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.

I'm the guy who paid $80 apiece for a pair of Hemerocallis 'Red Suspenders', which is a red/yellow bicolored daylily with eleven-inch flowers.
You read right: Eleven inches. (I paid $80 apiece for two of anything named 'Red Suspenders'.) So I can't be criticized as being one of those garden sophisticates for whom Flowers are a bad F-word, but Foliage and Form are good.
And good they are, filling out and brightening up the garden so flowers don't have to do all the work. Here's a dwarf Japanese maple, Acer palmatum 'Red Pygmy'.
Ferny foliage that says purple all season, and a low and starting-to-worry-me-it's-getting-so-wide habit. Fine and dandy in itself. But then with the variegated gooseneck, Lysimachia 'Geisha' pushing up at the front edges?
The yellow and green leaves are humming a jazzy but harmonious tune indeed atop the foreground of the Red Pygmy's tasteful dark ostinato of "ferny-purple-low, ferny-purple-low".
And Geisha has the typical gooseneck flowers, whose nodding soft-white cones are an echo to Red Pygmy's nodding ferny-purple-lowness. Vertical spikes of flowers would be too disruptive.
All in all, a lot going on, all of it riffing together. This plant combination has rhythm as well as harmony, self-evidence as well as second-glance subtlety. Yum!

The chrome-leaved Scotch elm is Number Ten of my favorite twenty plants: see the full line-up here.
I love this plant first and foremost because the hot-yellow leaves stay hot and yellow the entire Summer. No scorching, and (almost) no fading.
And also because the tree is so responsive to pollarding. Late in April, I cut all the branches that had grown up the Summer before...

... down to stubs.

Truly, an inch or less of I get the heavy stubs in the jaws of my loppers.

But did the elm falter, let alone fail? Not a chance: Six weeks later, the new branches are already over a foot long.

And there are several dozen of them too.
This is a tree of singular enthusiasm—or is it stubbornness? I massacre it annually, and it roars back, annually, with I'll-show-you intensity. These new growths will be eight or ten feet long by September, growing a yellow flame of foliage that's as dense as it is compact. (Unpruned, the elm could top eighty feet.) We're a good pair, my elm and me.

What the? OK, a lot going on here. That's yellow-leaved forsythia for one, posted about here. And the big-leaved bamboo is posted here. But what is the white-leaved action in the center?
Those are the young leaves of my Silver Cloud redbud tree. They unfold before their chlorophyl even starts developing, looking somewhat like the translucent seek-pod disks of the "money plant", Lunaria annua. Well, in shape if not in coloring.
Chlorophyl does creep in—otherwise the Silver Cloud couldn't grow—but the leaves remain satisfyingly "whited" the whole season. This is still a young Cloud, but it's a (small) tree eventually. So it will shade both the bamboo and the forsythia someday. Notice that there are two pairs of horizontal wires in the picture. They are the bottom rungs of a series of wires strung up to ten feet high.
I'll gently flatten my Silver Cloud to them so it will be a Silver Disk or a Silver Slab floating with tidy serenity above the wilder duke-it-out of the forsythia and the bamboo. (Yes, I can hear your exhasperation: "Louis, can't you just let something grow?" Well, yes, I could, but I worry that then my garden could be confused with yours. (Ouch.))
And also, the frame those wires are attached to had to be there anyway: It's a stabilizing end section to my Belgian fence of beeches. (I'll post about those soon not to worry. And yup, I couldn't just let the beeches "grow" either.) Further, Silver Clouds welcome some shade, and this was about the only semi-shady spot I had left. And lastly because I never heard of espaliered redbud trees, let alone an espaliered Silver Cloud redbud. So of course I had to try it.
And—right!—someday this redbud tree will live up to its name and bloom. The flowers aren't red at all, even the buds. A hot lavender actually. Check out my video here. The buds emerge all along the trunks and limbs, not just from the tips of the branchlets. So espaliering a redbud should produce a singular floral effect too.
Stay tuned.

An unprepossessing opening picture, true.
It was a glorious bright-sunny day, so the interior seems dark dark dark. These are the pair of South-facing windows in our dining room; they're unusually large for an 18th C. house. With such low sills my guess is that they're a 19th C. addition. Whatever: They are a pleasure welcoming the Winter sun as well as the Summer view. I planted all kinds of plants to make that view worthwhile. Here's the show out the lower-left sash.
Boy do I love these plants. We'll look at most of them, and soon. Right now, the gold-leaved Japanese maple.
Yup, that's the color, and all season long: Glowing gold but not over the line into "Jeez, honey, where are my sunglasses?" yellow.

It's a Japanese maple too, mind you, so has that tribe's multi-trunked classy look to the branches and trunks. So yes, it's good even in Winter, when (alas, sniff, sigh) the leaves have fallen. But if we're lucky (I haven't been so far, but I live in faith), the Fall weather is such that just the tips of the leaves turn a cherry Fall red, leaving a round interior of each leaf still gold—hence the "Full Moon" of the common name. The tree is very slow growing, so buy the biggest you can afford. After a couple of decades, it might be only 18 feet tall. It's happy in amazing amounts of shade too; conversely, it handles full sun without scorching only if the soil is rich and it doesn't have to beg for water. I never water mine even though it's on the South side of the house and gets full West sun. So I guess my soil passes the test on both counts.
More on the companion plants later—and soon.

 First, the trees get a disease that screws up their famously dense and columnar habit. In the Northeast, those poplars are scraggly and patchy, with dense twiggy areas as well as bare ones. A mess.

And then there are the famously water-hungry roots. Like (some) willows, poplars are one of the few trees that actually do "invade pipes" and clog up septic systems, wells, irrigation systems. If you need to see happy poplars, go up to Quebec, where, I'm guessing, the patchy-scraggly disease isn't hardy. (Or maybe because so few other trees are hardy up there, they grow it out of desperation.) 

For gardens South of the (Canadian) Border, poplars should be cut down, never planted. Except for this one:

Gold foliage. Gold! And that stays gold all season. The backs of the leaves are pure white too, so in a breeze the tree shimmers. 

For some reason, this poplar doesn't get the patchy-scraggly thing either.   It might still have the water-hungry roots, but mine is a good sixty feet from any well or septic system, so I say to its roots, "Truffle away!" 

Plus—so atypical for a poplar, which are normally so fast-growing they are trumpeted in those "Gets Thirty Feet Tall In Three Years" ads we all used to see in the Sunday Supplement—the gold-leaved poplars are amazingly slow-growing. Mine is eight years old, by which time a Sunday Supplement popular would be sixty feet tall.

Like many trees and shrubs with interesting foliage, gold-leaved poplars welcome severe Spring pruning (that is, after they get big enough to have anything to prune). I'm not quite ready to pollarding mine. All I've done is to clipping off the branches from the trunk below, so the tree gets the idea that it is in fact a tree, with a "clear" trunk. Even so, the poplar is already like a still photo of a gold explosion.

Gold explosion: I like that in a garden.

PS: The patchy-scraggly poplar is native to the Mediterranean.  So maybe it doesn't like the rain and humidity of the Northeast. The gold-leaved poplar is native to Canada:  it's the fancy cousin of all those happy poplars up in Quebec.  So maybe it grows so slowly here in New England because it doesn't like our sweltering Summers and (comparatively, mind you) namby-pamby Winters.

Whatever: it's a blessing to have a poplar whose roots doesn't have designs on the entire neighborhood, and whose foliage is such a shimmer from May through October.

Pink-leaved buckeye is a hasty performer. The new foliage is a startling salmon-pink.
The typical star-fish look of the foliage—just like that of its bigger, true-tree chestnut cousins—now looks like the starfishes have been parboiled to a lobster hue. It's a shock—a starfish bush.
But two or three days later, the pink shifts (alas) to bronze.

The only pink left is in the leaf-stems.
By Summer, the foliage is in full disguise of plain green.
My bush is young and spare, and (can you hear the fingers drumming on the table?) wow is it slow-growing. Someday this will be a bush with a higher profile, literally, and visible clear across the garden. Then it will command attention: We won't be able to blink.

So far I grow only one "snakebark" maple, Acer pectinatum ssp. 'Forresti', which is one of the easiest in this heat-phobic, shade-happy tribe to establish. It keeps cool because it gets morning sun only, and it repays me handsomely:
Distinctive large leaves all Summer...
And you can see the white vertical striping on the trunk that leads to that "snakebark" name.

And in Winter—oh for heavens' sake: I don't have a picture of the stems in Winter, when they turn red! (I'll shoot it this Winter I promise.) But in Spring, I get the best of both seasons: The last remnants of the Winter red, the first green—eager fresh limey—of the new leaves.
And a bit closer:

What a comprehensive display, the color of the twigs juxtaposed with the color of the new leaves. The narrow thin-ness of the twigs joining the butterfly-wing pairs of the new leaves.
In color and shape both, leaves and twigs, it's a peak-of-the-year moment.