9 Clever Ways to Insulate Your Potted Plants in Cold Weather
Our container garden specimens are often too valuable to sacrifice to winter extremes. To get creative on preserving your favorites, employ crafty measures of insulated overwintering. Streamlined techniques using household and natural materials offer winter protection and may even promote an earlier spring reemergence. Gardening expert Katherine Rowe explores ways to enhance insulation for overwintering success.
Contents
Container gardening fits various scales and situations, from small-space gardening to accessible opportunities to adding architectural styling and planting designs. It allows us to feature specimens as focal points or create limitless arrangements for color, texture, fragrance, and culinary delight.
Parting with these beloved arrangements come winter can be too difficult, especially when there are years of life left in a plant. For lasting arrangements, proper overwintering is important for the best chance of success in preserving the selections.
From perennials to shrubs to trees, simple, creative insulating techniques offer protection against winter extremes. These aren’t foolproof, especially in variable conditions and frigid climates, but they’re worth a try to give your favorites the best foundation to endure cold weather.
Overwintering Basics
In overwintering, the primary goal is to protect the roots and crown from extreme temperatures, frost, winds, and winter sun. Roots are more susceptible to damage in a container than those in the ground.
Container plants lack the benefit of surrounding soil mass, which provides insulation. Because of their above-ground siting, only a thin wall protects roots from surrounding air temperatures. The soil is susceptible to frost heaving, leading to root disturbance and damage.
In mild climates, insulation may involve a thermal blanket or burlap cover during cold snaps and windy spells. In colder climates, more protection is necessary to ward off damage.
Tips for overwintering potted plants:
- Prepare tropicals and annuals before your first fall frost date and tender, borderline hardy selections shortly after.
- Wood, metal, plastic, and glazed pots are less susceptible to cracking than porous clays and terracotta. Provide extra protection, like a wrap, for porous materials.
- Larger containers with more soil mass overwinter better than small ones.
- Water through frost. Then, check moisture every few weeks and water occasionally if overwintering undercover.
- Overwintered growers may break dormancy earlier than their outdoor counterparts. Harden them off for spring by gradually removing winter protection.
Enjoy Them Indoors
Warm up the interior-scape by moving tropicals, herbs, and select annuals indoors before the first frost. Hanging baskets and pots expand the houseplant jungle. Depending on the specimen’s requirements, they’ll need bright, indirect light or a sunny spot near a window.
Keep them out of heating and cooling drafts and away from fireplaces. Growth may naturally slow as seasonal conditions change, but it will resume in spring.
Tender perennials, shrubs, and trees can take shelter in an unheated space like a garage, basement, shed, or cold frame. An enclosed space offers the best protection against winter elements and the best chance of survival.
The ideal indoor temperature range is between 30-40°F (-1-4°C). The overwintering visitors benefit from a little natural light in these spaces, so windows or skylights are ideal. Without natural moisture from rain or snow, they require occasional watering so roots don’t dry out completely. Once a month is usually sufficient.
Dig In
If you have the space, consider digging a hole for the container to ride out the season outside. Dig a large enough hole to house the entire pot, and situate it so the rim is just above the soil line. Return the surrounding soil to bury the pot.
This technique mimics in-ground planting and provides the warming soil mass that above-ground containers lack. Add a generous layer of mulch around the top of the pot for added protection.
Nestle In Groups
If you have a number of containers, cluster and huddle them together for insulation. Place the most tender selections and/or smaller pots in the group’s center. Surround them with the hardier specimens and larger containers.
Group them against the wall of a building, structure, or evergreen hedge for protection from winter winds and extreme temperatures. Insulate with mulch like shredded bark, woodchips, straw, or leaves.
Wrap Them Up
Whether nestled together or standing as single-potted specimens, an insulating wrap protects the roots. During extreme cold snaps, wrap both the containers and exposed plant parts in frost cloth, fleece, thermal, or frost blankets. Top singular plants with a frost-cloth cover, cloche, or recyclable bottle or milk jug for an easy off-an-on topper.
Some gardeners wrap their pots in layers of plastic bubble wrap (at least three layers thick), insulating foam, or burlap secured with plastic wrap for the season. Wrapping prevents the container from cracking while providing one more layer against cold air temperatures. Any covered plan parts need breathable material to remove during daylight or when they get wet.
Create a Cozy Box
Construct a simple frame around clustered groups and fill it with insulating materials for easy protection. Use chicken wire, cattle fencing, fence panels, boards, or materials around the house to create a basic high border.
An essential step is filling the box or frame with insulating mulch, leaves, compost, or extra bags of soil. Layers of evergreen boughs around and atop the pots work well, too.
If you don’t have the time or means to construct a frame, you can purchase kits online. You’ll still need to find ways to insulate it in very cold weather.
Leaf Bag Insulation
Have extra fall leaves? If you’ve already made the most of autumn’s natural leaf drop and still have a bounty of leaves, fill a few bags not for hauling away but for insulating outdoor growers.
Leaf bags create an insulating boundary around vessels and borderline hardy in-ground shrubs, too. Line bags around the specimen for added warmth. Or, pile leaves around crowns and sides to buffer freezing temperatures.
DIY Temporary Cold Frame
A rustic, do-it-yourself cold frame is easy to arrange using straw bales to form four walls. Place an old window, thick plastic, or piece of plexiglass on top to allow in natural light.
Cluster plants together within the frame and lay the cover in place. Check water needs regularly during the season. On warm days, remove the top for ventilation.
Screen
A screen offers protection against drying winter winds. In wind-prone sites, create a makeshift break by staking burlap around the exposed sides of planted arrangements. Staple the fabric onto wooden stakes or tie them to rebar supports and secure them in the ground with a mallet. Use walls or hedges to form the other sides of the barrier.
Planted Storage
To reap the benefits of in-ground soil mass, un-pot and plant or “store” the specimen in the ground. Come spring, repot it for its container display. Garden storage might be a handy trick if the plant is ready to be bumped up to a larger pot, making the timing convenient. Get it in the ground before the first frost and topdress generously with mulch.
Trenching is another technique for larger shrubs like roses, where the whole pot and plant are turned on their side, placed in a trench, and covered. A covered trench insulates both the branches and container roots. Herbaceous perennials may not require such measures, but if you have a large plant to protect, prune it back and try this in extreme conditions.
