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.
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.
Suitable plants
Try box (Buxus sempervirens), bay (Laurus nobilis), skimmia, euonymus, ivy (Hedera) or Gaultheria mucronata varieties. Ornamental cabbage and kale provide additional foliage interest.
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.
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.
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 solution is to buy the winter pansies in September and pot them up from trays to 5″ pots and let them develop until the time is right (usually October) for transfer to their final location for the winter. Alternatively, buy the larger plugs but expect to pay much more for them.
Metal, plastic, and fiberglass are safe choices. Some ceramic containers can withstand a freeze, if they've been fired at high temperatures. And while standard concrete might break, concrete mixed with polymers stands up better. Wooden planters weather pretty well, too.
Metal. Metal containers are extremely durable, and in the case of cast iron, they can be extremely heavy. Said toughness makes them likely to last for many years, if they're taken care of properly.
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.
having been fired at a higher temperature. Frank Organ. Frostproof pots. “Frostproof” pots should be just what the name implies, able to survive any amount of frost, as they are fired to a high temperature resulting in a pot that does not allow water to soak into it.
Frost-resistant and frost-proof containers
Plastic and fibreglass pots are frost-proof, as are many glazed ceramic pots. Unglazed terracotta pots have a porous structure that allows the pot walls to absorb water. This works well in summer, as excess water can seep out and the soil can breathe.
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.
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.
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.
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.
One of the best ways of preventing your pots from freezing and breaking is to use Pot Feet. Pot feet come in a variety of shapes, sizes and colors, but the purpose is the same, to raise the pot up off of the surface and allow water to drain out freely.
If they're small, turn them upside down and store them in place. A winter garden in a concrete container. Concrete pots can stay out all winter and look best if you plant them. In this pot are evergreen boxwoods, evergreen 'Cintronelle' heuchera, and evergreen ivy.
Strength – Metal containers are extremely strong and durable. They won't chip, crack, or scratch, and can be left outside to age with no problems. Galvanized steel is even stronger and will be more weather-resistant compared to other planters in your container garden.