im sorry to say it wont like being dug up every winter and submerging the pot will give you all sorts of problems with roots creeping out of the pot. it may be possible depending on your location to leave it in the ground if it is sited and protected well which can be a real polaver. if you leave it in a pot it waill want a lot of repotting and a huge pot eventually because compaired to a Dicksonia it is monsterously fast growing. great plants

Here is a link that might be useful: cold hardy treeferns

Many thanks for your response. Thats a shame, looks like I will have to just keep getting a bigger pot!

Thanks again.