How to Protect Plants from the Cold

How to Protect Plants from the Cold

If your weather is a bit too cold or your plants a bit too tender, there are things you can do to help your garden through the winter. It all depends on how tender the plants are, how cold the weather is, how long it will be cold out, and how much energy and trouble you want to spend. For some combinations of climates and plants, no amount of extra care will keep them growing, but in many cases, a bit of extra care can bridge the gap.

1 Bring potted plants indoors. The first and easiest solution to the cold, is to simply remove your plants from the low temperatures. If you have any potted plants or hanging baskets outdoors, bring them inside your home. Even a move to the garage or a sun room will be beneficial, as this will still increase the temperature by at least 10°F (−12°C). If you’re able to, the best solution is to place your plants around the interior of your home as decoration. They’ll get the heat they need without cluttering your extra space.

Place potted plants near windows as per their sun requirements; east and west facing windows get the most light, while north and south windows get a bit less.
Avoid putting potted plants near vents, as this can dry them out and cause them to begin dying off.
Placing plants too near to a window can be damaging if it is extremely cold outside; freezing temperatures can transfer from the window to your plant if they are touching.

2Apply a layer of mulch. Mulch acts as an insulator, holding in heat and moisture in the soil. It is used to protect the root systems of your plants from cold temperatures. Sometimes the cold temperature is not what damages the plant, but rather the freeze/thaw cycle affecting the soil and causing it to "heave" the plant. Similarly, the cold soil can prevent water from easily being drawn up from the plant. Regardless of the reason, applying a layer 2–3 inches (5.1–7.6cm) thick of mulch will help prevent these problems.

Mulch made of wheat or pine straw works well, as it is easy to remove once you’re read to bare the soil again, and it traps heat well.
Certain plants, such as roses and strawberries, may be overwintered by covering them completely with a clean mulch.
Insulation works both ways. It can prevent the soil from cooling off too quickly, but it can also prevent it from warming up promptly when the time comes. You may wish to rake it back away from the plants as spring starts to warm up.[1]

3Cover your plants. Throw an old blanket, drop cloth, or tarp over tender plants. If you need to protect your plants from a small number of especially cold nights, a simple shelter such as an old blanket may be enough. Choose your covering, and then carefully spread it out so that it is not touching any of the leaves or branches of your plant. You may need to use a few stakes to prop it up, otherwise it can damage the plant. This method works best to protect from frost rather than cold temperatures, as the covering won’t increase the temperature too much.

Take it off during the day so that the plants can get light and air.
You may need to weigh or tie down the cloth so that it doesn't blow away.

4Build a cold frame or greenhouse. Build a simple, temporary cold frame by bending slender metal rods into loops and sticking the ends into the ground across a garden row. Then, place a length of clear plastic sheeting over the loops so that it encloses the plant. This will work to trap heat and block out frost, and is the best solution for keeping your plants safe and warm in the winter. On the flip side, it does require a bit of construction and is not the most attractive solution.

Build a somewhat more permanent cold frame by hinging a window or storm window to one side of an open-bottomed box built from scrap lumber.
Build a PVC Hoophouse with the instructions given here.
Make sure the plants in your greenhouse or cold frame receive adequate ventilation. Think about how warm the inside of your car gets on a sunny day. If daytime temperatures are warm, open up to allow air to circulate. If you don't, you could overheat your plants or build up too much moisture inside.

5Water your plants. Heavily water the soil around your plants prior to a very cold night or freeze. The soil will trap the heat better wet than when it is dry, and evaporate slowly which warms the air around the plants. Don't do this if you expect a hard freeze though, since it could backfire, but to protect against a little frost, a generous watering can help to retain some of the day's heat into the night.

Don’t water soil that is frozen, as this won’t help and can actually make conditions for the plants more difficult.
Don’t heavily water the soil around succulents, as they can’t tolerate the moisture levels.[2]

6Supply a heat source. If you’re undergoing a bout of extremely cold weather that your plants won’t be able to survive, you can help them out by giving them a heat source. Either cover them with a plastic tarp or a blanket or build a makeshift greenhouse (both as aforementioned) and then place the heat source inside. Possible heat sources include christmas lights or a 100 watt light bulb; these aren’t so hot as to damage the plants, but are warm enough to increase their temperature. Don’t place the heat source in direct contact with your plants; move it away slightly so that it increases the temperature without burning the plants.

Use outdoor-safe extension cords and materials so as to avoid a dangerous situation.
Uncover your plants and turn of the heat source during the day to allow ventilation. This will also help to prevent a fire from starting on an overheated light bulb.[3]

7Choose plants that are suited to your climate. This is the simplest, lowest-effort choice. Learn your which growing zone you are in (if your country has such a classification system; the US system is coordinated by the USDA) or at least your likely low and high temperatures for the year and choose plants that can withstand those temperatures. Some plants may die back, lose their leaves, or otherwise go dormant in winter, so take the time to know how plants that are well adapted to your climate handle it. The disadvantage to this approach, of course, is that it limits your selection of plants.

Annuals are plants that die back each year and must be replanted if they do not reseed themselves. In colder climates, some perennial plants may be grown as annuals if they would otherwise not survive the winter. The growing season of some annuals may be extended with shelters or by starting the plants indoors or in a greenhouse.
Perennials are plants that continue growing from one year to the next. For these, you will need to learn what, if any, additional care they require to survive the winter.
Talk to the people at your favorite nursery about what to expect from a plant during winters in your area. Also ask where to plant and how to care for a plant before you purchase it.
Look for varieties and cultivars of plants suited to your climate. There are some varieties that are bred hardier than others, making them better options for cold environments.[4]