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Keeping annuals as houseplants

Some gardeners buy annuals or tropical plants every summer and eventually let them die. Others among us -- the frugal, sentimental or just plant-lovers -- can't stand to toss a good plant. We try to keep them going as houseplants, to use outside again next season. Many plants perform well in our homes, if we meet basic needs. Others make it only if we provide a cold period or greenhouse-like conditions. Some plants, we learn the hard way, are just as well turned into the compost heap in the first place.

Which plants are worth trying to keep beyond September, and which ones fit which category? With so many plants available and rampant hybridization, it's all somewhat experimental. Here is what experienced growers report:

Indoor requirements

Light, temperature, humidity and water (quality and practices) make or break the suitability of your indoor setting.

Consider, for example:

* Light: Your brightest window probably offers less light than full shade outdoors. Most outdoor "shade plants" will do well in your bright window or with supplemental lighting. Most "full sun" plants may not survive and certainly won't flower in indoor house conditions. Direct sunlight in a window is a problem, too, as glass intensifies light and plants may burn. Some shade plants that generally do well indoors are Coleus, Impatiens and Begonias.

* Temperature and humidity: The warmer the room, the more humidity you must provide for most plants. But, for some, it will never be enough. Ivies, Schefflera and Impatiens get spider mites if the room is too hot and dry. Other plants get scale or just dry up.

* Make changes slowly: Plants will drop fewer leaves (a sign of shock) if you adjust them to the light change. From their outdoor summer spot, move them to outdoor shade for a week, and only then into your brightest indoor spot.

> Houseplants used outside

Using houseplants and tropicals in containers is a huge trend today. Old plant friends are showing up in mixed baskets on decks everywhere: Abutilon (Flowering maple), Coleus, Dracaena, Philodendron and Spathiphyllum. The beautiful Plectranthus is popular now in many fuzzy-leaved varieties, but it's really our dear old Swedish Ivy in fancy forms; 'Troy's Gold' is spectacular!

Many newer trendy container plants also come indoors well: Alternantheras, both kinds of Breynias, Cordyline. Others (not new) might surprise you as good houseplant choices: Clivia, Clerodendron, Dipladenia and Passion flower vine.

> Maybe nots

You can always try, but if you can't offer a particular environment, some plants won't make it. Caladium needs a humid conservatory. Ivies (among many others) get spider mites and scale insects if they are kept in a dry, warm room. Heliotrope should be wintered at 50 degrees -- an unusual situation for most homes. And Mandevilla and all those sunny basket flowering plants? Probably not.

Sally Cunningham is a garden writer and former Cornell Extension educator.

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