Pretty difficult conditions. I'd try Geranium maccrorhizum--Bigroot Geranium. A really tough plant. If it can't make it, I don't know what would.

Vinca minor?

I've heard Epimedium and Lilly-of-the-Valley might work but have no first hand experience with either.

Vinca/periwinkle grows anywhere--it's growing here in full sun, full shade & everything in between, under hydrangea & euonymus, on all four sides of my house--north, south, east & west. The lily-of-the-valley used to grow same as the vinca but I've been yanking that out relentlessly for years and even had one area of it removed with a backhoe. If those won't grow under your aspen tree, I can't think of anything that would. Neither drought nor wet have any effect on them that I've observed.

Solomon's seal should do okay. The variegated kind is very pretty.

Epimediums should also do okay. I find them mostly boring though except when they are in bloom, then they are charming. Maybe I don't have the right kind. Many people love them.

You'll hear multiple screams of protest about this suggestion, but under
my silver maples (with notorious root systems), I have some beautiful
stands of Aegopodium (Goutweed, Bishop's Weed). The foliage is a lovely
green-and-white, flowers in early summer resemble Queen Anne's Lace;
when it starts looking a little ratty in August, I literally mow it down, and lush
new foliage returns for the rest of the season. Yes, you DO have to keep an
eye on it because it likes to run, but mine has been growing atop that root system for 15 years now and timely editing has kept it in check.

Other successes under maples: Liriope, Gallium odoratum (Sweet Woodruff), Epimedium, Stylophrum (Celadine Poppy), Vinca, Polystichum acrostichoides
(Christmas Fern), Polygonatum. . .and in the shrub department, the "hands down" winner in my garden for beating root competition has to be Nandina !

Carl

Thanks for all the ideas! Can't believe at the speed they came in, much appreciated!

"Biokovo" geranium should do well.

Chasmanthium might work.

Keep in mind anything you plant, even if tolerant of dry soil, will need some "babying" during the establishment period.

Re: Solomon's Seal: The variegated variety doesn't seem to handle tough, dry conditions as well as the plain 'ol green variety - at least not in my yard.

Planted under my large established maple tree are hostas, Lady In Red lady fern, Japanese painted fern, variegated Solomon's Seal, Tiarella, heuchera, brunnera, and dicentra. I do water during droughts.
Jacquie

Whatever you decide to plant, you'll probably find it easier if you get very small plants and scratch the holes with one of those bent-fork things instead of trying to dig. If you encounter a large root, give up on that spot, move a few inches in another direction.

I have had good luck with Lamium galeobdolon, yellow archangel, and Japanese anemones in a similar situation. Both can be very aggressive/invasive under good garden conditions, but they behave beautifully in dry rooty shade.

A couple of native Asters will grow under these conditions - Symphyotrichum cordifolium - Blue wood aster, and S. divaricatum, White wood Aster. They both grow and bloom quite well in the dry shade under maples. Beautiful clouds of blooms in the fall.

I've read that the Gillenias will grow underneath trees with thick roots. I want to get some for myself; pretty flowers in the spring, great fall color, and best of all, they're native.

Karen

Here is a link that might be useful: Gillenia trifoliata

Skip all of the above advise, especially the vinca. If you want nice plants - shrub size - like hydrangea's, think outside of the rooting system. Get yourself a child's swimming pool. Place on top the roots of the tree or fight the tree roots with a shovel and reclaim some soil - fill the pool with soil. Drill holes in the side of the swimming pool, not the bottom - the tree will find a way through holes in the bottom. Place your plant in the pool in the dirt - it's own home with no invaders! Next frame the outside of the pool with rocks, if you don't bury the pool. This looks amazing when complete. I have both hydrangea's, astilbe and hybrid hostas growing under the shade of my silver maple - looks marvelous.