How to grow peonies
Cool weather plants can even be tricked into blooming in parts of Florida with a little extra effort.
Wed, Mar 28 2012 at 4:57 PM
BRIGHT BLOOM: Peonies produce large, elegant flowers in a dazzling array of colors, from pure white to coral pink to brilliant reds. (Photo: Tom Oder)
What’s the one flower you should never leave home without?
When many people sell a house, peonies are the first plant they dig up and take with them. That’s because the peony is often as much an heirloom treasure as grandma’s china, silver and crystal.
“We have childhood memories of them from our great-great-great grandmother’s garden and carrying them at our wedding,” said Kathleen Gagan, owner of Peony’s Envy nursery and display garden in Bernardsville, N.J. “They remind us of stories and a culture we grew up with.”
Here’s a guide for how to grow peonies with the brilliantly colored and elegant flowers that will help you keep alive and enjoy your family tradition — or start a new one.
Different kinds of peonies
It’s important to know what kind of peony you are inheriting or buying in order to grow it well. There are three kinds of peonies: Herbaceous (bush), tree (tallest of the three kinds) and intersectional (Itoh), a cross between tree and herbaceous types.
Herbaceous peonies die to the ground in winter and re-emerge in spring. Tree peonies drop their leaves in winter but keep their stems. Intersectional peonies die back each winter, like the herbaceous kind, but have large flowers typical of tree peonies.
All peonies have fibrous roots and a crown with little pink “eyes,” which is where the flower forms.
Peonies need a winter chill
Where you live is critical to whether you can grow peonies and what kind you can grow.
Peonies can be grown in USDA zones 3-8 (they can also be grown in zone 9 with a little extra effort) and need a winter chill to bloom. It’s not an exact science, but a rule of thumb is that the daily low temperature in winter needs to fall below 40 F for at least six weeks, says Gagan.
For growers in Northern or Midwestern states such as Indiana, where the peony is the state flower, it’s hard for peonies to get too much cold weather.
Growers in Zone 9 as far south as Jacksonville and Tampa, on the other hand, may have to trick their peonies into thinking the plants are in a colder climate than they actually are to get them to bloom. Gagan’s tip on how to do this: Fill a 9-by-13-by-3 cake pan with water and freeze it. Remove the ice block from the pan and put it over the peony. Refill and freeze the pan. When the ice on the peony melts, replace it with another block of ice.
But I live in the South!
Another way for gardeners in warm weather states to enjoy peonies is to plant early blooming varieties, such as Festiva Maxima, Coral Charm or Rubra pleana. The problem for Southern growers in most winters, Gagan says, is not so much insufficient hours of winter cold but early arriving summer heat. The latter can cause the petals to stick together as the bud begins unfurling, preventing the flower from fully opening.
When to plant
Bare-root peonies should be planted in the spring as soon as the ground can be worked and in the fall before the ground freezes. Potted plants from a nursery will fare best if they are kept in the pot until fall and planted from September through November, after the peony has begun to go dormant.
How to plant
Because peonies are very long-lived and prefer not to be disturbed, prepare the growing area well before planting. Peonies prefer a fertile, well-aerated and well-drained soil.
Here is Gagan’s planting advice:
For herbaceous and intersectional bare-root peonies: Dig a hole one foot wide and one foot deep. Mix dirt from the hole in equal parts with compost and sand.
For tree peonies: Dig a hole two feet deep and a foot wide. For the bottom of the planting area, amend the soil at the rate of three parts compost, two parts stone dust (gypsum, available at nurseries) and one part dirt from the hole. For the area around the roots, prepare a mixture of equal parts compost, stone dust (gypsum) and dirt from the hole.
For herbaceous and intersectional peonies, here is a general guide for how far below the soil surface to position the eyes:
Zones 3-5, two inches.
Zones 6-7, one inch.
Zones 8-9, .5 inches.
Tree peonies can be planted deeper.
Because planting depth is critical to blooming peonies, avoid being too heavy-handed with compost or mulch as it adds to the depth the peony eye is below the soil surface.
Where to plant
The more sun herbaceous and intersectional peonies get, the happier they will be. Tree peonies will tolerate full sun but prefer dappled shade (morning sun, afternoon shade is ideal). Tree peonies don’t want competition for nutrients or moisture from roots of nearby shrubs or trees, so give them three-five feet of space for their roots to grow into.
Benign neglect suits peonies well. Peonies also appreciate bone meal, fish emulsion and organic fertilizers. In all cases, follow package instructions. If you must use a chemical fertilizer, consider 5-5-5 or 10-10-10, again following label directions.
To help plants get established, give them a weekly soaking in periods when there is no rain. Peonies don’t like wet feet. Water pooling around the plant is a sign of insufficient drainage or over-watering.
Flowers of all peonies are showy, often fragrant and range from a display of simple single petals to complex layers of petals. They come in a dazzling array of colors, from pure white to coral pink to brilliant reds
Peonies are stunning in a mixed border. Gagan says they are especially effective when planted among bearded iris.
My peony won’t bloom
There are three main reasons a peony won’t bloom:
Insufficient sunlight. Peonies need at least five hours of sunlight to bloom.
It’s too young. Peonies take three years to bloom.
It’s planted too deep. This is the most common mistake. Remember, mulch lightly.
Got more advice for how to grow peonies? Leave us a note in the comments below.