All about peonies
If your grandmother grew peonies, chances are they were Paeonia lactiflora, the typical herbaceous (dies back during winter) peony. Most of the herbaceous peonies on the market today are hybrids or cultivars of P. lactiflora.
On the one hand, these peonies are the ideal plant. They have a life expectancy of up to 80 years. They’re hardy to Zone 2 or lower. They suffer from few infestations and diseases. They’re drought tolerant, aren’t fussy about their soil and will bloom reliably in full sun to part shade. And the blooms are always a showstopper.
On the other hand, the blooms often last only a week or two, are easily destroyed by a good wind or hard rain. They are top-heavy and need tying up every year. And they go into a snit if divided or transplanted, sometimes skipping one, two or even more seasons of blooming.
There are a few things you can do to get the most out of your herbaceous peony.
Plant in fall.
Ideally, there should be ample sunlight, but some afternoon shade will provide relief if the blooms come during a hot period.
A sheltered position will help reduce damage from strong winds.
Choose your planting site carefully so you can avoid moving the plant.
The top of the root goes two inches below the soil surface. No more.
Divide rarely if at all. If you need to move the plant, though, do divide it into roots with three to five eyes each; it will come back sooner than if you transplant the whole clump.
Be patient. A new peony may take a couple of seasons to get comfortable before it will bloom, particularly if it is a young plant. Even if it does bloom young, resist cutting the blooms for the first three years.
When you cut blooms from a mature plant, take no more than half of the year’s yield and be mindful to leave as much foliage as possible.
Wait until late fall to cut back the stems and foliage and then do cut it back to about one inch above ground level. Remove any dead leaves from the area to reduce the spread of pathogens.
Tree peonies have long been the favoured form in Asia. These are woody peonies that don’t die back for the winter, which makes them less hardy. They are unreliable below Zone 6 but considered worth the risk with winter protection in Zones 4 and 5, and there are intrepid gardeners who grow them in Zone 3.
Tree peonies offer colours that herbaceous peonies do not, mostly because there are several yellow tree peonies to cross breed but only one yellow herbaceous, P. mlokosewitschii, which has only lately begun to be crossed.
Care of tree peonies is similar to care of lactifloras with one important exception: plant them deep. And, of course, don’t cut them back in the fall. Any pruning must be done right after blooming, before buds for the following year start to develop.
There is a middle ground, though, with intersectional—often called Itoh—peonies, which are a cross between woody and herbaceous. They offer some of the colours harder to find in P. lactiflora on a peony that is herbaceous and, therefore, hardy.
Intersectionals are treated just like P. lactiflora.
A very interesting peony is P. tenuifolia, often called fern-leaf peony. It’s a red single with a contrasting yellow centre and finely dissected foliage. It is smaller than other common garden peonies, not much more than a foot in height, and is well suited to rock gardens. It is very hardy, thriving down to Zone 2 or lower.