Dan Musicant wrote:
My very large plum tree is north of my tomato plot and the branches
overhang the northern most tomato plants (the trench for the tomatoes
runs north and south). Even if and when I trim the tree boughs (so
sunlight isn't intercepted), the roots invade the root space of the
northern most 1-2 tomato plants unless I insert barriers to keep the
plum tree roots out. Unless I block tree root access, the northern-most
tomato plant or two are pretty scrawny. Last year, the barrier was
fairly effective, it will be less so this year because the thin veneer
plywood material is decomposing in spite of the wood preservative I
applied when inserted last year.

I'm looking for a material I can use for a root barrier that will last a
few years, maybe last indefinitely. Can I pick up something at Home
Depot or Orchard Supply Hardware that I can maybe cut into pieces with a
jigsaw and use for a root barrier that will last a while?

What about a sheet of acrylic? I use one as a cover on a small pond,
and it's sturdy enough to hold up to being picked up and put back on
every day, and having raccoons sitting on it every night. Look for a
sheet that's thick enough that it won't bend and snap easily. Bonus -
it's lightweight and easy to handle.