Peonies and hydrangeas: When is a tree not a tree? (or "I've Seen Peonies from Both Sides Now...")

From the Department of Corrections Department: Many of you groaned when I tried to answer a question about tree peonies from a listener two weeks ago. In my defense, your honors, I plead ignorance about this and many other issues. I would also plead the Fifth but I have stopped drinking.

When I realized that the question was about peonies, I did not fret. After all, I had 'inherited' a beautiful pink herbaceous peony when we purchased this house circa 1985, and it has bloomed beautifully every year, despite being planted so close to the road it could tell you the license plate number of that noisy truck that just rattled the windows of our house while passing thru.

I knew the look of the flowers, and that you need to support them or those big floppy heads will droop so much that some of them hit the ground. My solution was to cut the lowest ones; some for display in a vase indoors, and some to be wrapped in damp paper and stored in the downstairs fridge until summer, when they would appear prominently in the house, leading people to believe that I might actually be good at this sort of thing. (It's an old trick a florist taught me.) And, as all herbaceous peony owners must do, I ran string across the front of the rest of the plant to support the taller flowers.

Then I became a peony expert! A new shoot had appeared next to the plant one Spring, and I just let it be. (If you could see my garden, you'd realize that leaving things be is kind of our motto: relinquatis eam solam.)

My indifference was rewarded three seasons later when a bright red peony flower with somewhat different leaves appeared on the sprout, which I later learned was technically called a 'sport'. I was now a peony breeder!

But the caller wanted to know how to plant herbaceous peonies (perennials that die back to the ground every winter) AND tree peonies (woody perennials whose above ground growth persists over winter). At that point I realized I had never actually planted a peony and wasn't sure what the deal was with the tree form. I was ALMOST sure that it was a regular old peony grafted onto a rootstock.

Luckily, I added 'but I'm not sure' (the second motto of my garden) and urged the listener to follow up on my useless advice with some research.

Which is also what I did as soon as I got home. Turns out that tree peonies aren't grafted and they're not trees; they are woody perennial SHRUBS that bloom earlier than their herbaceous cousins, bearing their flowers up to five feet in the air when fully mature. (So why are they called 'TREE peonies'? Is 'shrub' a dirty word in horticulture?)

I thought I didn't like them because of a single stalk tree hydrangea a neighbor has on display. A short window of loveliness, followed by a long period of looking like a dead tree with faded flowerheads on top. (Martha Stewart will help me solve that four-season visibility problem in a bit.)

Tree hydrangeas do not naturally have a tree form either; all hydrangeas begin life as shrubs, and only one type, Hydrangea paniculata, can be trained to a single trunk, which is done to young plants while they're still in the nursery trade. So they are not natural; they're kind of declawed hydrangeas. But they're not grafted either.

That's strike two and now I have to try and hit the ball to the right-hand side of the field. Or lean into a pitch.

Now, about Martha Stewart. I met her a few times back in the 1990's, when I was the Editor-in-Chief of ORGANIC GARDENING magazine. In fact, we were the judges at the New York City Flower Show one year. During that time, we talked about plants a lot, and I came away feeling that she was a charming and intelligent woman who had a true love of horticulture.

Now to bring it all home. While doing my research on these not-a-tree things, Google suggested I read an entry in Martha's Blog called "My blooming tree peonies", which I really liked. Instead of displaying these plants alone in the open as "specimens" Martha has hers planted in a grove formation in the understory of large mature trees, creating a flowering border whose blooms are five to seven feet in the air. (Tree peonies can tolerate shade better than their herbaceous cousins, and they bloom before those big trees can fully leaf out.)

(Yes, Martha has helpers to take care of her plants, but so do I. Like her, I do all the planning, and my tireless intern Sean does the dirty work [except with containers, where the dirt goes under MY fingernails.])

Anyway, big advantage with the tree form. Because the flowers are held up high by sturdy wood stalks, they don't flop, so you don't have to struggle to keep them off the ground. And their height makes the flowers much more visible than the ground huggers, so that visitors can better enjoy the flowers that Marco Polo reportedly described as "roses the size of cabbages".