Beds mounded too high?

(Question)

Hello Toronto Master Gardeners,

I am worried I made a big mistake when I set up and planted the trees and shrubs in my backyard. Along the fence-line around the backyard I mounded up the soil, and planted several shrubs and a couple of trees.

The garden has been in for about 5 years now. I am really worried that I mounded the soil up too high when I first planted the beds. I know it is not advisable to create a “mulch volcano around a tree when planting it. Could the mounded soil be doing the same thing? What can I do to help the shrubs I planted?

I went out this afternoon and took a few photos of the mounded bed I put around the fence, and planted shrubs in. As you can see I have begun lining the side of the mound facing the grass with stones. I wonder now whether I should abandon this idea and let the mound/berm spread itself out without having a heavy border in the way.

garden-04

(Answer)

Thank you for contacting Toronto Master Gardeners.

Planting a tree too deep can cause the death of a tree, slowly but surely.  The top of the roof flare (the base of the tree where the trunk becomes wider – just above the roots) should always be left exposed. This root flare’s natural curve represents the place where the roots branch off from the truck. The majority of roots will be found in the top 10 inches of soil in large trees, so the curve sends the roots off in the right direction. When roots are buried too deeply, less oxygen and warmth are available and create a girdling root situation.

You may be able to remedy buried trees by removing excess soil so that the root flare is visible above the soil line. The best way to correct a girdling root problem is to cut the root. Roots do not move in the soil so it will need to be cut to keep it from harming the tree later.

The issue is less important with shrubs which are multistemmed and can send up new shoots.

Good luck!

You may wish to refer to the following websites for detailed information: