joined: 8/02/2008
Location: Georgia
Posts: 1335
Posted: Sep/17/2010 4:49 AM PST

Raising the soil around a tree - not just the park that touches the bark - can be of concern because many of the roots are just under the surface. However, and correct me if I'm wrong, you appear to be only raising the soil about 3-4 inches?

That should not be a problem. It is adding 6+ inches of soil that would be of concern - people that want to significantly change the grade nearby, etc.

You can find various articles about this, but here is one (remove that space in the last word - treewells should be all together):

http://www.wvu.edu/~agexten/hortcult/treeshru/tree wells.htm
carolyncat353 blog photos
Joined: 4/29/2008
Location: Westlake, La
Posts: 10091
Posted: Sep/17/2010 6:04 AM PST

I agree about raising the soil level no more than 6 inches around the tree, and also about not packing it around the trunk. Be careful when mulching too, to not pack it around the trunk of the tree.
willowdancer blog photos
Joined: 3/08/2009
Location: Tennessee
Posts: 89
Posted: Sep/17/2010 6:53 PM PST

I was planning on raising the bed 10", I just dont have nearly enough rocks yet. I was aware of the need to water the plants because of the tree blocking the rainfall, but the bed is within easy access of the garden hose. I was going to plant fox's grape, lily of the valley, Hostas, Astilbes, bleeding heart, and Astrantia in the bed. This is my first attempt at growing any of these plants but my main concern with this shade garden is the saftey of the tree: I can always get more plants next year but the old oak trees in the yard cannot be replaced so easily. Will I still be able to have the raised bed like this if I do a donut-type frame for the dirt? After checking out the site ga_girl provided I think I am going to line the bottom of the raised bed in small rocks to allow water to drain away so it wont rot the roots. What do you all think of this? Are there any other measures I should be taking?

Thanks so much for all the input so far! Yall are ultra helpful!

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MamaBearBSA photos
Joined: 8/14/2002
Location: Altoona, Iowa (near Des Moines)
Posts: 4992
Moderator
Posted: Sep/17/2010 8:48 PM PST

With good drainage and the doughnut type frame, I think you will be fine.
willowdancer blog photos
Joined: 3/08/2009
Location: Tennessee
Posts: 89
Posted: Sep/18/2010 6:39 PM PST

awesome! thank you :-)

I will update on the progress of the raised bed in my blog as things progress
carolyncat353 blog photos
Joined: 4/29/2008
Location: Westlake, La
Posts: 10091
Posted: Sep/20/2010 9:19 AM PST

I'm not sure about the 10 inches over the roots. Somewhere (I'll look in my info at home) I was reading about how new construction damages trees, and what to do for repair. In this article, there was concern about bringing in topsoil for landscaping, and the author talked about the trees roots, that take in moisture and situated a certain depth in the soil, and adding too much on top would actually smother the roots, and not let them get the water necessary. Gradual addition of soil (over years) was better. But then again, I see new beds being made all over town around old trees and they seem to do fine.
MamaBearBSA photos
Joined: 8/14/2002
Location: Altoona, Iowa (near Des Moines)
Posts: 4992
Moderator
Posted: Sep/20/2010 12:03 PM PST

Carolyn, I think concern comes from construction equipment compacting the soil and then adding heavy clay soil on top. If she just adds a good soil/compost mix to the top the roots will be fine and if they need to they will migrate up. As long as the soil is not heavy and compacted.
willowdancer blog photos
Joined: 3/08/2009
Location: Tennessee
Posts: 89
Posted: Sep/20/2010 2:17 PM PST

There wont be any construction around the base of the tree: just me with my red wagon for moving rocks and dirt/ I looked around the base of the tree and there aren't any roots that are coming up towards the soil within the circle that I will be raising the bed on, or beyond that even. I also am not going to be digging into the ground at all because I dont want to disturb the roots and, quite frankly, I am lazy and would rather just pile compost and topsoil on top without having to dig any more than i have to, lol :P
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