Gravel RV pad full of weeds

Asked December 23, 2016, 10:38 PM EST

We have a large gravel RV pad in our backyard that is full of weeds and I mean FULL of weeds (we bought the house a year and a half ago). How do we get rid of them? We want to create raised garden bed boxes in that area, by just leaving the gravel and building on top, or removing the gravel. Second question, would it be okay to just build the gardens on top of the gravel or should we remove the gravel?

Salt Lake County Utah

1 Response

Let's start with your second question first. I believe that you would be better off to build your raised garden boxes on top of soil, rather than on the gravel. The reason for this is that the coarse gravel will actually create a perched water table at the bottom of the soil in the boxes, whereas regular soil should allow the boxes to drain better. That may sound counter-intuitive, but the water moves through soil as capillary columns, and the longer the columns, the better the drainage. If you break the columns by going from a fine texture (box soil) to a coarse texture (gravel pad), the drainage is decreased.

Controlling the weeds will depend on the type of weeds they are. If they are annual weeds, you will control them somewhat through the process of removing the gravel and regrading the soil. If they are perennial weeds, it will be more difficult because they will come back from the roots. I would do the following:

1. Remove the gravel.
2. Put your boxes in place and fill with soil.
3. Add 3-4 inches of mulch to the areas between the boxes. You can also put a weed barrier under the mulch that should help keep it weed free.
4. Plant your garden in the spring and then watch and see what weed problems occur. I would control weeds outside the boxes by hand, or by using a glyphosate herbicide (Roundup) as a direct spray to the weeds. If the existing weeds are annuals, they should not germinate and come up through the boxes, so it will just be a matter of controlling whatever is in the soil that you fill the boxes with. I would weed the boxes by hand until you have a better feel for what kind of weeds they are.
5. DO NOT use a soil sterilant on the old pad. It will stay in the soil for years and roots from plants in the boxes will contact it and the plants will be damaged.

Here is a publication that might be of help:
extension.usu.edu/files/publications/publication/Horticulture_Garden_2012-01pr.pdf

Hope this helps! Thanks for the question.