Winter Proof Your Peonies
We can all agree that the spring of 2021 has been rough at best. It seems most of the United States (and much of the northern hemisphere) was absolutely abused by the weather patterns, storms, and temperatures our temperamental winter felt necessary to throw our direction in a spiteful fit of jealous rage when learning we were eager for it to end and spring to arrive.
With that preface, I think you may understand why I wrote about winter-proofing your beloved peonies in the middle of April. There was little escape from this poor spring in my neck of the wood of Alaska; March saw over a foot of extra snow, cold winds, and below-average temperatures that carried well into April (if March comes in like a lion and out like. lamb, then count me out of the shepherding business). Not only did our wintering peonies have to endure the brutality of the Alaskan winter, but they are now forced to weather out an equally brutal spring. But they don't have to go at it alone; there is a simple technique that most commercial farmers use to winter-proof their peonies to help see them through the leaner months of winter and potentially protect them from the rare temperamental spring.
Is It Necessary?
You may know these luscious and vibrant perennials are some of the hardiest flowers around; cold-resident, drought-resident, moisture-tolerant, pest-proof, disease-hardy, and you would be right to think so — it's the reason they're such a popular cash crop in Alaska, to begin with. They thrive in cold climates with many varieties easily adapted for temperatures at the USDA cold-hardiness zone 2 (50º below zero F, or 45.6º below zero C). In fact, the NDSU reports peonies require 500-1,000 of winter chilling hours at temperatures between 32-40º F (0-4.4º C) or colder to thrive. This could easily make peonies the kings of the north where flowers are concerned, so why bother blanketing the king from his own element?
Consider these two reasons:
Peonies are expensive! Bulbs alone can average five dollars a root, with some exceeding thirty dollars per plant. The last thing you want to risk is potential die-off or sickness in the plant you paid so much to enjoy.
Tolerance is not ideal. Yes, your peonies can survive bitterly cold weather and brutally rough winters, but that does not mean they will enjoy it. Your peonies can survive terrible winters, but you don't want them to just survive; you want them to thrive. A sickly and weak plant popping up every spring to disappoint you with low vigor and minimal flowers is not ideal; you want a thriving plant that gets better with time, not worse. To achieve this, you must offer your peonies a leg up.
Row Covers
With that lengthy intro out of the way, let's see what we can do to winter-proof your peonies. It's simple; row covers. Every year, when autumn transitions to winter, I apply a thick layer of row cover material to keep my peonies safe and comfy through the bitter months. This achieves two objectives:
Foremost, it creates a buffer zone between the cold air and soil and slows the chill transfer between them. This insulates the roots from the cold, effectively keeping the soil (and thus roots) warmer and away from the brunt of the cold.
It prevents ice build-up in and around the roots that could potentially damage the more tender tissues of your flowers.
This simple technique is cost-effective and easily applied, taking no more than a day to achieve (or less for garden-only growers).
Recommended Cover Materials
The row-cover types are essential here; I use a single cover material, and though several are available, I only recommend a handful.
Straw. I use this: a generous heap of clean, dry straw applied snugly over and around the soil in direct contact with your peonies. Although there are various straw materials, and I would say they're equally effective — ensure the straw you apply is dry and clean with no apparent signs of mold, mildew, or other fungal or bacterial growths.
Burlap or winter fabrics. Though I don't personally use this, burlap and winter fabrics are another excellent winter cover. Be warned, layering may be necessary in extremely harsh climates and yearly sanitizing is recommended to prevent the transfer and spread of disease and pests. Burlap can be used in tandem with straw covers for a maximized effect.
Materials to Avoid
Now, there are plenty more I DO NOT recommend at all, such as:
Garden mulch. Don't use the wood chip, bark, or peat mulches used in garden weed suppression. These hold in moisture and harbor diseases. They also have little insulating capacity and will do nothing but reduce the chances of your peony's survival.
Leaf litter. For the same reasons above, do not use leaf litter. Yes, it has a greater insulating capacity than mulches, but it will retain moisture and potentially harbor diseases.
Sawdust. Sawdust will leach nutrients and minerals from the soil. It also retains moisture and will lead to ice and rot.
Wood-chips. Again, wood chips absorb and carry far too much moisture. Chips of cedar and pine woods are disease and pest resident, but they will (like sawdust) leach nutrients from the soil, particularly nitrogen and phosphorus.
When and Where to Use Row Covers
Now, straw or fabrics are suitable for winter protection when necessary or recommended. There are climates and conditions where I do and do not recommend using winter covers for peonies. Consider these recommendations to see where your location and climate fall:
Recommended uses of winter covers
Areas of cold, dry winters. If your winters regularly drop below 20ºF (-6ºC) with little to no precipitation, a winter cover can prevent cold damage to your peonies.
Areas of cold, snowy winters. If your winters regularly drop below 20ºF (-6ºC) with moderate to high snowfall but little to no rain, you can employ winter covers for your peonies.
Where not to use winter covers.
Areas of warm winters. If your winters regularly stay above 20ºF (-6ºC) with little precipitation, relax; winter covers are unnecessary. Your peonies will do just fine as is.
Areas of wet winters. If your winters regularly stay above 20ºF (-6ºC) with high amounts of wet precipitation such as rain, sleet, or ice, it's best you leave your peonies as is; covers, even dry ones, will absorb and hold much of that moisture in and under them. This encourages standing water and heavily saturated soils, which can lead to root rot.
Conclusion
It may seem like a lot, but giving your peonies every chance to thrive and be more robust, healthy, cared-for plants is the least we can do as growers. If so needed, winter-proofing your peonies will ensure they continue doing just that for decades. Come on; they give us so much through the growing season; what's a little warmth through the winter in comparison?