Hi Ania, if you are talking about the type of plywood boxes they use for packing into, I have a couple I have been using as a potting bench for 3 years (my husbands receives pumps in them for our business) and they have not fallen apart though they have aged to grey. They are open to the elements. I think I would line it but with what maybe the Wicking Bed people can help you with that one. Sorry to hear you had a bad experience but it is fun to start over again.
Ania you can line your box with builder's plastic. Buy from hardware around $2 a lineal metre and usually around 2m wide.
You will need to provide drainage or if you are doing a wicking bed you need one overflow hole.
Just ask if you want to know more about wicking beds. They can be very basic all you need is the plastic and some potting mix. There's some posts and photos on BLF if you want to see what I'm talking about before making a decision.
Yes hi there, if buying plastic make sure it is the heavy type builders plastic.I used it to lay under an above ground pool and could not believe how good its condition was after 6 yrs underground.Saying that I recently bought a pkt from bunnings I thought was builders plastic for a new wicking bed but when opened I found it to be very thin and it stunk of poison.Naturally I didnt use it so ask if in doubt.
Sorry about the damage last year. Good news about your fruit trees though. I'd definitely line the box, even if it's made of marine ply. Remember, the size lining you need will be:
width: 60 cm + 60 cm (for the two sides) + however wide the box is (and a bit extra to be safe).
length: 2m +1.2 (for the two ends) = 3.2. I'd go 3.5 to be safe.