Hi Paul, I also have a bermuda lawn problem and the only solution for me (I've tried many) was to put plastic under the box and cut holes for drainage in the plastic. It has to extend out from the box at least 2 inches. I usually lay down cardboard in the box to absorb most of the excess water. I also have tree roots and this helps. The weed cloth didn't work for very long, but it's 2 years now without a problem using the plastic. Hope this helps.
Kath

I'm about to build my boxes on top of bermuda grass also. My plan until recent posts about the subject was plastic in the aisles and lots of cardboard under the beds.

If you can keep the yards bermuda grass far enough away from the beds, will the weed cloth and/or cardboard last long enough to kill the existing grass so it won't come back in 2-3 years?

will the weed cloth and/or cardboard last long enough to kill the existing grass so it won't come back in 2-3 years?

The cardboard won't, the fabric likely will. Double the fabric IME. As I said elsewhere, the energy expenditure to foil the Devil's Weed of Doom! is seemingly never enough.

Dan

Thanks all for the input.
Martha, what kind of plastic do you use?
Paul

I put in 6 4x8x10 beds in 2004 and they went over bermuda. First I layered newpaper about 6 sheets all around and wet down then filled boxes and I have yet to have them grow in the boxes. I beleive if you do it while it is dormant probably makes a difference because it need lite to grow. Worked for me.