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.
Metal planters are another great choice as they are durable and sturdy. These are frost proof planters that can be left outside without worry, year-round. However, with this material, in comparison to the fibreglass planters, there are more precautions to take. Metal can conduct the cold more than fibreglass.
Care of Terracotta Pots
It is our view that terracotta pots are not 100% frost proof, nor for that matter are other similar materials such as concrete or cast iron. Nevertheless, as terracotta is porous, water is absorbed into the pot during wet conditions.
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.
The easiest way to protect from a freeze is simply by covering plants with a sheet or a blanket. This acts like insulation, keeping warm air from the ground around the plant. The added warmth may be enough to keep a plant from freezing during a short cold snap.
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.
Fabric coverings will prevent the freezing air from coming into direct contact with the moisture on the plant while also capturing the heat that is radiating from the ground. Bed sheets or comforters work best for covering large plants and shrubs.
Plastic can be used to protect plants from frost, but it's not the best or most effective material. In fact, the horticultural experts here at Green Impressions actually recommend against it.
Extra pot: Insert your pot into a larger pot for additional protection. Bury: You can plant and pot into the ground (only 2/3 of the way so water can drain away from the pot) and insulate with leaves, straw, or mulch. During freezing temperatures, cover the branches with a floating row cover or a sheet.
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.
To protect planted terra-cotta and glazed containers left outdoors, wrap the sides of the pots with layers of bubble wrap or burlap covered with plastic wrap to prevent them from absorbing additional moisture once the plants go dormant and their water requirements are minimal.
Because they're porous, they absorb moisture like a sponge. Changes in the temperature, or freezing rain and snow can cause them to crack as the clay expands and contracts.
Synthetic materials like plastic, fiberglass, and metal are popular choices for outdoor planters. They are more durable and weather-resistant than natural materials and come in various shapes and sizes.
Light freeze - 29° to 32° Fahrenheit will kill tender plants. Moderate freeze - 25° to 28° Fahrenheit is widely destructive to most vegetation. Severe or hard freeze - 25° Fahrenheit and colder causes heavy damage to most plants.
When Should You Cover Plants? Cover your plants at night and remove them during the day when the temperatures rise above 32 degrees F, so that the soil can warm up again. Some outdoor plants won't survive the harsh conditions of winter, bring them inside and use these tips for caring for them through winter.
Most plants prefer a temperature of no less than 60° F, though many can tolerate as low as 40° F. Along with this, while the improper temperature can certainly be an issue, fluctuations in temperature are the true killer.
Leaving terracotta pots out in the winter can cause damage. There ARE steps that can be taken to help prevent your pots from cracking when old man winter whips through your garden. The goal is to eliminate the possibility of water being absorbed, frozen and thus causing the pot to crack.
Both fiberstone planters and plastic planters are perfect for leaving outdoors, however, some plastic pots do require more care as neglect can cause them to crack as freezing soil expands as it freezes inside them during cold weather.
You can overwinter potted perennials in an unheated shed or garage. Allow them to naturally go dormant in the fall before moving them inside. Then put them back outside once the weather starts warming back up in late winter or very early spring.
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. Well, we have temperatures forecast to dip into the 40s again on Thursday and lower 40s on Friday.
Semi-hardy cool-season crops (beets, carrots, Swiss chard, lettuce, cauliflower, potatoes, parsley) grow in minimum daytime temperatures of 40 degrees and higher. They cannot withstand hard frost without some kind of covering or protection.