I have a old pine tree in my front yard, I love it, it is so large, the problem is it has large woody roots above ground, would it hurt it if I was to build a wall around the base maybe 9 to 12 inches high and backfill some garden soil? My yard is small and that would make a good spot for a shade garden. I have some plants under it now but they are hard to get started because of the large roots above the soil.
I had a tree company out to cut some trees and asked about adding soil under my big water oak tree that had a few exposed roots. The guy said I could put about 6 inches on them but no more. Don't know if that would apply to pine trees but it hasn't hurt the oak.
I don't know about water oaks specifically, but a lot of other oaks would not do well with 6 in of soil piled over their roots. I'm not sure what sort of credentials this tree guy had beyond knowing how to prune...if he was a certified arborist then he probably knows what he's talking about but if he was just a tree trimmer I would have suggested getting some second opinions before doing anything. Just because it hasn't hurt it yet doesn't mean anything (assuming this was something you did recently, vs something done a number of years ago. Damage from piling soil over the root zone won't show up right away, it's one of those things that can take years and when you start to see symptoms you might not even think to connect it back to piling soil up over the roots. Unfortunately by the time you start to notice symptoms it can be too late.
Stars...call your local extension agent, they are listed in the government pages, (counties) and they are free. They might come out and look or just have you describe, and then give advise on solutions. They also have handouts with great info on trees, lawns, baking, canning, veggies, just scads of info. Any growing info would be for your local area. Since your in a larger city could also see if there is a city forester, again in (city listings).
Normally it's not good to mess with roots of established trees, usually the problem is people buy containered trees which were planted too deep in the pot, they don't know any better, plant it and loose it later cuz it was just too deep. Only a few inches doesn't seem like much, but can be the death of the tree and why take the chance on such a great investment.
If you truely want to plant under your tree, How about some small groundcovers or better yet something that will reseed?
The soil line for trees is just above (only about an inch or so of soil), the upper most root, or the first root.
Not to worry, ecrane. He was a certified arborist. I trust his opinion. And this was about 5 years ago. I've had this same company out several times over the years. They do excellent work. They send a crew of about 5 guys with bucket trucks, chipper, stump grinder, bonded, insured, the works. When they leave, you never know they were there. Everything is neat and clean. And I have learned a heckuva lot about trees during their visit. But, as I said, I don't know if the same coverage depth would apply to pines. However, I'm getting ready to do the same thing myself. Years of running rainwater has exposed some of the roots around a large pine tree. It stands alone at the beginning of the woods in the back yard. I want to put flowers underneath it, some kind of vine on it (I'm thinking maybe hyacinth bean, morning glory ... maybe even a clematis), and a mimosa tree in front of it because it's one of those southern pines that has a long, bare trunk up about 20-25 feet. Maybe more. Nothing will be planted at any considerable depth except the mimosa tree which is in a one-gallon pot. I will try to find space between the roots to plant that, if any big ones go out that far. Will let you know how it goes and send pictures if I can. Here's the lonesome pine about two years ago ...
Glad your guy is a certified arborist, his opinion would be more trustworthy then. I've just seen too many tree trimmers around here who really shouldn't be trusted to do much of anything else (and in the case of some of the trimming jobs I've seen, I'd argue they shouldn't even be trimming trees!)
I wouldn't be surprised that his advice applied to that particular oak in that particular location and not a general thing. I suspect that pines would like it even less because they are more shallowly rooted that oaks. The problem with burying tree roots deeper is that you reduce the oxygen they get.
You could be right, Doug. I noted on purpose that the six-inch rule might not apply to pines. I have a "rooty mess" in my yard because many decent sized sweet gum trees were removed and their roots are still there. It's hard to tell sometimes which roots belong to which trees. Some of those roots you see that are a good distance removed from the pine may not be pine roots. I'm just going to have to play it by ear and hope for the best.
I have very old maple trees that have exposed roots. Years ago I planted hostas around them without adding soil. They seem to be doing well. For the really hard places (where there's not much dirt) I just used small starts which eventually got large. For the roots that are exposed on the walkway I "planted" flat rocks to meet the roots so you don't trip on the root. One root has lifted part of my cement "rocks," but that's just part of the character now. I love the tree more than the grass.