Large tree roots

benaforceJanuary 31, 2010

I am trying to landscape a new yard. I have 2 problems. The yard is really low lying and retains water and i have a large Water Oak tree up against my back fence. I would like to landscape around the tree but it had huge roots that are above ground. Can I build up the dirt around the tree and cover these roots? Any ideas would be great.

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Raising soil levels may have a detrimental impact on the tree, if it's not done properly, and most likely will change your Site drainage. That water that pooled there now has to go somewhere else.

    Bookmark   February 1, 2010 at 9:13AM
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mtny(SW MT zn 3)

from your discription it sounds as if the exposed roots are mature anchor roots so raising soil level would probably not harm tree in and of itself.... however raising the soil level to cover those roots could result in some issues, it sounds as if this is a damp location....covering roots could exacerbate drainage problems....possibly encouraging fungal colonization or even drowning of the tree.....perhaps you could plant among the roots....bulbs are wonderful naturalized in and around tree roots , ferns too can lend themselves to planting among roots, hosta and other shade lovers could be options....this would be one way to integrate the tree into your landscape, creating a transition zone from nature to the domesticated landscape.....the plants will also utilize some of the excess moisture

    Bookmark   February 1, 2010 at 1:12PM
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I lived in the land of water oaks for 14 years and developed great respect for these trees. As chairman of the Grounds Committee on a large plantation I had to deal with them all the time. They fall over for no apparent reason. One crashed about 20 feet from me on a day with no wind as I was taking my morning walk. It was quite common to receive a resident phone call alerting me to a downed water oak across a road on the plantation. This probably will not happen to you as your tree sounds well anchored. Suggest you not add soil around the roots. Plant young stock in among the roots with minimum disturbance. Be patient. It will grow hiding the root network.

    Bookmark   February 1, 2010 at 2:12PM
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karinl(BC Z8)

What I understand from a brief scan through an internet search, these trees have no tap root and a very shallow root system (and confirmed: very unstable). My guess is that they way they adapt to a wet site is for the roots to grow high to retain access to oxygen.

If you bury these roots, and reduce their access to oxygen, I'm making an amateur guess that the tree will have to make some adaptation in order to continue getting air. For example, if the new soil also becomes waterlogged, it may develop new surface roots and let this set of more substantial roots atrophy.

If you want to keep the tree, you're probably wisest to just plant around the roots as suggested above with plants that can handle the conditions, without altering the soil level. If you want to address the drainage issue, that might involve getting rid of the tree. Personally, from what I've just read on line, I'd be inclined to get rid of it, and then address the drainage issue if possible, and re-landscape altogether.


    Bookmark   February 1, 2010 at 3:39PM
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I'm surprised that previous posters did not make it more clear that raising the soil level around the base of the tree can have very serious long-term effects on the health of the tree. All trees, whether tap rooted or not, have the bulk of their root system concentrated in the first 12-18 inches of the soil and the vast majority of the feeder roots - the fine roots that are essential for the tree to access soil oxygen, nutrients and moisture - are located just below the soil surface. Adding any more than a couple of inches of soil over the root system can impede its access to oxygen and essentially smother the tree. The impact is slow and you may not notice any changes in the health or appearance of the tree immediately but 3-5 years down the road, you could very well have a dead tree on your hands.

It is a pretty simple rule of thumb and one that is also pretty well documented as to results - you do not change the grade or raise the soil level around the root system of established trees unless you do not value the tree.

    Bookmark   February 2, 2010 at 9:43AM
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toronado3800 Zone 6 StLouis(6)

Personally I wouldn't take the chance in my yard. BUT, if the tree won't be falling on a house or anyone's costly possessions.....

I bet trees which tolerate frequent flooding are used to sediment build up. So it would be an interesting experiment to see if an inch of soil every other year would bother it.

That or raise maybe 1/8 of the area around the drip line every year or two.

Still notice I'm suggesting this experiment as a last ditch effort on your property not mine.

    Bookmark   February 2, 2010 at 2:23PM
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karinl(BC Z8)

It's a good point. I was focussing on stability, with what I hoped was an implicit understanding that a fallen tree is a dead one, but more emphasis was no doubt required on the outcome. You are quite right to suggest, if I'm interpreting correctly, that one can also kill the tree without making it fall down. But stability seems to be such an issue with these particular trees that I think falling would precede tree death, so that was where I focussed.

More could certainly have been said, and asked.

It was not made clear in the OP whether the tree is owned by the OP or by the neighbour, nor whether structures are within range. Those factors influence liability if an accident or tree death were to occur. People have been held liable for killing their neighbours' trees to the tune of tens of thousands of dollars. If the tree were not only to die but also to fall and on the neighbour's house at that, the liability would be astronomical.

But a brief scan of the internet was enough to convince me that I wouldn't have that species of tree hard up against my back fence in any case, once it reached a good size, especially with wet soil which is well known to have less tree-holding ability to start with. Bring up a strong wind, and wet soil might as well be cake batter for all the grip it has on roots.


    Bookmark   February 2, 2010 at 2:35PM
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Embothrium(USDA 8 Sunset 5 WA)

Use very light highly aerated soil and keep it off the trunk. Avoid gouging or barking roots or trunk to dig planting holes.

Or just mulch the parts where the roots come out of the ground, plant elsewhere in the vicinity.

    Bookmark   February 2, 2010 at 6:10PM
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I have related question here.
I am considering buying a lot with huge oak (Quercus robur), surely over 100 years old, its trunk is like 1,5 meters is diameter, and tree crown is around 16 m in diamater.
I'd like to build a house there one day and the question is what is the closest safe distance from the trunk to the house, that guarantees that the tree will be safe?

Here is a link that might be useful:

    Bookmark   February 3, 2010 at 7:18AM
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karinl(BC Z8)

Feel free to start a new thread with your question so that responses come to you rather than to the other person who posted. Also, then people don't have to read a bunch of other discussion before they get to your question.

You might also consider the Trees Forum, although you may get some discussion here.


    Bookmark   February 3, 2010 at 1:47PM
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