Raising soil level

[birdhouse-lady]

I've hear that raising the soil level too much around existing trees could kill the trees. How much is too much. I need to raise a bed that has three established trees in it approx 8 to 12"....how best to do this?

[opabinia51]

Well, good soil naturally contains auxins and giberellins (root stimulating hormones) that will encourage root growth in trees. So, if you go up by 3 to 4 inches maximum I don't think that it should be a problem.

How to do this?

Well, I'm a huge fan of doing the good old method of sheet composting, it's slowish but, it works and it benefits the plants (inlcluding the trees).

So, lay out layers of greens and browns (say, grass clippings, manure, etc and mulcheld leaves (apple and maple are the best)) Top off with manure (as a green).

Be sure to leave a few inches of space around the trees. As the material composts, you can move the newly created soil up against the trees.

[The Helpful Gardener]

But 8 to 12 inches can be deadly to most trees. Best not to do this...

HG

[Brad]

The biggest concern is applying a heavy textured soil (one with small pores) on top of a more "loose" soil. This is a sure-fire way to suffocate a tree over time.

[birdhouse-lady]

O.K. then, what if I build a rock or landscape timber barrier around each tree and only raise the soil level around the trees? How far out from the trunk would this barrier need to be? I just don't want to dig up the trees and risk losing them.

[Brad]

Anything deeper than 3-4" is probably going to be detrimental to the health of the tree if it is applied under the "drip line" of the tree. Make sure not to exceed 4" of a loose, non-compacted or clay soil. I hope I'm explaining this right. It reads kind of funny. Let me know if it is confusing and I'll try to clairfy.

[opabinia51]

It is interesting to note that my Aunt and Uncle have had an ongong compost pile around their walnut tree for about 30 years and the tree does fine.

Applying a mulch to raise the bed by a few inches is fine, but, leave the space around the trees as said. So, very slowly if you still want to, you can raise the bed, year by year.

[Brad]

I agree with you. Slowly and over a long period of time is the way to go. Especially with composting material. Its very loose, has a lot of pore space, and is a healthy material.

[birdhouse-lady]

Looks like Slow and Easy is the way to go. Lucky for me I haven't spread all my compost from the fall and winter yet and should have enough to start with a 3" layer. I will also do my mounding well between the trees and see how it goes. Thanks everyone. I sure am glad I found this site!

[opabinia51]

Glad to have you, keep us posted as to how things go. Be sure to give your trees some "breathing room" better to be safe than sorry.

Feel free to post any advice or questions at any time.

[The Helpful Gardener]

Landscape architects use tree wells if they need to raise soil around existing trees; building retaining walls around the dripline to keep the tree at it's planting level. While the soil structure of compost is more mulch than soil, it will eventually become soil but not at a rate that the tree cannot adjust to... SO, careful...

HG