thats just it... the roots would be in a bed, would not be able to see the roots...
but I dont think fighting for water would be much of an issue...

I once saw this guy grow a plant in the center hole of a three hole cinder block....
Put cow manure on one side in an outer hole, put soil in the center, and I dont remember what he put in the other outer hole. put a seed in the center, and watered the two outer holes. Had a very nice plant as I remember..... Kind of like my local gro god... LOL