Wood protection for veg beds

AdRock

Hello, I’ve made some raised veg beds from oak sleepers and was looking for some wisdom on what to use as a wood preservative on the inside of the beds where soil would be against the sleepers.

Being oak and 10cm thick I’m hoping these will last a good 10 years or so, but was hoping to increase that lifespan with some natural oil or a liner somehow.

Any suggestions would be very helpful,  but important to mention they have to be safe for growing organic veg!

Thanks in advance 

Allotment Boy

Oak has natural oils so should last you could line them with plastic -old compost bags cut & used black side out would be ideal.

Fairygirl

Definitely line them. It's daft not to, as it also helps retain moisture. Raised beds drain more readily. 
It then doesn't matter what you finish them with. I use standard, readily available pain/stain products on mine, and although they're largely ornamental, I also grow salad crops and strawberries  in them, and always have 

AdRock

Thanks for the suggestions, I’m not keen on using any plastic materials and was thinking something like danish oil or boiled linseed oil? 

strelitzia32

Danish oil won't cut it, I think. I have mahogany kitchen surfaces, I have to get a guy in to redo the Danish oil and finish every few years. I wouldn't like to think how quick it would wear off in a raised bed outdoors! They're going to be constantly exposed to moisture so I'd line them and use a proper outdoor treatment.

BobTheGardener

Oils and preservatives will not help much if you allow wet soil to contact the wood.  I can tell you from experience that only a waterproof physical barrier will lengthen the life significantly.  I also use old compost bags as most of those can't be recycled so normally go into landfill.  If you want to avoid plastics, consider using natural rubber sheeting (you can get the stuff used for lining sandblasting booths for under £10 per square metre.)

AdRock

Good idea Bob, I’ll look into that thank you. 

I wonder if anyone knows from experience how long these oak sleepers would last for without any treatment? I’ve been using used scaffolding up to now and that’s lasted about 5 years so I’m hoping for much longer than that if I decide to leave them.

Fairygirl

I'm afraid you'll just have to be prepared to keep replacing them if you don't want to line them. 
As @philippasmith2 says - if you buy 'the filling' for them in bags, that's a better use of them than being tossed into landfill. 

KeenOnGreen

Our thick oak boards rotted in 5 years, as we lined them with weed suppressing membrane (which kept the soil away from the boards, but not the water).  They were also eaten to shreds by some sort of burrowing larvae.  As a previous poster said, only a truly waterproof solution will really make them last (and stop insects from burrowing into the wood and their larvae eating it).  We covered our raised beds at the allotment with thick black plastic, which is wrapped all the way around the wood.  We too don't like using plastic, but if it means we don't have to replace the wood for 20 years or so, then we think it's worth it.  People always think hardwood's like oak will last forever, but with constant exposure to the elements, that's sadly not the case.

AdRock

How about some sort of metal sheeting or some marine ply to line it?

Just not happy to use plastic in the garden and I always reuse compost bags for collecting leaves and weeding anyway.

Ferdinand2000

markos said:

How about some sort of metal sheeting or some marine ply to line it?

Just not happy to use plastic in the garden and I always reuse compost bags for collecting leaves and weeding anyway.

Ply contains all sorts of glue.

I tend to use offcuts of Damp Proof Membrane from other projects, so to use plastic waste rather than throw it away, after soaking in a preservative.

If you do not use plant pots, do you have a good source for non-plastic plantpots and seed trays etc? Would be interested to hear.

Cheers

F