Preparing Houseplants for Winter

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With temperatures expected to drop into the 40’s and 50’s, now is the time to bring your tropical plants and houseplants back indoors to protect them from the upcoming cold weather. Most tropical plants suffer at temperatures below 40 degrees; a few are damaged below 50 degrees.

Because temperature, light, and humidity vary widely between the inside and outside of your home, a gradual reintroduction to the indoors is best. A sudden change in light may cause yellowed leaves, dieback, and leaf drop. Prepare for your houseplants by cleaning your windows, both inside and out, to ensure plants can get adequate light. Gradually expose your plants to less light by placing them indoors where they can get the brightest light possible, usually a south-facing window or under plant lights on a timer for 16 hours a day. After a few weeks you can move the plant to its permanent home. Some leaves will still drop during this process, however new ones should develop as the plant readapts to the lower light. Schefflera, sansevieria, orchids, orange and citrus trees, cacti and succulents are plants that perform best and should be placed where they can receive high light intensities.

Indoor plants need less water and fertilizer than those grown outdoors. Overwatering is a primary reason many plants do not survive indoors. Allow the soil surface in the pot to get dry to the touch between watering; succulents are watered even less often. Don’t water if it is very cloudy or raining as plants in window sills won’t get sufficient light indoors to dry out. Fertilize your plants one final time as you bring them in and avoid fertilizing until next spring. Fertilizing plants that are not actively growing results in buildup of fertilizer salts in the soil causing damage to roots and marginal burn of leaves.

Inspect plants for insects and diseases and treat as appropriate before bringing them back inside. Plants exhibiting a sickly appearance may have become infested with insect pests or infected with a disease-causing organism while outdoors. This initial problem may become severe when you bring the plants indoors because the disease or insect’s natural enemies are not in your home. Black, brown, or yellow spots may indicate a bacterial or fungal leaf spot disease. To combat foliar diseases, pick off and destroy affected leaves, leave plenty of space between plants, move them to a less humid area and do not wet foliage. Viruses are transferred to healthy plants by insects and on human hands. Controls do not exist for viral problems so discard diseased plants. Soil-borne organisms cause root and stem-rot diseases, which usually occur under very wet soil conditions. Avoid overwatering plants and provide good drainage to prevent this problem.

Common houseplant insect pests are aphids, mealybugs, whiteflies, scale, spider mites and thrips. Insecticides usually are not necessary on small infestations limited to a few plants. Dip a cotton swab in rubbing alcohol to remove light aphid and mealybug infestations or use tweezers or your fingernails to control them. Wash off mites by spraying plants with water. Use a solution of two tablespoons of mild soap per gallon of water and a soft brush or cloth to eliminate heavy insect infestations. If you decide to use a conventional insecticide, always read and follow the manufacturer’s label instructions. Check the outside of the pot for signs of unwanted inhabitants. Soaking the pot in a tub of lukewarm water for about 15 minutes will force insects out of the soil. Repotting may eliminate pests such as snails, spiders, or ants that took up residence in potting soil.

Repotting is also necessary if plants have developed crowded roots during the summer. Remove the rootball from the pot. If the rootball is a mass of roots with very little soil showing, it needs repotting to a larger container. If the rootball looks fine but the pot is top heavy from growth, prune back some of the growth.

For more information, contact the Christian County Cooperative Extension Service, 270-886-6328.