Cooler temperatures and falling leaves are a signal for those with houseplant outdoors to move them indoors soon. Nighttime temperatures dipping down into the 40-degree range damages some house plants.

House plants such as rubber trees, philodendron, pathos and even Christmas cactus are actually tropical understory plants. The cell structures of these plants contain more oils and waxes than endogenous plants. Waxes and oils within the cells solidify under waning night temperatures and rupture cell walls. Cold damage is manifested by internal browning on the leaf margins. Rubber tree plants are easily damaged at temperatures of 42 degrees.

The indoor environment is a difficult transition for most houseplants coming in from their long summer vacation. Outdoors, sunlight can be nearly 10,000 foot-candles, whereas indoors light intensity drops dramatically to 5-15 foot-candles, often initiating premature leaf drop. Ficus trees, or weeping fig trees, are very sensitive to deviations in light intensity, often experiencing premature leaf drop. New leaves adjust well to low light levels.

It is important to create an indoor environment similar to the outdoors. Move house plants to an area indoors that has high natural light. Avoid placing plants near drafty doors or forced air heating vents.

Occasionally mist house plants or group plants on pans of rock filled with water. Evaporating water increases the level of humidity around the plant.  Implementing an electrostatic humidifier to the room is an excellent method of keeping the air moist.

House plants on outdoor vacation this past summer are also subjected to a number of insect pests. Check house plant foliage and stems for aphids, scales or other insect pests carefully before bringing indoors.

Use recommended house plant sprays to control insect pests outdoors a few days before bringing them indoors for their winter rest. Eggs and immature stages of spiders, ants and other insects may be lying dormant in the soil media of the house plant. Plants with insects may want to drench the soil media three days before moving indoors with an indoor insecticide. Drenches will control many, but not all insects hibernating in the soil. Always read and follow pesticide labels before applying any pesticide.

Fertilization is generally not recommended on house plants during the winter months. High soluble salt build-up from winter fertilization often burns the roots, reducing vigor and eventually kills the house plant.

Darrell Blackwelder is the retired horticulture agent and director with the North Carolina Cooperative Extension Service in Rowan County. Contact him at deblackw@ncsu.edu .