I am building two large organic vegetable box gardens - 16 by 4 ft. and about 3 ft deep. I was wondering about how concerned I should be about slowing the wood rotting over time. I am using redwood. I was thinking of lining the interior with plastic, but I don't want it to leach anything toxic into the soil. Do I need to be consider a lining, and if so, is there a kind of plastic that is recommended?
I have gone through the same considerations that you are doing. I decided to stick with inexpensive and untreated wood on the basis that it will take a few years to fall apart anyway. It is very likely that I will be changing my garden plans at least every two years, so that doesn't matter to me. I don't want a garden box that will outlast my use for it, and be unnecessarily expensive.
Mine is made of some clean lumber, of several species, that was left over from a Rotary Club picnic shelter project. There are three 12 foot x 3 foot boxes, 24 inches deep, surrounded by chicken wire (I have a lot of yard bunnies).
I expect the wood to show weathering and rot after the second season, and then become wood for the bonfire.
Greg
You may want to check the soil pH over time because redwood has oxalic acid in it and it will lower the pH. Nothing that ashes can't fix. Don't sweat the oxalic. It's put in bread to keep it from spoiling.
- Bill Cloribus gustibus non disputatum (mostly)
I'd probably line it with 3 mil polyethylene - the kind you can buy as a drop cloth. A few years ago, I converted a broken down redwood picnic table to a garden box. It lasted about 4 years with no liner. Sorry I did not line it. Now I just use 20 inch plastic pots. Offhand, I cannot think of any plastics, with exception of rubber, that might leach toxic materials.
What's your time scale? I made a raised bed and greenhouse planters out of 2x12 rough con heart redwood twelve years ago. There has been some rotting, but the beds should be good for at least another five years. Maybe ten.
I have built raised gardens from composite decking material, cedar decking planks and finally cypress without any sort of lining. Don't have any that are more than a year old so no history at this point but seems like any of these would be OK for the long run. I was able to relocate a composite garden quite easily by merely taking a shovel and prying it up all around and moving it intact to another location. The soil that remained was raked out into the surrounding lawn. Jay raised-garden-bed.com
I use leftover wood from construction sites. Even common douglas fir will last for a few years. I have a couple of planters 5-6 years old with no problems yet. A little rotting in some places. (Dry sunny socal ) When it is too decomposed to hold itself together, break it up and burn the big pieces.
stonerfish
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