Gardening Tips: Preparing for Frost

— Written By and last updated by Chrissy Poole

After a long summer, it seems that fall is finally here. While we haven’t had a frost yet, our first one doesn’t seem far off, as we’ve often had our first fall frost in this area around October 15th. The weather for the next week doesn’t seem to indicate an immediate risk of an overnight frost, but we all know the weather can change quickly. Generally, I consider there to be a risk of frost in scattered locations anytime the forecast is for overnight temperatures lower than 40 degrees. Typically low elevation areas and open areas in more rural locations can be several degrees colder at night than what is predicted for a city like Roanoke Rapids and temperatures can drop quickly if cloud cover and wind conditions are right.

            What all this means, is that you need to start preparing houseplants tender perennials, and any annuals that are worth squeezing a few more weeks out of for frost.

Let’s start with houseplants. Most houseplants are tropical foliage or flowering plants that are grown indoors because they can’t survive winters in this climate. Some gardeners also dig up valuable annual plants and keep them in the house over the winter. In either case, be careful before bringing these plants indoors to inspect for insect pests. Often, insects that live in the soil of potted plants, such as fungus gnats, or foliar pests such as aphids, scales, or mites will multiply rapidly in warm indoor conditions. Thoroughly inspect these plants before bringing them in and treat with an insecticide if necessary to prevent unwanted insect problems. Insecticidal soap is an excellent control for most pests of houseplants and is safe to use on indoor and outdoor plants.

            Annual flowers that are still blooming may be of high enough value to you that you want to preserve them as long as possible and there are some things you can do that may help them last for another few weeks. First, for those nights when the temperature is going to dip low, consider covering these plants with a blanket, newspaper, or light layer of pine straw. Take the covering off the following morning and replace the next night when it gets cold again. Alternatively, you can gather up any extra mulch from your flowerbeds and mound up around the base of the plants. Either of these techniques might provide an extra 2-3 degrees of insulation for these tender plants, but won’t help much when the temperatures get really low. Eventually you’ll have to accept the fate of your plants.

            Tender perennials and newly planted trees and shrubs would benefit from a good mulching prior to the onset of cold weather. Two to three inches of mulch is about standard for most plants, but if you are trying to over-winter plants that are truly on the borderline of our hardiness zone (7b), such as elephant ears, you may want to mound a little extra mulch around the base of the plant. This will help keep the soil warm for the winter, but the mulch should be thinned down to about 2-3 inches once spring comes. Tender plants like this should really be planted in protective locations, such as close to the house, or surrounded by other shrubs, where they can have some extra protection from the cold.

            Matthew Stevens is the horticulture extension agent for Halifax County Cooperative Extension. If you have any questions about this article or other aspects of your home gardening, please contact Matthew at 583-5161 or matt_stevens@ncsu.edu.