A: Peonies planted in pots are a new thought pattern for me. I did read up on them so here goes.
Peonies sometime take a couple of growing seasons to settle before they bloom, so I’m hoping that’s why yours were bloom-less this growing season. Also, they require a bit of winter chill to perform their best.
It’s the browning of the leaves that has me concerned. There is a fungal disease – botrytis – that could explain the browning. If the leaves developed brown spots in the middle of leaf which spread outward and look like a sunken spot, that sounds like the fungus. If the leaves browned from the edge inward that might be better. It could be the leaves are done for the season, might be bugs, or too much sun for this plant variety. You’ll want to give the plants a looking over to be sure there aren’t critters and treat them, if necessary.
I also think the pots need to be moved into a spot that will get morning sun and perhaps some late-afternoon sun. Peonies in this climate could live happily under the canopy of a deciduous shade tree, too, where they’d receive dappled light all growing season long. If there is a fungus among us, having the pots in the sun all day long and being regularly watered you might have inadvertently created the perfect environment for disease on a plant that would do better in a not so sunny spot.
Since the majority of the leaf is browning, it’s time to put the peonies to rest for this season. Go ahead and cut the plants down to ground level now. Pitch all of the leaf litter and stems, don’t use them for mulch or compost additive, so your chances are better to get rid of any disease or critters that might exist. As the season advances, I suggest you lay a stout 2-inch layer of bark or hay on the pots as a protective mulch layer. You want the pots to chill but not freeze hard. Planted above ground the pots are going to be far more tempted to fluctuate in temperature, so your aim is to keep them moderated. Chilled is good but frozen isn’t! You might consider placing the pots in a very cool, unheated garage or under a roofed, open patio so they’ll stay dormant but won’t freeze hard. You’ll want to remember to keep the pots barely dampened, too, all winter long. It’s damp soil that will insulate the peony roots during our dormant season, but you don’t want to keep that soil soggy wet. I use a white wood dowel in my pots as a moisture meter. Stick one in your pot down about 10 inches, leave it alone for about 10-15 minutes then withdraw it to gauge whether the soil is damp.
I’ve got my fingers crossed that your peonies will come back next year as long as you continue to take care of them. Cut them back now, cover with a protective layer of mulch soon, and consider getting them out of the bright sunny location they are in to a milder location in your gardens. It’s paramount, too, to remember to keep the pots just barely dampened enough throughout the winter months as that will be a necessary protective measure. Hope this helps, and Happy Digging In.
Need tips on growing your garden? Tracey Fitzgibbon is a certified nurseryman. Send your garden-related questions to Digging In, Rio West, P.O. Drawer J, Albuquerque, NM 87103.