By John Crooks, NHCLP
Mulch mounds – the goal must be to put mulch as high up the trees as possible. We have taken several yards of mulch from around trees and shrubs on two of our new accounts this year. This requires a lot of work due to all the roots that grow up into the mulch. This is one of the reasons you should not put that much mulch around the trees or shrubs.
Shrubs seem to get lots of roots growing up rather than out and deeper into the ground. Once this happens and the temperatures rise the mulch becomes very dry, which in turn dries out the roots that are in search of water and nutrients. The roots up there in the dry mulch will not find either water or nutrients and in turn the plant starts showing stress. The larger trees don’t seem to have a lot of roots growing up into the mulch but the mulch stacked way up the trees holds moisture around the bark of the tree allowing bugs and diseases to cause problems for the tree.
The reason the larger trees don’t grow roots up into the mulch is because the mulch that is placed around the larger trees never goes out to the drip line of the trees branches. Instead the mulch is placed right at the base of the tree. The mulch never goes out more than about 2 or 3 feet around the base of the tree.
The roots of these larger trees will not receive any value from having mulch placed around them like this. It would take a mulch bed of about 30 to 45 feet in diameter to even create any value and in some cases it maybe even larger. Then it is still important not to apply a deep mulch layer of over 3 inches.
The reason you never see mulch out this far from the tree is because it would be very costly. When trees are that large they should not need mulch applied for any reason as the roots should be able to get water and nutrients just like the trees out in nature do – by searching for it in the ground around them.
Their roots run long and deep in search of the water and nutrients they need. In nature the leaves that we all rake and vacuum up every fall are left to decompose into compost which breaks down and becomes nutrients for the tree and they cover the entire area under the canopy of the tree. The better thing to do would be to leave the leaves or to apply a layer of compost every year.
The question is always asked why people do this kind of thing to their trees and my answer has always been the same as it is today. They watch the top named landscaping companies installing trees and shrubs at large commercial sites. The landscaper puts the tree in the ground usually at less depth than the tree should be planted, creating a raised mound to begin with. Then they put that nice bowl around them just as it is shown in the trifold handed out by the UNH Cooperative Extension.
The bowl is there to help hold the water when you are giving the tree a good watering. The problem with this bowl (in my opinion) is that it should be removed in the fall before the ground freezes so that it does not hold water, which freezes around the base of the tree. This never happens.
The bigger problem with this bowl comes the next year when the next company comes in to mulch. They see the bowl as a good holding spot for mulch and, as we do with a bowl of soup, fill the bowl to the top. This means that the mulch is much deeper than it was intended to be when the tree was planted.
You may ask where I came up with this idea, so here is the answer your question. I have watched this happen year after year. You can tell that they are trying to do the right thing. One of the large companies I see doing this exact thing is a member of NHLA and some of their workers come to our conferences on a regular basis. I (as does others) watch what they are doing and over the years I watched what happens to these trees and shrubs after they are installed.
I have seen it year after year and last fall took some pictures of an install like the one I have mentioned above and was going to show a picture of it after mulch is applied, but they have yet to apply the mulch this year. When they do I will include the pictures in my President’s Notes.
For the above reason my company has stopped including the bowl when we are planting trees and shrubs. We have not found any issues where the trees and shrubs have been planted without the bowl, and it keeps future landscapers from simply filling the bowl. Which helps keep over mulching at bay and the trees and shrubs have a healthier and happier life.