The Mixed Border is a bed thirty feet wide and twenty-three deep. Big. If plants are a foot at the front, they'll need to be ten, twelve, fifteen feet at the back. Some perennials are that big and more—check out my Helianthus verticillatus.
But across the back of the bed it's just as much about shrubs and trees. Here's a variegated ash—what a beauty—that is, at least for me, so slow-growing that you can only see it if you're standing at the back of the bed.
That's the giant Siberian filipendula in back of it, i.e., completely blocking the view of the ash from the front of the bed. This has since gotten moved to the Pink Borders—the fluffy clusters of flowers aren't really the pure white you see here; there's a hint, a contamination, of pink in then was too obvious to ignore. I've just planted in its place a, fittingly, Siberian perennial aralia that's supposed to get even bigger than the usual eight or ten feet. So the ash will still need to double in size to be part of the front-the-front show.
Meanwhile, the ash's performance is no less thrilling for being, so to speak, private. Click on the pictures—and then again—to see its full intensity as well as the wider context.
I always plant Russian Giant cannas nearby; on a good Summer they get ten feet tall too. Their immense purple banana-like foliage is a vivid contrast with the comparatively tiny white-and-green leaves of the ash.
If anyone nearby is in bloom as well—like the PG hydrangea at the immediate back, with unusually large flowers, called 'The Swan'—that's swell too. But the show is powerful even if there's not a flower in sight.
Get variegated ash from Greer Gardens, who says that the tree is "A fast grower, reaching 50’ in height and about 25’ in height." How lucky for them! I'll prune mine, someday, to keep it shorter than, oh, 15 feet. At this rate I've got another five years or so before I get out the stepladder and loppers.