While some plants can survive light frosts, others will die as soon as their cells freeze. Depending on their hardiness, some potted plants will respond to the first frost by going dormant just like garden plants do. However, as the temperature continues to drop, their roots might die unless they are protected.
Clay or terracotta pots are prone to cracking in frost so either avoid using these for your winter displays or look for frost-proof pots and containers. Plastic, fibreglass, wooden and treated terracotta and clay are all good materials for winter pots.
Fiberglass, lead, iron, heavy plastic, and stone are the best weather-resistant containers to use; terra-cotta will eventually expand and crack with repeated freezing and thawing.
In the Winter Planter and Window Box, I used spruce tips, cedar branches, balsam, white pine boughs and dyed eucalyptus. I added in some faux, waterproof berries and some pine cones on picks. I love the different textures and the color contrasts.
Japanese yew (Taxus cuspidata) is a good choice for an outdoor winter plant because it's an evergreen that keeps its leaves on its branches all winter long. It's drought-tolerant and thrives in both full and partial sun. Hardy to Zone 4, Japanese yews can survive harsh winters.
The only plants that don't go dormant during the winter are annuals, which are only capable of surviving for a single growing season, and must be replanted each year for continual enjoyment.
Annual Plants
Crabgrass, petunias, and snapdragons are types of annual that will not survive cold temperatures and will need to be cared for to survive winter.
Because the soil will expand and contract greatly over a harsh winter, those who grow where the ground freezes hard should empty out plastic, ceramic and clay pots to protect them from cracking. Or you can just bring the whole schmageggie inside to a place that will remain above freezing.
And they do just fine. The key to success with garage storage is that this area is attached to the house but not heated. The garage never goes below 32 degrees but tends to hover in the 40's and low 50's all winter. This keeps the plant dormant but the plants never freeze.
If it is not going to rain before the freezing temperatures arrive, you should water plants thoroughly. This is because moist ground stays warmer than dry ground. Watering the night before the freeze arrives will insulate the root structure of the grass and plants, decreasing the potential for cold injury.
Pansies. Remarkable as a winter plant, Pansies can survive freezing coldness and can thrive vigorously when summer returns. Its “smiling face” flowers are vibrant in color and fragrance that can fill up your space with so much joy.
Leafy vegetables like cabbage, lettuce, kale, collards, and chard can tolerate some frost. Early spring blooming flowers like crocus, snowdrop, and primrose can all survive the winter, and pansies are especially resilient.
Fall and Winter LEAFY GREENS
A beautiful sampling of some of the leafy greens you can grow in your fall and winter garden, including different varieties of kale, spinach, lettuce, chicory, and even wild chickweed! Spinach is a very fast-growing, cool weather vegetable.
From winterberry and paperbark maple to witch hazel and pink muhly grass, these winter plants are pretty, yet tough. They shine brightest in cold weather, because they add height, texture and structure to your backyard space. Plus, many of these colorful winter plants have wildlife benefits.
Ornamental kale and cabbage are some of the most popular winter annual plants. They lend a completely different texture to a winter landscape bed. Once the plants are hardened by cooler night temperatures they can survive most cold winters.
Pansies and Violas
These adorable flowers with little “faces” come in every color of the rainbow, and they don't mind a chill—so they'll last into late fall or early winter in many climates. In the South, they'll survive throughout most of the winter.
Winterizing Your Planter
This can be done by adding substrate below the soil at the bottom of the planter, adding properly sized drainage holes at the bottom of the container and using high quality potting soil. This also prevents the plants from getting waterlogged. Make sure the planters aren't directly on the dirt.
You can wrap pots up to help keep the compost and plant roots warm. A couple of layers of bubble wrap is a great insulator. Or make 'pot duvets' from black plastic bags filled with straw or shredded paper. They look a bit odd but they will keep the soil warm.