While the tree peonies finished blooming a long time ago, now it’s time for the herbaceous peonies (Paeonia spp. hybrids). The original plant that led to all of the various hybrids came from Europe and still grows there in its wild form (Paeonia officinalis).
Unlike tree peonies, herbaceous peonies die back to soil level each fall. Below the ground are fleshy roots with buds that overwinter in the soil. When the weather warms in the spring these buds sprout and the 2-4′ tall bush begins to grow. These plants have no problem with the cold and can grow into Zone 2 where winter temperatures can reach -50º to -40ºF. The southern limit of their growth is Zone 8 (10º to 20ºF). This means that peonies can be grown in all but the southernmost parts of the US.
The peonies that I remember seeing while growing up were the large double flowering plants. These are still very popular but one of the problems with them is that if you don’t support the plants, the weight of the blooms – especially after a rain – will cause them to end up on the ground. There’s nothing sadder looking than a peony in bloom with all of its flowers bent to the ground!
Because of this, when I added a peony to the garden, I chose an anemone flowering variety. These flowers are still large and showy but they’re a lot lighter and with just a little support they stay above the foliage with no problem.
As I was doing some reading about peonies, I was surprised to learn about the different kind of peony flowers and their morphology. In its natural state, a peony blossom is single with a ring or two of guard petals surrounding a circle of pollen-bearing stamens with the pistil in the center of the bloom. The tree peony in the yard has this natural structure of pistil, stamens and guard petals.
In the other varieties, the only thing that’s different about the blossom is the stamens. All the varieties you see have some rings of guard petals and a pistil in the center. But the various transformations of the stamens leads to the different varieties of peony flowers. (Two flower types I haven’t seen are Japanese and semi-double peonies – I won’t comment on their flower structure.)
The anemone flowered peony that I have growing has an amazing flower structure. It has a couple of rows of guard petals and there’s a pistil in the center of the bloom. But between the guard petals and the pistil are hundreds of petal-like structures called petalodes. These petalodes look like small petals but they’re actually transformed stamens. I’d always known that they were something other than petals but I didn’t know what they were until now!
When you get to the full double peony that we all know, here the stamen transformation is complete. What once were stamens are now true petals. They’re larger than the petalodes of an anemone peony. In some double varieties these transformed stamens that are now petals are even bigger than the guard petals of the bloom.
Whatever kind of peony you choose, they’re a pretty easy plant to grow. They need well-drained soil and sun. Dormant roots can be planted in the fall or plants growing in pots can be set out in the spring. The one thing to remember about all peonies is that they don’t take well to transplanting. A newly planted peony can take up to 3 years to get established – the peony I have has been in the ground for about 4 year and this is the first year that it’s truly full of blossoms. Peonies are also long-lived, so plant them in a spot where they can grow undisturbed and let them do their thing.
I’ve never had any insect problems on the peony but most years the plant does get powdery mildew. This fungal disease attacks the leaves of peonies but I’ve never bothered treating it. I view powdery mildew as something that just happens to some plants in the heat and humidity of August. At the end of the growing season I just clean up the dead leaves and stems of the peony to limit the number of spores that can overwinter.
Whether you like single blooms, anemone flowers or double blooms, peonies are a great choice for the perennial garden. And if you see a semi-double or Japanese peony in the garden center, give them a try as well. In my mind nothing declares that summer is almost here like a peony in bloom.