Safe wood preservatives

[rtmusgrove]

I want to build wooden containers for growing vegetables, how do I seal the wood to prevent rot?

[Clanad]

I'm not sure in the U.K., but here in the U.S., it's messy job to seal/preserve wood and it's not very effective unless one can pressure treat it. It's best to buy pressure treated wood... there are several varieties and many are approved for ground contact... Here's a popular product:

http://www.ufpi.com/PRODUCT/pwmicro/index.htm

It's quite reasonable and environmentally friendly...
Best of luck!

[shylock73]

You could use wood preservative and then line it thoroughly with a waterproof liner, then make drainage holes in the base and put in some gravel. I find this works very well.

[rccatnap]

Go along to your local builders' merchants (not just a DIY store) and see what they have in the way of treated wood.
The usual wood they have is 'Tanalised' which has been pressure treated already, as mentioned by Clanad.
Even tanalising doesn't make the wood last forever. In practical terms you should get 15-20 years left open to the elements.
You don't say how large you want to make the containers.
As shylock73 says, a lining would provide even more protection and don't forget those drainage holes

[shylock73]

I know it`s 2 weks since your post but I would like to add a box made of cedarwood would last for years.