The key to saving our tender plants during the cold months is overwintering. Sometimes the practice is as simple as bringing a potted plant indoors, but for in-ground plants and those too large to move, there are certain steps to take to keep plants alive during winter.
Firstly, you need to know if your plant is hardy in your zone. Go to the United States Department of Agriculture website and find your zone. Then look up your plant’s hardiness. If it isn’t hardy in your area, you need to know how to overwinter the specimen.
What Is Overwintering?
The term refers to the practice of providing extra protection to plants for the winter season. New plants, tropical and subtropical plants, and those that fall outside your hardiness zone will need that extra protection. Plants in containers will also benefit from a few steps to keep the root zone from freezing.
Overwintering practices can help ensure the next season's buds and fruits, prevent animal damage, and keep the plant safe from icy winds. With some precautions, overwintering plants can save you money, ensure the plant’s survival for years, and allow you to grow species that aren’t hardy to your region.
Overwintering Container Plants
Smaller plants can be overwintered by bringing them into a frost free zone. This might be the basement or attic, or they may thrive in the main living space. Treat plants with insecticidal soap prior to moving the containers indoors. Cut back plants that die back.
Certain plants like Caladium can be lifted from the soil once the foliage begins to yellow in late summer to early fall. Let the bulb dry out for a couple of weeks and then store it in a paper bag or cardboard box lined with peat or sawdust.
Plants that grow from roots may have the entire container moved indoors or you can heel them in. This is where you dig a trench and lay the roots in so the plant is at an angle. Fill around the roots. This keeps the plant lower to the warmer ground and protects the roots.
Large plants in containers may be covered if a freeze is expected. Bubble wrap and burlap are popular choices to keep the container warmer. If a freeze is coming, lightly cover over the entire plant with frost barrier fabric. You can also use a sheet or other covering, just remember to take it off the plant during the day. Make sure to water a container pot thoroughly prior to a freeze. Moist soil holds more heat than dry soil.
How to Overwinter Plants in the Ground
Plants that are tender and are in garden beds will need different sorts of protection. The first step is to mulch. Use organic or inorganic mulch to cover around the root zone and add a layer of protection. Bark, dried grass clippings, straw, pine needles, newspaper, cardboard, or rubber mulch are all options. Keep the soil around the plants moist if there isn’t natural precipitation.
Most plants will become dormant in winter but they do need moderate moisture, however, not as much as during the growing season. To prevent damage on woody and widely branched plants, gently tie up the branches or erect support posts under slender branches to protect them from the weight of snow.
Herbaceous plants are often cut back when their foliage and stems begin to die in fall. Instead of cutting them back then, wait until spring. The effect is a bit unsightly but the remaining structure of the plant will create a warmer space when snow falls or ice houses the plant.
Overwintering Structures
Where plants are well established and cannot be moved, erect a simple support structure around them. This can be made from wood stakes, PVC pipe, rebar, or other materials. The idea is to provide a place to settle a protective covering.
- Stretch burlap, frost barrier fabric, or even old blankets over the frame and secure it. Do not prune plants before housing them in this manner.
- Smaller plants may be protected from freezes by erecting hoop houses over them.
- Moving the plants to cold frames provides a warmer environment ambiently.
- Cloches are useful for small plants.
- If you have a greenhouse, plants can be dug up and potted and moved to this warmer location. Avoid pruning plants late in the summer season. This can cause new growth that is more sensitive to the cold. Even with overhead protection, these plants will still benefit from a layer of mulch at the root zone and light watering during dry periods.