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.
1. In order to overwinter a perennial or shrub in a container outside, it needs to be two zones hardier than the zone you live in. 2. Perennials and shrubs that are in your zone or one colder can be overwintered in an unheated garage, buried in the ground, or transplanted.
As a general rule, tender plants should be brought in when nighttime temperatures are below 50 to 55 degrees F, even if they are hardy for your zone. A plant's roots are more exposed when planted in a container versus in the ground.
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.
Unless your plants are winter-proof, it's best to move them indoors or wrap them up when temperatures are near or below freezing for more than five hours.
Cutting back perennials in the fall is not only a great way to keep flowerbeds looking neat and tidy through winter, but it also aids greatly in keeping plants vibrant and blooming the following year. Removing spent foliage and blooms helps a plant focus on recharging it's roots and resources.
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.
Keep them away from direct sunlight and heat vents, as well as cold drafts near a window or door in winter. Avoid placing your arrangement near ripening fruit, which releases tiny amounts of ethylene gas that can age flowers prematurely. And finally, most cut flowers benefit from a daily mist of water.
If you live in the heat sink of the city, leave them in the ground. If you live in one of the outskirts, where it gets really cold, take them out of the ground immediately after the first frost and store them for planting next year as above.
When To Winterize Your Gardens. The best time to start winterizing gardens is after the first hard freeze in the fall. A hard freeze occurs when the temperature gets below freezing overnight, killing off tender annual plants and vegetables.
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.
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.
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.
A fabric covering is best because it will allow moisture to escape while still protecting your plants from frost. 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.
Some Hardy Perennials Need Winter Protection in the North and Midwest, and Tender Perennials Require Special Protection Methods. Many perennials hardy for your zone make it through winter just fine with no special attention.
Perennials NOT to Cut Back
Also, do not cut back hardy perennials like garden mums (Chrysanthemum spp.), anise hyssop (Agastache foeniculum), red-hot poker (Kniphofia uvaria), and Montauk daisy (Nipponanthemum nipponicum). Leave the foliage. It's important to protect the root crowns over winter.
It's common to think that everything should be chopped down to the ground in the fall, but some perennials actually need their foliage to protect new shoots through the winter. Other varieties offer up important habitat for local wildlife and some perennials provide height and interest through the winter months.