If you let your house plants "vacation" on the back deck or front porch during summer, then by late September it's time to start getting them ready to move back indoors for the winter.
Because conditions differ widely between the inside and outside of your home, a gradual reintroduction to the indoors is best. Sudden changes in temperature, light and humidity can be traumatic to plants, resulting in yellowed leaves, dieback, wilting and even death.
You should bring plants indoors before nighttime temperatures dip below 45 degrees. Most tropical plants will suffer damage at temperatures below 40, a few at 50.
Before bringing them back inside, inspect plants for insects and diseases and treat as appropriate.
If necessary, repot plants in larger containers. If they have gotten leggy during their outdoor stay, remove from the container and prune the top and roots in equal proportions. Scrub the pot, add fresh potting soil and replant.
This is also a good time to take cuttings of annual flowers, such as impatiens, begonias, geraniums and coleus. They root easily in water or sand and make attractive house plants. This is a good way to overwinter them for planting in the garden next year.
To prevent shock when you bring house plants back indoors, expose them gradually to reduced lighting. If they've been in bright light and you move
Don't overwater! Although our dry summer meant you probably had to water your container plants every day, indoors they won't require as much water. Let the soil surface get dry to the touch before watering again. Water succulents less often, when the soil is dry for several days. Don't water during quite cloudy or rainy weather, as plants won't get sufficient light indoors to dry out.
Why have indoor plants?
Master Gardener Connie Schultz of Johnston County, N.C., provides some science-based health reasons for keeping plants indoors that go beyond their aesthetic appeal.
We hear a lot these days about "indoor pollution." We know now that new homes can actually be the source of much indoor air pollution. New carpet, paint or cupboards give off volatile organic compounds, which can cause headaches, nausea or other symptoms.
People often ask me what they can do to eliminate these toxins from their homes and purify the air. Along with simple things such as opening doors and windows to allow toxic gases to escape and prevent them from building up inside the house, use indoor plants to help remove some of those harmful substances that can remain in a new home's interior for several years.
A NASA study in 1973 "identified 107 volatile organic compounds in the air inside the Skylab space station. Synthetic materials, like those used to construct Skylab give off low levels of chemicals. This effect, known as off-gassing, spreads the VOCs such as formaldehyde, benzene and trichloroethylene, all known irritants and potential carcinogens. When these chemicals are trapped without circulation, as was the case with the Skylab, the inhabitants may become ill, as the air they breathe is not given the natural scrubbing by Earth's complex ecosystem."
The NASA research showed that while all plants improve air quality, some removed toxins from the air to a greater extent than others. They identified several types of plants that were especially efficient at removing toxins and also were able to survive in low-light conditions. A University of Minnesota article lists some of these plants, listed below (The number of plants recommended to clean your air is about one plant for every 100 square feet in the home or office.)
Air purifying plants
Plants that are efficient at purifying the air of benzene are florist's mum, peace lily, "Warneckei" dracaena, Madagascar dragontree, Chinese evergreen, golden pothos, Gerbera daisy and miniature umbrella plant.
Those that fight formaldehyde include bamboo palm, "Janet Craig" dracaena, snake plant, peace lily, bromeliad, aloe, spider plant, orchids, dumb cane, azalea, philodendron and dracaena marginata.
Plants that clear the air of trichloroethylene are Madagascar dragontree, peace lily, "Janet Craig" dracaena, bamboo palm and Gerbera daisy. Energy-efficient homes
Ironically, our more energy efficient houses make indoor air pollution even worse due to their tighter construction that allows less exchange between indoor and outdoor air, reducing the ventilation present in older, "leakier" homes. Add to that other sources of off-gassing such as new couches, mattresses, cleaning supplies, copiers and printers, aerosol sprays, air fresheners, dry-cleaned clothing, insect repellents and packing foam (peanuts), to name a only few and the need to freshen our indoor air becomes even more apparent. So, take a deep breath and celebrate the fresh air provided for us by both indoor and outdoor plants.