Raised beds over lawn - Ask Extension
Hello,I am planning on putting some raised beds over top of existing lawn. What is the best way to accomplish this? I have purchased some landscap...
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Raised beds over lawn #231590
Asked March 18, 2015, 9:06 AM EDT
Hello,
I am planning on putting some raised beds over top of existing lawn. What is the best way to accomplish this? I have purchased some landscape fabric. Is that sufficient to kill the grass underneath the raised beds? Also, the area is not level. There is a slope where I am planning on putting the raised beds. What is the best way to level the area?....and with what material?
Thanks for any help.
Karen
I am planning on putting some raised beds over top of existing lawn. What is the best way to accomplish this? I have purchased some landscape fabric. Is that sufficient to kill the grass underneath the raised beds? Also, the area is not level. There is a slope where I am planning on putting the raised beds. What is the best way to level the area?....and with what material?
Thanks for any help.
Karen
Multnomah County Oregon
Expert Response
Building raised beds over the top of an existing lawn is a great way to start vegetable gardening. There are several things you should take into account when deciding how to proceed. First, how deep will the beds be? If the sides of your raised beds will be low (4-10" tall), for the best results you'll need to dig and loosen several inches of soil below the area where you intend for the beds to sit. If your beds will be at least 12" high on the sides (and thus, filled with at least 9" of soil), it is not necessary to dig and loosen the soil beneath the beds (although it can't hurt to lightly fork the soil below and then saturate it with water before filling the beds with your new soil mix).
Regarding the grass,if your beds are shallow, it would be best to dig the grass off entirely and then begin loosening the soil below. The landscape fabric would help prevent the grass from growing up, but of course it would prevent the vegetables' roots from growing down. If your bed will be deeper, you can just thoroughly water the grass inside of the beds before burying it with several inches (9 or more to be safe) of good quality soil mix. The grass will be so smothered by the soil that it will compost itself and provide food for the worms, insects, etc. and (eventually) make your soil all the more rich.
As for the issue of slope in your yard, I am not sure I can be of much help with that without knowing more specifics. Some ideas include 1) building the beds to accommodate the slope (i.e. shallower at one end (for lettuces, radishes, etc) and deeper at the other end (for tomatoes, potatoes, etc.). 2) Excavating or hand-digging the yard so that it is level. 3) Adding several yards of soil to the area to level it out (which would be tricky, as the soil would compact considerably over time). A final option would be to choose not to use raised beds at all, but rather to build a terraced garden that would take advantage of the existing slope.
Here is a link to a very comprehensive document on vegetable gardening provided by the Oregon State Extension Service. I hope you find it useful.
http://extension.oregonstate.edu/deschutes/sites/default/files/em9027complete1.pdf
Regarding the grass,if your beds are shallow, it would be best to dig the grass off entirely and then begin loosening the soil below. The landscape fabric would help prevent the grass from growing up, but of course it would prevent the vegetables' roots from growing down. If your bed will be deeper, you can just thoroughly water the grass inside of the beds before burying it with several inches (9 or more to be safe) of good quality soil mix. The grass will be so smothered by the soil that it will compost itself and provide food for the worms, insects, etc. and (eventually) make your soil all the more rich.
As for the issue of slope in your yard, I am not sure I can be of much help with that without knowing more specifics. Some ideas include 1) building the beds to accommodate the slope (i.e. shallower at one end (for lettuces, radishes, etc) and deeper at the other end (for tomatoes, potatoes, etc.). 2) Excavating or hand-digging the yard so that it is level. 3) Adding several yards of soil to the area to level it out (which would be tricky, as the soil would compact considerably over time). A final option would be to choose not to use raised beds at all, but rather to build a terraced garden that would take advantage of the existing slope.
Here is a link to a very comprehensive document on vegetable gardening provided by the Oregon State Extension Service. I hope you find it useful.
http://extension.oregonstate.edu/deschutes/sites/default/files/em9027complete1.pdf
