Barrier in ground to ward off tree root invasion

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?
The trench I dig for my tomatoes is generally about 2 feet deep, because once I get to that depth (I virtually always do this some time in March) the trench has standing water when I get to about 2 feet. The soil is pretty heavily clay, so I work in loads of compost when I refill the trench, which I make myself. The barriers I've been putting in are about 2 feet (maybe a bit more) from top to bottom.
I might remove the tree, but of course that's a BIG job. Suggestions appreciated!
Dan
Email: dmusicant at pacbell dot net
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Dan Musicant wrote: ...

...
Move the tomatoes...
--
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Dig another trench and pour concrete with rebar or the reinforcement mesh.
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merger of state and corporate power." - Benito Mussolini.
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Dan Musicant wrote:

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.
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We had a similar issue with neighbors' roots invading. We used a scrap piece of metal siding cut with tin snips into a rectangle, and buried on long edge just below ground level. Worked for the couple of years it was in place before we moved, probably will continue to work for years.
Wondering if the paint/rust that might develop off sheet steel would be harmful to the tomatoes? probably no more so than any preservative that would come your plywood.
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In article

There is always "food grade" paint.
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merger of state and corporate power." - Benito Mussolini.
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wrote:
:We had a similar issue with neighbors' roots invading. We used a :scrap piece of metal siding cut with tin snips into a rectangle, and :buried on long edge just below ground level. Worked for the couple of :years it was in place before we moved, probably will continue to work :for years. : :Wondering if the paint/rust that might develop off sheet steel would :be harmful to the tomatoes? probably no more so than any preservative :that would come your plywood.
I actually have a sheet of aluminum, it being a sign I found. It would undoubtedly work, but I'd have to cut it (I think it's bigger than 2' wide), but it's not enough. I figure I need around 20 square feet. Well, at least 12.
I was thinking some kind of plastic, but plastic sheeting sounds like it might work. As long as it doesn't break or crack, that is.
Dan
Email: dmusicant at pacbell dot net
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wrote:
-snip-

Good time of year to call a place that installs ponds. That black rubber pond-liner stuff is pretty much indestructible.
Scraps might be available. A 2 foot wide strip would be useless to a pond install, but should suit you fine.
Dig a trench- tack a strip of this stuff to a 2x4- suspend into trench- fill trench- remove 2x4- forgettaboutit.
Jim
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: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? :> :>The trench I dig for my tomatoes is generally about 2 feet deep, because :>once I get to that depth (I virtually always do this some time in March) :>the trench has standing water when I get to about 2 feet. The soil is :>pretty heavily clay, so I work in loads of compost when I refill the :>trench, which I make myself. The barriers I've been putting in are about :>2 feet (maybe a bit more) from top to bottom. :> :>I might remove the tree, but of course that's a BIG job. Suggestions :>appreciated! :> :>Dan :> :> :>Email: dmusicant at pacbell dot net : :Consider a _ Bamboo Rhizome Root Barrier_ * : :"ProPlas Bamboo Barrier Film has proven to be an effective material :to prevent the unwanted spread of bamboo." : :At least 40 mil. : :http://www.professionalplastics.com/BAMBOOBARRIERFILM : :Perhaps even a pond liner would work.
This looks very interesting. It's expensive, though. If bought at this link, the minimum is 2' x 25' of 40mm. As it happens, I also have a problem with bamboo from the neighbor's hard, but I've just lived with the problem for many years. It would be a ton of work to install a barrier at the property line to keep out the bamboo roots. I don't let any of that bamboo get anywhere above ground, but there's no keeping the roots from invading. Unless, I install a root barrier.
In fact I only need a maximum of 10' of the root barrier to take care of the tomato vs plum tree problem. I figure I can probably score 10' of this or similar (they say it's polyetheylene) locally (I'm in Berkeley), or close to it,.
Dan
Email: dmusicant at pacbell dot net
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