wood products - sealing

Dear Forum,

I have enjoyed from the help in regards to deck treatment and the reviews. Very no nonsense and I appreciate it. Thank you all.

I have a parallel subject which doesn't fit the general titles of the forum, so please excuse me:

I am putting up a wood barrier between grass and an elevated flower bed.
I was told that there is nothing to do about rot over time if I have wood in the soil, but I can delay the rot if I wrap it in a protective plastic AND coat it with a sealer.

I understand that I will have to replace the barrier in the future, but which sealers would you consider to be appropriate for such a job?

The wood - is junk wood - just decorative.
the climate is desert like summers (i live outside of the US in the middle east) but I water the area every day. Winters are generally mild - I would say like Houston, TX - even less rain (the humidity is as high)

Because I am not in the states - some of the companies that are well - reviewed here on this site are not available - so if you offer an opinion - I would very much appreciate a couple options - so as to see what I can obtain here.

As an aside - I recently treated my pine deck with Flood clear stain emulsion, and it has been wonderful.

Thanks!

Michael