Peonies perfect for Prairies

Hey there, time traveller!
This article was published 16/12/2023 (655 days ago), so information in it may no longer be current.

Warmer winters and hotter summers are compelling gardeners to look at ways to create more resilient landscapes. Is there a gardener right now who isn’t wondering about the cumulative effects of the successive freeze-thaw cycles we are experiencing? In the absence of a decent snowpack, frequent freeze-thaw cycles cause the soil to expand and contract with the potential for injury to the root systems of plants, especially those that are shallow-rooted.

It’s time to take a closer look at the merits of woody peonies, says Myra Froc, president of the Prairie Peony Society. Froc lives in the Qu’Appelle Valley north of Regina. She and her husband Gene grow over 700 peonies on two acres including 550 herbaceous peonies, 85 Itoh peonies and about 120 woody peonies.

Woody peonies are woody-stemmed flowering shrubs that can re-bloom on old stems. It’s incorrect to refer to woody peonies as tree peonies, says Froc, but that seems to be the name that sticks. “Woody peonies have huge root systems that eventually reach deep into the soil,” she says. “They are probably one of the easiest plants to grow and are very adaptable to different light conditions, clay soils, in addition to being very cold-hardy and drought-resistant. The fact is, woody peonies would be a very good plant for anyone who is just beginning to garden or starting to grow peonies.”

Froc is very interested in the subject of peony gardening in this time of climate change. “Even mature herbaceous peonies can go two or more weeks without watering in extreme heat approaching 40 C,” she says, “but the Rockii woody hybrids can go a month or more without any kind of moisture.”

The three main groups of woody peonies are Rockii hybrids and distantly Rockii-influenced; Japanese, Chinese, European and American Suffruticosas; as well as Lutea hybrids and species woody peonies. The Rockii hybrids and Rockii-influenced hybrids are the most winter-hardy and heat-tolerant. (Rockii is pronounced “rocky-eye.”) “Woody lutea hybrids do quite well in the Prairie climate,” says Froc, “but need more adequate winter protection than most Japanese suffruticosas seem to need. Suffruticosas have different degrees of tolerance to heat and cold.”

The Rockii hybrids grow anywhere, she says, and are the first to bloom, sometimes as early as the last week in May, but typically in the first week of June. “They are very floriferous and can withstand extreme temperatures,” Froc says. Froc grows several different types of woody peonies for a bloom period that extends seven to eight weeks. Woody peonies have large, dramatic flowers with dark basal flares. There are cultivars with single blossoms or double blossoms.

The overall size of woody peonies can be substantial. “Rockii’s grow very big,” says Froc. “Rock’s Variety grows to about five feet (1.52 metres) tall and is a little wider than it is tall.”

Despite the hot, dry conditions over the last two summers, her woody peonies bloomed profusely. “They have enormous root systems,” says Froc. “The roots of Rockii peonies can go out as far as eight feet (2.4 metres) from the crown of the plant. Rockii peonies originate in Gansu province and the central plains of China which have a continental, semi-arid and cold winter climate similar to ours. I think ours is a little harsher in some respects, but Rockii peonies are so adaptable to most soil types and climate anomalies. When there is a late frost, they just shake it off and thrive quite well.”

Unlike herbaceous and Itoh (intersectional) peonies, woody peonies are not cut back in the fall. “We get such fluctuating temperatures here in the Qu’Appelle Valley in the winter along with a lot of wind,” says Froc, “but Rockii peonies seldom have any dead wood that needs to be pruned unless really strong winds cause breakage to their branches. Otherwise, they tolerate wind quite well.”

Rockii peonies tend to retain their leaves right into November, says Froc. “They have brilliant fall displays — red, orange and yellow leaves. I like to defoliate mine because some of them don’t drop their leaves. It’s good to remove the old leaves because diseases can occur in spring when rainfall splashes debris on the ground and spores come alive.”

A distinct advantage of Rockii woody peonies, says Froc, is their ability to grow in full sun or half sun. “There doesn’t seem to be any difference in growth although the sheltered ones keep their flowers longer in hot temperatures,” she says. Froc has observed the impact of El Niño winters over the years. “Younger trees and even some of our native Prairie trees suffer when there are frequent freeze-thaw cycles. Fortunately, Rockii peonies seem to tolerate freeze-thaw cycles better than other plants,” she says.

Froc is keenly interested in mitigations for all types of peonies and experiments with many different methods. Foremost, it is essential to establish young woody peonies as well as possible by watering regularly. Froc covers all her peonies for winter with styrofoam boxes which she then covers with insulated construction tarps.

“The main purpose is to protect them from extreme cold temperatures but also from the effects of repeated freeze-thaw cycles and desiccation of the stems.”

Froc predicts that in five years the Prairies will see the same hot temperatures Kansas typically experiences. “We are going to have to grow plants that can adapt to all these changing conditions,” she says. It takes a long time to develop a woody peony. There are numerous woody peony cultivars to choose from but too few retail vendors.

Rockii woody hybridized peonies such as Rock’s Variety cost much less than many Itoh peonies. “You can purchase a Rock’s Variety for $50 or $60, or even $40,” says Froc. Of course, it depends on where they are coming from. In Canada, Rockii hybrids are available through Halifax Perennials in Nova Scotia and Les Jardins Osiris in Quebec. It’s important to look for Rockii hybrids that are three-year-old grafts or older, says Froc, as these will be better suited for survival in the Prairie climate. Unfortunately, some outlets sell mostly one-year grafts or do not indicate how old the grafts are and whether they are grafted onto non-adventitious lactiflora roots. Solaris Farms in Wisconsin is an excellent source for quality plants, says Froc.

If some of this is starting to sound too complicated, consider the advantage the Prairie Peony Society offers. Members have the opportunity to learn about all the different types of peonies, but they can also take advantage of group orders and annual root sales. Members also have access to garden tours, a quarterly newsletter, an annual peony show and educational webinars. In January, the Prairie Peony Society will host Hazel and Joe Cook, owners of Blossom Hill Gardens in Ontario, for a presentation on how to prepare, select, groom and present peonies. Webinars are also planned for February and March. To inquire about membership, email Myra Froc at mfroc@sasktel.net.

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