Water

 

Water

When you look at a hosta, it's obvious this is a plant that needs lots of water: a large, rather thin leaf, like most hostas have, will evaporate a lot more water than a small, thick leaf.  This evaporation must be compensated by a high intake of water.

Looking at the natural habitat from which hosta originate, this theoretical reasoning turns out to be correct: the arias in Korea, China and Japan where hostas come from have an average rainfall that is way higher than that in Europe and the United States (with the exception of the northwest).