salix nakamurana var. yezoalpina
I love this dwarf alpine willow (thanks, Ray). It's a tough groundcover willow that stays under 1' high but can get up to 8' wide. I've had it in a trough for a year and a half or so and it doesn't show any signs of world domination yet. It had a fairly modest show of catkins this spring (I'm hoping for more next year) and was a solid green texture all summer and fall, but I really like the nice yellow it has now. I'm always reluctant to buy yellow-flowering plants because it's not my favorite color. But now, on the cusp of coldness, yellow seems just right in the garden. It's the end of the season; yellow signals capitulation.