Sunday, December 2

Bringing plants indoors for winter

Prepare for ‘hibernation’

Simple shop lights can simulate sunshine during long, dark winter days.

The temperature has dropped and snow will be coming more frequently and staying on the ground longer, so there’s just no way we can deny it: Another gardening season has come to an end.

Now that our outdoor plants are joining their indoor cousins as houseplants, here are a few tips to help ease the transition and keep everyone healthy and happy as we hunker down and wait for spring.

Before they move indoors
Plants that have spent the warm months outside should be cleaned up before they’re brought in so unwanted hitchhikers don’t come in with them. Visually inspect plants for obvious signs of insects or disease. Spray the foliage with a stiff stream of water from the hose to knock off hangers-on, followed by a treatment with insecticidal soap. Then submerge the container in water for a few minutes. This will drive out most soil-born pests.

Heat, light and humidity
Once the plants and containers have been cleaned up and drained, transition them for indoor life by getting them accustomed to lower light, dryer conditions and less active growth. For a couple of days, move plants from sun to outside shade for a few hours during the daytime and to a porch or other protected area at night. Then, leave them in the same shaded, protected area during the day and bring them indoors at night for a couple of nights. Finally, bring them inside full time.

Once inside, the perfect location is that famous “sunny, south-facing window.” But if you don’t happen to have one stretching floor to ceiling that you can dedicate to houseplants, group those plants that need the highest light levels together and give the rest artificial sunshine. A ficus, for example, can sit beneath an ordinary floor lamp with a new high intensity, daylight fluorescent spiral bulb. Or set aside an area under four-foot shop lights hung on chains from the ceiling.

Use the “daylight white” tubes and set the lights on a timer. If you’re supplementing sunshine, set the timer to run three to four hours before sunrise and three to four hours after dark. If you’re holding plants in an area without natural light, run the timer for eight to 12 hours on a regular schedule.

Even tropical plants prefer 65 degrees Fahrenheit to 75 degrees Fahrenheit indoor temperatures. More important is temperature stability. A brief blast of cold air can stress a plant as much as putting it outside all day, so keep them out of drafts.

Watering and fertilizing
Research your plants’ individual water needs. Generally big, fast-growing, flowering plants with large leaves need more water than plants with small, leathery, waxy or soft leaves.

To create a humid environment and slow moisture loss in dry winter air, cluster plants together and place them on gravel or small stones in a shallow tray of water. Make sure the bottoms of the containers stay dry.

Dry plants are lighter than wet ones, so lift the containers to check for soil moisture. Or, press a finger into the top inch of soil. If it’s dry, it’s time to water.

Use tepid water, never cold, to saturate the soil and let the container drain completely in the sink. Soaking the soil to capacity moves oxygen into the roots and leaches out any accumulated salts.

Overwintering is about holding and resting plants, not necessarily actively growing them. So use fertilizer very sparingly, and apply organics. Those fast grow “miracle” products actually kill the soil and turn plants into chemical addicts. Dilute any of the many organic products available today to 25 percent of the recommended concentration and wet the soil with water before applying the food.

Dealing with critters
Close indoor conditions can promote bugs. White flies, mealy bugs, scale and powdery mildew are common culprits. If the infestation is light, try yellow sticky traps or biological predators and parasites such as ladybugs and Leptomastix wasps, available from specialty gardening sites on the Net. Heavier problems call for soap sprays, neem oil or a 50:50 mix of isopropyl alcohol and water. Horticultural oil or botanical pesticides like pyrethrin are the big guns. If the infestation is totally out of control, its time to cut your losses and remove the plant.

Winter is the season of rest, but also of promise. Keeping our plants safe and stable while the snow flies is an act of faith that spring will come again, and we’ll all be ready for it.

Active in the horticultural industry since 1994, Glen O. Seibert is a former editor for Garden Gate magazine and now works as a writer, landscape designer and self-professed “gardening media mogul.”