Winterizing Exposed Potted Perennials
Sometimes, you might not only need to leave your perennials in pots outdoors all winter, you might also need to leave them right out in the open in a windy, exposed location outdoors all winter. Relax. You got this. Because winterizing exposed potted perennials is a piece of cake. Keep it right here to see what I mean.
Table of Contents
Introduction to Winterizing Exposed Potted Perennials
Greetings from hardiness zone 5B/6A, readers and subscribers. Today’s article is going to definitely be of some use to you if you’ve got any perennials in pots sitting in exposed locations outdoors that you need to protect from the cold, but you’re not sure how to go about doing it. Regular readers and long-time subscribers might remember my article of a few years ago, “How to Overwinter Potted Perennials Outdoors.” In it I described a really simple way to keep potted perennials safe all winter by essentially placing them in a sheltered location, building a “bunker” of fallen leaves around their pots, and mulching them in. Easy and effective.
You might find, however, that some of your perennials that will be spending all winter outdoors are not – and either will not be or cannot be – placed in a sheltered location. For example, it could be that the pots are either too heavy to move, or have attached climbing structures that make moving them to a sheltered spot impossible. Well, winterizing exposed potted perennials is not a tough nut to crack. Below, you’ll find the simple steps that I use in my own garden to winterize my potted plants that brave the winter months out in the open, and you’ll also learn a simple rule of thumb that I use to help me decide whether or not I need to do any winterizing at all. After you check out my six step plan, as well as the way to determine whether or not you even need to use it, have a look at a few product recs that can help make the job of winterizing exposed potted perennials even easier, and deliver you and your potted plants some awesome winter survival/spring renewal results.
6 Simple Steps to Winterizing Exposed Potted Perennials
My six step plan for winterizing exposed potted perennials is a snap to follow, and it’s effective for any number of cold-hardy perennials. For you, moving forward with this plan, of course, requires some basic knowledge of the plants you’ll be winterizing. For example, some really important things to know about each of the plants you’ll be winterizing are its specific pruning requirements, feeding requirements, and hardiness zone. This information will directly inform how and to what degree you implement each of the six steps.
Step 1: Prune (if necessary)
Some plants do great after a winter pruning, some absolutely need a winter pruning, and some, which flower on the previous year’s growth, should be pruned only minimally, or not at all. Know which plants need pruning (and how much pruning they need), and bust out your pruning blades. It’s that simple, sports fans. Chop-chop!
Step 2: Fertilize (Some You Will, Some You Won't)
Once again, some plants do well with a very late season feeding. I’ve got several perennials that overwinter outdoors that appreciate a late autumn feeding. When I fertilize these, I feed them approximately half of the amount of their regular season portions. The particular fertilizer I use, which you’ll find in the product recs below, is particularly effective as a cold weather supplement. It’s got a healthy population of beneficial microbes (some of which remain at least somewhat active at various times throughout the late fall, winter, and early spring, depending on the frigidity of the temps) that assist the plant in handling cold, and contribute to its effective assimilation of the product’s nutritional components. Breakfast of champions, I’m tellin’ ya.
Know your plants’ feeding predilections. If some do well with a very late season feeding, part of your winterizing exposed potted perennials plan should include fertilizing.
Step 3: Burlap the Dirt
Burlap is amazing stuff. It’s made from fibers of the jute plant and it works wonders as both an insulating product for plants, and a great means of underlaying any mulch that’s applied around the bases of those plants and that will be removed once the coldest months of the year have passed. This last part is what we’re talking about here in Step 3. Since we’re ultimately going to be applying a thick cover of mulch, or some other natural insulating medium (fallen autumn leaves, for example), on top of the dirt in our exposed potted perennials’ pots, laying burlap down over the soil before adding the mulch, etc. will make removal of said mulch in the springtime super easy.
Burlap is perfect for this application because it acts as an insulating medium in its own right, and its “netted” structure allows moisture/precipitation to easily penetrate down to the soil in each plant’s pot, and ultimately to the plant’s root system.
Step 4: Burlap the Stems (if necessary)
Some plants overwinter successfully only if their aerial structures (aboveground parts like trunks, stems/canes, branches) are insulated from the cold. My hardy banana (Musa basjoo) is one example of a plant whose main stem needs that extra level of insulation. Burlap is a great material with which to either wrap a particular plant’s individual main stem or trunk (as in the case of my banana), or enshroud the whole plant – trunks, main stems, branches, and all. Burlap sacks are usually perfect for covering the whole plant. Again, burlap is great for this because it also allows for the penetration of moisture. Another great insulating product, as you’ll soon read below, is bubble wrap. I know a number of incredibly accomplished master gardeners who use bubble wrap to enshroud not only all of the aerial structures of their potted plants during the winter, but the pots in which those plants are growing, too. It’s also a brilliant methodology. For the aerial structures of my own overwintering plants, I’m more of a burlap kind of guy, but again, you’ll soon see that bubble wrap does figure big in my methodology for winterizing exposed potted perennials.
Step 5: Insulate the Pots by Wrapping Them with the Good Stuff
And the good stuff is… bubble wrap! Here’s the deal: I plant all of my potted perennials in either plastic or resin containers. I do this because the sometimes extreme temperature fluctuations over the course of a year here in my Michiana Shores 5B/6A garden can result in contraction/expansion of not only the soil in each pot, but also of the material of which the pot is made. Clay or terra cotta pots can crack if they’re left out in the elements season after season, year after year. Since plastics and resins easily accommodate the temperature variations due to their intrinsic flexibility, I opt for pots fabricated from these materials. The downside to this choice in container materials is their comparatively poor insulating capability. Plastic gets cold in the winter and allows that cold to penetrate to the soil inside a given container, and to the roots of the plant growing in that soil…
So, I’ve gotta insulate my pots. And for this, I use bubble wrap. Bubble wrap works great for a number of reasons. It’s super easy to apply, it has sick insulating capabilities due to the thousands and thousands of air pockets that comprise its structure, and its clear plastic bubbles act as miniature “greenhouses,” trapping the warmth of sunlight within their tiny plastic chambers. The thicker the bubble wrap layers that are applied around a particular pot, the better the insulating qualities of the product. I typically insulate my plants’ pots to a thickness of somewhere between 1″ and 1-1/2″ of bubble wrap. I use plastic packing tape to secure it. The whole system works like a charm.
Note: Another method available in the winterizing exposed potted perennials paradigm for insulating a given plant’s container involves simply lugging a bunch of bags of mulch, soil, etc. out to the pot’s location and essentially building a “bunker” that encircles the pot. Using bubble wrap to accomplish the same thing, however, I think is cheaper and easier.
Step 6: Mulch
This is a critical step, and it’s also the last step (unless you decide to sprinkle some cayenne pepper or other pest deterrent all over the whole works to keep little digging critters out of your pots). Wood chip mulch, or other organic media, provides incredible insulating properties while allowing moisture access to the soil in the pots and to the roots of the plants growing there. My two final step insulating media choices are wood chip mulch and fallen leaves. In terms of selecting one of these two media for insulating a particular plant, I look to that plant’s cold weather survivability. In my garden, my hardy banana requires the most stringent cold weather protection. For it, I use wood chip mulch. This material allows for really thick layering without the potential for thickness loss from wind. I can pile on a super thick layer of wood chip mulch and not worry about the wind blowing all of it off the pot.
For plants like my potted climbing rose and my potted flowering quince bush, a thick layer of fallen autumn leaves is easy to cram down into the pots and mass up around the plants’ main stems and canes. Like wood chip mulch, a reasonable layer of leaves also allows for moisture penetration down into the soil in each pot.
In either case, whether it’s wood chip mulch or fallen leaves, the insulating layer provided is critical in protecting a particular potted plant’s stem bases and root crowns from frigid winter temperatures.
Note: If your potted plants are hassled by burrowing or digging rodents like chipmunks or squirrels, feel free to add a generous sprinkling burrowing animal repellent or ground cayenne pepper directly to the soil in your pots, to the burlap layer you’ve placed over the soil, and/or to the mulch (or leaves). This is a practical insurance policy to buy into when winterizing exposed potted perennials in digging rodent territory.
Some Exposed Potted Perennials Don't Need Winterizing: Know Your Zone (and Theirs)
As far as winterizing exposed potted perennials as a methodology is concerned, sometimes the point is moot. Simply put, there are certain extremely cold-hardy perennials that need no winterizing whatsoever. I’ve got a few of those growing in my own garden. “But how do you know when a plant is cold-hardy enough to not need any winterizing protection?” you ask. Read on to check out the rule of thumb that I use in order to make that determination. Hint: You really need to know your own hardiness zone, and the hardiness zones in which each plant in question can survive.
The "You Don't Need to Do Anything" Rule of Thumb
My rule of thumb for not taking any winterizing steps for my potted perennials is as follows: if the plant is hardy to at least 2 full zones lower than my own hardiness zone, I definitely don’t need to worry about winterizing it. If the plant is hardy to 1-2 full hardiness zones lower than my own hardiness zone, I probably don’t need to winterize it, but I still do. If the plant is hardy to within 1 hardiness zone of my own zone, I definitely winterize it. Let me give you a couple of examples. My hardiness zone, though I typically consider it 5B/6A, since it sometimes dips below -10° Fahrenheit in winter, it typically doesn’t. Generally, the coldest it gets is between -5° and -10° Fahrenheit. So if I had to really narrow it down, I’m probably gardening in zone 6A. That being said, I have two potted horseradish plants that I grow as ornamental perennials. These plants are hardy all the way down to zone 3. This is three full zones colder than my own zone. These plants need no winterizing whatsoever. I also grow a large Russian sage plant in a pot in my garden, which is hardy down to zone 4. Once again, because it is hardy at temperatures in two full zones below mine, it needs no winterizing protection. I grow a flowering quince bush in a massive, exposed pot in my garden. This bush is hardy down to zone 5. Since this is at or within one full zone of my own, I definitely winterize the hell out of it. Would it survive without winterization? Probably. But I’m not taking any chances.
3 Great Product Recs to Aid and Abet You in Your Own Winterizing Exposed Potted Perennials Efforts
You want to be successfully winterizing exposed potted perennials in your garden, do you? Well then, you gotta have the goods. These will definitely help.
American Bubble Boy Bubble Boy 700′ Total Length 4-roll Pack. There are some huge advantages to protecting exposed potted perennials outdoors with bubble wrap. Cost effectiveness, excellent insulating qualities, and ease of use are just a few that come to mind. This particular product makes bubble wrapping even easier. The 4-pack comes with a total of 700 linear feet of small-bubble, 3/16″ thickness product that’s perforated every 12″. You don’t even need scissors to wrap your plants and their pots. Easy peasy, guys and gals, and very effective. Learn more, or order this product here, directly from Amazon, by clicking the #advertisement link.
American Bubble Boy Bubble Wrap 700′ Total Length 4-roll Pack
Click here to learn more or to order
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Espoma Organic Plant-tone. I am a huge fan of Espoma’s line of organic fertilizers. Plant-tone is the one I use for the majority of the plants in my garden. It’s got an N-P-K ratio of 5-3-3 and is a great all-purpose organic fertilizer. It works perfectly for an incredibly wide variety of ornamental plants. Again, Espoma Organic Plant-tone is the food that a huge number of my plants get. They love it, and it shows. You can learn more, or you can order this product here, directly from Amazon, by clicking the #advertisement link.
Fiskars SoftGrip Bypass Pruner. If I had to pick one pruner – and only one – to use for the duration of my gardening days, this would be the one. My own pair has performed beautifully year after year, and has remained as sharp as a razor. It’s got a 5/8″ cutting gape, and amazing leverage, power, and precision. Like I said, if I could pick only one pruner, this’d be it. Click the #advertisement link to learn more, or to order it here, directly from Amazon.
The Winterizing Exposed Potted Perennials Wrap-up
Alrighty, guys and gals, you know what to do now. You’ve got my simple 6-step plan for winterizing your own exposed potted perennials, and you’ve got my highly sophisticated, mathematically derived rule of thumb for knowing when you don’t need to winterize a particular plant, and you’ve got some extremely solid product recs (all products I use and heartily endorse). So gang, there’s not much more for me to tell you other than “You got this, boys and girls, so start winterizing!!!”
And one more thing, gang: have a watch of this RGG YouTube Channel short for a fast (it’s 58 seconds in length) look-see of the winterizing exposed potted perennials process and finished look in my own garden. Click here to watch the vid.
Thanks for sticking this one out to the end, my dear readers and subscribers. As always, your kind interest and your readership are dearly appreciated.
Cheers, and Happy Gardening!
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Excellent advice. Information detailed in easily understandable terminology.
Thank you, Rick, for having a read of the article. I’m happy that you enjoyed it and that it was comprehensible. And, of course, thank you for your kind thoughts. It’s all truly appreciated.