There is an oak that likes wet feet, you want a deep rooted tree for hosta. There is probably a tree forum.

I have a neighbor who planted a willow in the low spot on the block to soak up all the water and it looks lovely with hosta under it....but does drink a lot of the water the hosta would like.
Linda C

i had a willow.. killed every hosta planted under it ... they will suck all moisture out of the ground .. and win any competition for such ...

try the tree forum for suggestions .... tend toward nut trees as deep rooted.. though i don't know about them with the water ...

avoid maples, poplars, willows.. and any other tree that i hate ...

i planted 6 foot bare root oaks in 2000 ... after a year of establishment.. they are growing 3 to 5 feet per year ... the biggest going on about 30 feet .... zowee that is fast.. and a good tree ... anything faster is a weak tree ...

ken

Ken,
I will look for the oaks.
Thanks to all.

I had a pin oak at my old house, and my hosta did very well under it. I even broke the rules and piled soil probably too close to the tree.

To help your clay soil, which I also had:

I got some really good topsoil that I bought from one of those "GREAT MISSOURI TOPSOIL!" ads in the paper. I mixed that with some manure, then mixed it into my clay soil. I only worked it about 6" down because it was such backbreaking work.

Then every year I put a thin layer, (maybe 1/2"), of 'super dirt' as I call it. A local nursery mixes leaf mold (why do they call it that?) and really good topsoil. The earthworms work it into the soil over time. You'd never believe that I ever had clay soil. It does take years, but the end product is amazing. Wish I coulda taken it with me when I moved!

Although hostas are very hardy and will grow in any soil, amending really helps.