Tonight with the help of the brute squad, a.k.a. my husband, I dug one of the big clumps of hydrangea roots out of the back corner. I was getting eaten alive and it seemed prudent not to overdo it anyway, so I left it at that, but my brain is all fizzing with plans for this corner now, so I am chillaxing on the couch and posting.
At the very back I'm thinking I may leave the straggly remnants of the hydrangeas of insanity to grow back into bigger clumps, since they do get nice and tall. The only trick will be to keep them from flopping over on top of the stuff in front of them. The next tier can consist of rhododendron, bleeding heart, and digitalis, which all top out at 3'ish. Astilbes, azaleas, and evening primroses can go next, followed by all the shorties (trillium, forget-me-nots, periwinkle). I can also fill in some space with ferns, which I can interplant with impatiens and begonias for some nice all-season colour.
One of these days I should go on another mini-roadtrip out to Galetta Nurseries, where they're selling off all their perennials to focus on roses and shrubs. Who knows what they'll have left by this point, but I'm all about the plant sales!
Editing to also note the Peter Knippel nursery, a place way down on Bank Street which to my delight apparently stocks flowering almond, and Artistic Landscape Designs, also helpfully located on Bank Street. Hmmmm! Wonder if either of these places carry magnolia trees.