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LawnLad
08-27-2002, 09:08 AM
I went to visit a customer last night regarding a problem with a new bed we installed. The site of the bed is the location of an old 48" oak tree that fell in a storm (on the house none the less). Most of the stump was pulled from the ground and was hauled out by the tree contractor. The remaining root flare and stump were ground out by the tree company - they did a pretty good job. At best this was about 10" below grade. The tree sat next to the driveway on the higher side of the lawn.

Once the stump was ground out we hand dug the stump grindings out and hauled them off site (about 3 to 4 cubic yards). We dug down to solid soil. We added about 3 yards of top soil to fill the hole in last fall before the winter.

This spring we rototilled in 3 or so yards of leaf humus into the top soil as she wanted a perennial bed. The completed depth of the bed was about 8" thick (lots of air!). The bed is about 400 to 500 square feet in size I'm guessing - 16 x 25 ish.

The low side of the bed is next to the low point in the lawn which now collects water in the absence of the huge oak that is no longer pulling water. As well, she's watering now more than she did before since she has perennials in full sun that she never had before.

Now after time the bed has settled a bit. I dug a profile and found about 6" of nice bed material (may have a bit too much organic matter - have not tested volume yet) and under the organic matter is blue clay - with the wonderful odor of anarobic decomposition. Ummmmm good.

I think I have a perched water table... drainage is poor, plants are dying and I have a wet bed due to both poor slope/grade and over watering.

I need to correct the soil/bed. We're considering drainage for the rest of the back yard and I was thinking of running a couple of veins through the bed just to be safe. Then we would redo the perennial bed and re plant. But how do I change the soil profile? I remember from a class oh way back when we asked the prof the same question and he said - Mother Nature and time. I have control of niether.

Any thoughts on my problem would be appreciated. Thanks.

KenH
08-27-2002, 04:23 PM
Hey Lawnlad---
"But how do I change the soil profile?"

As you know, this is basically impossible. Might be a stupid question, but why doesnt she just cut down on the watering?? It seems like it would be ALOT more cost effective than laying drainage (also less headache).. She will have to find a happy medium where the perennials get enough water yet there is no standing water. Might be worth a shot as a first resort.

lawnstudent
08-27-2002, 10:56 PM
LawnLad,

discolored soil as you describe is an indication that the soil is excessively wet and has a lack of oxygen. This does not happen over one year's time. It is not due to the recent change in watering or the felling of that oak. You have a high water table, maybe a perched water table.

I think you have two options if the customer's heart is set on a perrenial bed at that site. 1) select perrenials that can tolerate wet conditions and shallow rooting. These would be wetland plants. Sedges. Cardinal flower. Etc. 2) Place drains under her perrenial bed and drain the soil to a depth that allows her perrenials to exist at that site. Ammend each perrenial hole with gravel, peat, sand, etc. based upon the needs of the perrenial. Good luck.

jim

LawnLad
08-28-2002, 11:24 AM
Thanks Ken and Jim. The water was never noticable before since the tree was actively soaking up water. When we get a big rain - a large pool of water collects in the low spot of the yard next to the bed and sits there. The bed that is now a perennial bed used to be ground cover next to the trunk.

I think drainage will help - and the suggestion of amending each perennial hole and selecting plants that will tolerate wet soil are good suggestions.

Thanks.

gvandora
08-28-2002, 12:11 PM
Perhaps you could encourage her to plants some new trees there. They could pick up where the large oak left off. Obviously the water requirements of new trees would not be the same of a well established oak, but atleast it would help.