try posting them in a reply

"Failure to thrive" will be the description of just about any shrub attempting to grow under any sort of large maple. It's not the hydrangeas' fault but that of the maple. They are notoriously difficult to garden under and the larger the plant the harder it gets.

I'd look at a drought tolerant and shade tolerant groundcovers....things like epimdiums, Geranium macrorrhizum, lamium. They are really your best bet for plant life under a maple :-))

Yes: changing the kind of shrub probably won't solve the fundamental issue.

Except that there can be hardiness issues with the oakleafs.

If you are open to things other than shrubs, I have had good luck with epimedium mentioned above, hellebore and martagon lily under a large old silver maple.

Shouldn't be any hardiness issues with oakleafs in zone 6.

I call up the spirit of Ego45 who had hydrangeas growing under maples. I know,. I saw them. He started out with very small plants planted in cardboard boxes filled with soil. He kept adding soil as the plants grew. The cardboard rotted eventually.

Back then I was too new a gardener to ask which hydrangea it was; but it wasn't an oakleaf. He was a very resourceful gardener. He could make nearly dead sticks from HD grow into healthy shrubs. You might be able to find his posts archived. They are worth reading

Follow up: I found a 2008 thread about planting under maples. I thought I was looking a viburnums under ego45's maple....I think they were hydrangeas given the date that we were visiting.

My rhodies do ok under maples. They started small. In addition

I have a large collection of hostas, some of which are so big they are like small shrubs. Interspersed are early spring bloomers (before the hostas leaf out) and so on. But you are looking for shrubs......