Magnolia roots growing up?

11 years ago

I have a magnolia growing *directly* next a retaining wall. The magnolia is well-established, about 10" diameter. The wall is about 3-3.5' high.

I'd like to back that wall a couple of feet away from the tree.

From what I read, magnolias have fairly shallow root systems. If the roots on the "high" side of the tree are only 18-24" deep by soil depth, that places them 1-2' *above* "level," higher than the actual root flare. Will magnolia roots grow against gravity? Am I risking exposing some of the tree roots by moving that retaining wall away from the tree?

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Comments (5)

ken_adrian Adrian MI cold Z5
11 years ago
i have read this 3 times.. and i just dont understand ... what you are trying to say ... [dont worry.. its probably me ..]

a ten inch diameter trunk.. will be supporting a tree.. what.. with a 20 foot canopy ...

conceptualize that its root mass .... is twice that ... in a root form.. not the form of the tree ...

what you will be doing.. is severing a line of its roots back where you will be putting the foundation of your wall .. [you do not say its a retaining block wall with little or no foundation] ....

so in my mind.. your question should be whether digging out a few more feet.. in a straight line cutting all the roots back there.. will have a major impact on a very large tree ...

and frankly.. we can all do our best chicken little act on how its no good.. but until you do it ... no one will really know .... its your call ...

so i am really wondering.. how you worked gravity into the equation ... lol ...

now .. all that said.. you 'SEEM to indicate that you are moving this wall for the sake of the tree ... and that makes no sense to me at all.. a tree that grows to that size is having no issues with that wall .. so why do you??? .. you may be trying to fix something that isnt broken ....

a picture would sure help us understand where you are going with this ...

good luck

ken

ps: a tree puts its roots where it is most advantageous for vigor.. and if it takes defying gravity ... i would bet my nickle.. they could find a way to do it.. lol ...
brandon7 TN_zone7
11 years ago
It's not a matter of the roots "defying gravity". It's a matter of them seeking specific soil conditions (oxygen, moisture, etc). If the roots were able to grow underneath the footing of the wall, they would surely head straight (well, maybe crooked) for the upper level of soil on the other side (high side) of the wall. Now the question is whether the roots have ventured under the wall, and by how much. That will depend on how the wall is built, the type of soil you have, and who knows what else. I don't know how to predict what has actually occurred without probing/digging in the area a little. If your current wall foundation is deep, you may not have many roots under the wall.
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Many thanks for your answers. What Brandon wrote ("[...] some magnolias grow a taproot first (as opposed to a more fibrous root network), but this initial taproot (not sure if there is a better word for it) does not develop into a pronounced taproot as the tree grows.") fits what this page says : http://forestry.about.com/library/silvics/blsilmaggra.htm "Rooting Habit- Southern Magnolia is a deep-rooted species, except on sites with a high water table. Seedlings quickly develop one major taproot. As trees grow the root structure changes. Trees of sapling stage and beyond have a rather extensive heart root system (i.e. several to many sunken roots grow down from the root collar of the tree trunk). Older trees may develop a fluted base with the ridges corresponding to the attachment of major lateral roots." Although I swear I saw a tap root on the one I dug up ! ;-) Well, it was a central, vertical and thick root, clearly distinctive from the rest of the (superficial and extensive) root system and going down to... I don't know because because I didn't entirely dig it up, but it was at least 40 or 50 cm (16 to 20 inches) deep. In heavy clay. Not an oak tap root, alright :-) Thanks again, Olivier.
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Embothrium
11 years ago
Demolish the wall without seriously whacking the tree (including the roots), then make the new wall where wanted. Again, without cutting into or banging the tree. Fill in with soil as needed, in order to maintain the grade at the right level for the tree. Do not bury the base of the trunk with a fill, or cover a large portion of the root zone with a fill. Around and beneath trees the main thing is to avoid compaction, cuts and fills.
Transplanted07
Original Author
11 years ago
@ken_adrian, good questions. The wall is not moving for the sake of the tree. The wall is coming down because it's hideous and slapdash. It's going back up (with better construction and nicer materials) because it's necessary. Perhaps I should have included this detail from the start, but my thought is not so much to back up the entire wall, but to rebuild it in two levels, terraced if you will. The lower half of the wall will likely remain where it is, but I'd like to push back the top half of the wall, which should help open up the whole space.

@brandon7, Thanks. I hadn't given much thought to the foundation of the existing wall inhibiting root growth in that direction. I'll have to take a good look at what kind of effects it has had.

@bboy, Thanks for the response. The wall is mostly dry-stacked, so demolition shouldn't be too chaotic around the tree. Thanks for the warning about fills.

All, thanks for the advice. It sounds like my best approach will be to proceed carefully, adapt to whatever root situation I find, and put together something attractive and long-lasting, while minimizing impact to the tree and roots.
suikerbos
8 years ago
Have a large magnolia, height of double storied house with trunk about a foot in diameter .Trunk is about 6-8 ft from road , which is being torn up for reconstruction. The larger surface roots seem to be on opposite side and parallel to the road. Smaller roots on the road side are being disrupted. Is it likely that the tree will be affected/ anything one can do . i.e. water the drip line?

Magnolia roots growing up?

Comments (5)

ken_adrian Adrian MI cold Z5

brandon7 TN_zone7

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Magnolia roots growing up?

Comments (5)

ken_adrian Adrian MI cold Z5

brandon7 TN_zone7

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