I'm now wondering if asparagus is the right thing to grow in it. Having looked at the ehow link (thanks, Cloddopper) that says if you grow asparagus in pots they need to be brought inside if the temperature drops below 64F, and not fancying trying to move a bath full of compost up the garden and into the house, I may have to rethink.
The idea of a herb garden is good but it's a long way from the house. Herbs really need to be close so you can pop out and pick a sprig or two. Hmmm, need to give this some thought.