Wrap pots in burlap, bubble wrap, old blankets or geotextile blankets. It isn't necessary to wrap the entire plant because it's the roots that need shielding. These protective coverings will help to trap heat and keep it at the root zone.
Take out old plants and half of the soil from high-fired glazed containers to allow for water drain during the freeze/thaw cycles. Elevate pots left outdoors using pot feet or bricks so they are not sitting directly on the ground. Drained water can pool, freeze pot to the ground and cause wear and tear on planters.
One way or another, when a warm spell during winter is forecast to be followed by a cold snap, make sure to protect not only the pot and the roots but also the top of the plant. Cover plants with plastic film, burlap, blankets or other cloth material at night.
Store your flowerpots out of the elements, if possible.
Ideally, you'd store them someplace that stays above freezing temps, like an attached garage. That way, pots that are vulnerable to freeze damage and breaking (like terracotta pots and ceramic pots) are less likely to crack and break.
Planters made from modern substances, like fibreglass, fiberstone, and non-porous plastic composites can safely remain outside over winter. Fiberstone planters are made from a mix of limestone and fibreglass, which forms a material that looks like stone but weighs a fraction of the natural material.
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. Assemble your designs early enough that the plants have time to acclimate to their new pots before the hard freeze.
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.
Once the first hard freeze has occurred, apply 2 to 4 inches of straw, pine needles, hay, compost, leaves, bark chips or other organic mulch evenly around the plants.
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.
It depends on the temperature, and specifically the nighttime low temperatures. You'll want to move your houseplants indoors before night temperatures get below 45°F. Any colder, and you're likely to see damage, especially on tender new leaves and stem tips.
If the pot is too heavy to turn over, wrap it with heavy plastic to guard against water entering and freezing. If soil is left in the container, ensure its bone dry and covered. Plastic or stone perennial-plant-filled containers can be left out over winter, if you follow a few simple procedures.
Winter Care of Your Porch Pot
You can mist the greens with water once or twice to help keep them fresh. Wilt-Pruf can be used on fresh-cut greens to lock in the moisture with a wax-like coating once they are planted in your pot. When outside temps freeze the soil in your porch pot, you no longer have to water.
You can also cover pots with a board or piece of metal weighed down with a brick or stone to make sure snow and ice don't collect in the container. The biggest problem then isn't the pot breaking but the glaze flaking. You can turn the containers upside down on the deck or patio.
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. Watering is needed, but not too much or too often.
Whether it's hostas, daylilies, ornamental grasses, evergreens or everbearing strawberries, not only can perennials provide big interest and color in their pots, they also have the advantage of being able to grow again year after year. Well, that is, as long as you can protect them over winter!
If you leave the soil in your containers and moisture gets in the soil, the soil can freeze and expand, damaging your pots. Even resin (plastic) pots can get freeze damage and crack open.
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.
From that experience, I've found the best frost protection for your outdoor plants is either free or cheap. Cardboard boxes and brown grocery sacks make perfect frost cover and at the end of the season can be recycled. I keep various boxes on the patio and when frost is forecast simply put one over the plant.
Choose The Right Containers
Terra-cotta and ceramic pots absorb moisture, which expands as it freezes and cracks the container. Metal, concrete and wood containers typically handle freezes well, as do fiberglass and resin pots. Some plastic pots also survive winter fine, but may become brittle over time.
A covered porch usually provides protection from light frost, but the garage or sun room is better for freezing temperatures. A couple days in darkness won't hurt the plant. Or move them out during the day and back in at night, if cold temperatures persist.
I did some research and found out that houseplants need to be taken indoors before overnight temperatures dip below 45 degrees. Most tropical plants suffer harm from temperatures below 40 degrees.
Cover Plants – Protect plants from all but the hardest freeze (28°F for five hours) by covering them with sheets, towels, blankets, cardboard or a tarp. You can also invert baskets, coolers or any container with a solid bottom over plants. Cover plants before dark to trap warmer air.