HG: Homegrown Column December 20, 2008
Why will my peonies not bloom? Every year they grow and look healthy but will not bloom.
Here in western Colorado the problem is usually caused by one of four things.
The first is overwatering. Peonies like regular water but too much of a good thing can lead to problems, especially in our heavy clay soils. Peonies have a thick and fleshy root system which can be prone to rots if the soil is kept too consistently moist. Be sure the plants are soaked well when they are watered, but allow the soil to dry just a bit before watering again.
The next problem is that the plant is getting too much shade. Peonies need a good bit of light and if they don’t get it, the first things to suffer are the flowers. A plant can grow adequately with lower light, but it needs an extra level of light to promote blooming.
The third possibility is that the plant is old and crowded and needs to be dug up and divided.
Peonies will grow for years and years, but eventually they get overgrown and the plant loses vigor and will produce sparse flowers, if any at all. Late September to mid-October is when we recommend doing it here.
As carefully as you can, dig the entire plant up. Yes, there are still green leaves attached (and leave them alone. Don’t cut them off), but the plant will be OK. Clean the soil off the roots. I use my hands to carefully crumble most of the soil away. What you end up with is a tangled mass of those fat, fleshy roots.
There are often parts of the root system that are dead. They’re easy to spot because they’re shriveled and dried up. Cut all of that away and discard. You then want to cut the plant up into smaller pieces.
At the base of those leaves and on the top of the root will be some large egg-shaped buds.
They’re usually reddish brown in color. Cut your plant up into pieces that have at least five or six of those buds. Keeping even more is better.
Now, it’s time to replant, but before you do, take the opportunity to rework the soil by mixing in a healthy dose of compost or other organic amendment. Peonies thrive in rich soil and this will really give them a good start.
Don’t cram all of those old pieces back into the spot where the old plant was. You’re trying to give the plants room to grow and thrive. Find some new spots in the garden to spread them around, give them to friends and neighbors or just add the extras to the compost pile.
How to replant leads me to the fourth and most common problem, which is that the plant is planted too deeply in the soil.
Maybe it’s different in other parts of the country because you’ll see recommendations to plant peonies 2, 4 or even 8 inches below the soil surface. Around here, the plant often will die if planted that deep and if it does survive, it will never bloom.
I like to set those roots at a depth where the buds are underground, but barely below ground. I like the top of the bud to be right at ground level. Water them in well after they’re planted and the plants should look great for you the next spring.
Be patient. They’ll usually bloom that first spring after transplanting, but it won’t be a heavy flowering. The plant is putting a lot of its energy into re-establishing itself and growing. The following year the peonies should be beautiful.