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.
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.
Even an unheated garage or shed is typically enough to keep tender plants in an above-freezing environment. Potted tropicals and houseplants should move inside even if temperatures don't drop below freezing. Many of these suffer damage even at 40 degrees.
Believe it or not, trying to grow plants in the depths of winter isn't off the table. That is, if you have adequate heating. A space heater or solar lamps is all you need to keep the garage warm enough for plants to thrive. Keep in mind that the hotter the room is, the more light and water your plants will need.
It is a good idea, though, to give the pots just a little bit of water every few weeks over winter. The goal is to keep the soil from going so bone-dry that the roots shrivel and die, but not so damp that you encourage new shoots to come up in the somewhat-warmer temperatures of your garage.
The plants can then spend the winter in an unheated basement, root cellar, unheated garage, or even a cool closet. Make sure the area is relatively dark (try enclosing the whole pot loosely inside a heavy black trash bag) and that the air temperature stays above freezing.
Bury the pots or bring them inside.
Simply dig a hole and plant the perennial pot and all. This way the soil in the pot will benefit from the temperature-stabilizing mass of the ground soil. Alternatively, bring the pot into an unheated, not-too-bright interior space, such as a garage or cold cellar.
Know Your Plants' Cold Tolerance
Some frost-tender plants need to be covered as soon as the temperature hits 32°F, while others can handle lower temperatures and/or longer freezing periods. You'll need to look up each of your plants to verify its cold tolerance.
On woody plants, the leaves will yellow and drop off. Keep the dormant plants dry, but not so dry that the soil becomes powdery. Check soil moisture often and if very dry, lightly water. In most situations, light watering will be needed every two to four weeks.
You can put them in a garage or shed that gets cold but doesn't freeze, ever. They will over-winter as live but semi-dormant plants. Keep the soil just moist, not letting the potting medium shrink and pull away from the pot edges.
In all but the mild-winter regions, potted plants grown on terraces and rooftops, where they will be exposed to chilling winds, should be moved to a sheltered location, such as close to a building or near a pergola or other structure, away from high winds and winter sun.
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!
With adequate rainfall, established plant species appropriate for our climate typically need little to no supplemental irrigation during the winter. Exceptions to this rule include newly planted trees and shrubs, plants in containers, and periods of unusually dry winter weather.
Give These Plants a Winter Rest Indoors
Or, you can cut back their foliage and store their pot somewhere cool and dark. If you store the whole pot inside, it is important to keep them slightly moist, so their roots or bulbs don't shrivel up completely.
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.
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.
Indeed, a plant that is drought stressed will often show more damage after a light freeze. So if they are dry, always be sure to water your potted plants before a freeze to help them better handle the cold.
An unheated garage, shed, or basement with a temperature range between 30 and 40 degrees can provide a perfect environment for overwintering perennials.
Potted plants will do well in your garage if they are insulated. If they are not, then you may have to take some extra precautions. One of the precautionary measures is to make sure that you place something between the pots and the floor.
Most plants need some light in order to grow, but shade-loving plants can easily get by with indirect light, or even artificial light from regular light bulbs.
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.