What can I do to protect my container plants from the winter weather?

ASK THE HORT AGENT

Question What can I do to protect my container plants from the winter weather?

Answer When it comes to container plants, your concern should be their roots. The roots are far less hardy than the top of a plant. Plants growing in the soil have geothermic heat to keep their roots toasty. When plants are placed in a container, they do not have the heat from the soil that would otherwise help it overcome harsh conditions. As a result, roots of container plants are subjected to ambient air temperature. Cold weather can cause root damage and injury which may last into the growing season. There are obvious and not-so-obvious steps a gardener can take to protect plants grown in containers or planters. The most obvious answer is to move the containers inside a heated area. This may be a garage, barn, greenhouse, basement, etc…

Another obvious step includes the use of plants which are more winter hardy. Many plants are perennial in the tropics. However, they turn into annuals when the frost is on the pumpkin. Cold hardy plants are the ticket to surviving the winter.

There are less obvious steps a gardener can take to beat the low temps. First, use large containers. Choose a container at least 12-18 inches tall and 18 inches across. The extra volume of soil in a large container helps to insulate plant roots.

If your plant is in a pot which is merely sitting in an ornamental container, then the inside pot can be removed and “heeled in” the soil. “Heeled in” simply means temporarily planted in the ground. In this situation, the pot can be returned to the ornamental planter next spring. During the winter, the ground around the pot will insulate the plant’s roots.

Hardcore gardeners will group their containers together and cover them with blankets. This combination of gathering and covering helps to catch more of the natural heat which the soil radiates throughout the winter. For some people, this may create a visual problem. Residents living on a golf course may not have a suitable place to hide this frozen plant pile.

Lastly, give plants a good watering a day or so before really cold weather. Drought stressed plants are more susceptible to cold injury. Winter damage is caused by desiccation (drying out) as well as low temperatures. The moist soil is also a good "heat sink," absorbing heat during the day and radiating it out slowly on a cold night. Take care not to overwater, creating a waterlogged condition. Sprinkling the foliage and branches of plants prior to a freeze does NOT help protect them. In fact, it can do more harm than good.

For more info about containers, visit http://www.aces.edu/pubs/docs/A/ANR-1139/

If you do not have access to the internet, then call the Extension Office at 893-7533 or email me at gpierce@harnett.org

The addition of a solar room ($5,000 to $10,000) to the side of your house is a great way to protect your plants ($5 to $25 per container) in the winter. It would only take about 40 years to justify that expense.

Gary L. Pierce

Horticulture Extension Agent