They are made from Larch, which is naturally tough so doesn't need treating.
This installation was for a balcony in an office in Southampton, specifically a balcony off the canteen. So the client wanted planters full of mixed herbs that the chef could use in the kitchen. Job done!
I showed these to my partner with some trepidation as I feared that she would like them so much that she would want one on our terrace at home. So far I have got away with it!