"brooklyn1" wrote in message news:%YYRl.312
Unless one already has the plywood exterior ply doesn't come cheap... and
a 4' X 8" plot is not much gardening space... I'd not bother with less
than six sheets. And you still need to till, pick rocks, rake, amend, and
till and rake again, and again.

Well, no you wouldn't. If you start off by smothering the grasses with
plywood or some other solid surface, then you shouldn't till at all after
that. Tilling will just bring the submerged weed seeds to the surface and
you'll have the same problem over again. It's much better to smother
everything under where you want to plant (letting the old plants rot and add
nutrients to the soil), and then build on top of that to make new,
relatively weed-free soil. This is why I would advocate cardboard instead
of plywood (since cardboard can be left in place to decompose), but the
plywood *IS* a good idea if you can get it and don't mind moving it when it
comes time to plant.

A good deep rototilling will dispatch any weeds/grass so that those will
never grow again...

A good, deep rototilling will also dredge up dormant weed seeds and bring
them back to life. With my clayey, weedy soil, I have found it infinitely
better to leave the tiller in the garage, and just pile organic stuff on top
of cardboard to make rich, fertile garden plots that are virtually
weed-free.
--S.