Wave Hill is such a bounty of great design as well as plants, and more bountiful still because so many of the plants are so established, so mature, so settled in. For someone who is "just" now creating his lifetime's garden (OK, 14 years and counting), seeing how impressive my often-small often-young plants can become is heartening—no thrilling—indeed.
Here's Paeonia lutea, literally Yellow Peony, living up to its name.
It's a "tree" peony, a shrub, not a perennial. And unlike the perennial peonies...
...yellow is a common color in tree peony flowers. And these flowers sure are small, too, at least for a peony. Flowers that are common and small: what's to love? The sensational foliage.
The leaves are large, even a bit tropical and palm-frondy, and point energetically upward. Remember also that tree peony flowers—nash, damn, dag-nabbit—are twice or thrice as short-lived as perennial peony flowers. A couple of days, a week tops, for the entire show, and then you're looking a just leaves for the rest of the season. (And yes, just sticks for the entire winter.)
A tree peony with fantastic foliage, then, is a garden godsend.
This bush wasn't labelled (as far as I could see, that is, without getting on my knees and, gulp, looking shamelessly up its skirts), so I'm thinking it's "just" Paeonia lutea, not the even-more-ferny-leaved cultivar I have, Paeonia lutea 'Ludlowii'.
But with these leaves, and on this impressively-sized bush, this tree peony should be on everyone's must-have list.

Peony flowers are—even to me, a serious foliage freak—a gift from the gods. But some peonies that still do flower are even more engaging on account of their leaves. Paeonia lutea 'Ludlowii' is at the top of the list. This is a tree peony, with woody stems that live year-to-year, and a large shrubby habit. Ludlow's can get six feet tall and wide, and more. But even if it were a dwarf, or even if it only got three leaves a season not (on old plants) a hundred or two, this would still be a peony to lust over, a peony to crave, a peony that you must-have.
Here's an adolescent bush at a client's garden, probably six feet wide and almost five tall.
As you'll see from a post in early May, the leaves are large and quite ferny, giving you that lacy-foliage look but much larger than any hardy fern could provide. (Peonies are one of those blessed rare tribes that do better with cold winters and cool summers. Eat your heart out North Carolina.)
Mine is but a pip, with only a handful of short canes that will produce, oh, ten or twelve leaves this entire season.
Just you wait and see how thrilling those leaves are.