Fall has officially arrived, but lots of gardens aren't showing it yet. Roses are still flourishing, sweet potato vines are still creeping, impatiens are still blooming -- in fact, this may be the best your garden has looked all year.
If you're one of those people who gives your garden a touch of the tropical by taking your houseplants outdoors for the summer, you have some decisions ahead. Just as you had to wait to take them outdoors until night temperatures were reliably over 50 degrees Fahrenheit, now you have to bring them in before the nights start getting cooler than 50.
Before you start grabbing pots and hauling things indoors, you need to do some planning, and maybe a little triage. Although they get lots of light and moisture outside, the plants may have acquired a few other things that are not so good, like white flies, spider mites, powdery mildew and other insects and diseases that love potted tropicals. You don't want to unleash these inside your house.
There are two approaches to having houseplants outdoors. Given the pests and the damage, some folks think it isn't worth it to try to preserve the plants. They treat them as annuals, dumping the old specimens and buying new ones for the house.
Others, for economical or sentimental reasons, are avid about saving their leafy friends. I know someone who has been nursing the same gardenia for 35 years and counting. It stays inside in cold weather and goes outdoors for the summer. A few years ago, it defoliated and almost died, but the owner was so fond of it that we tried a growth stimulant and fertilizer (Superthrive and Miracle-Gro) and sure enough, it came back.
Taking the houseplants outdoors for the summer is a great idea. You get optimum growth in the outdoor heat and humidity, and the plants get what Joan O'Rourke, a master gardener and avid volunteer at Brookside Gardens in Wheaton, calls "a nice vacation from their owners."
"We're too kind to our houseplants and tend to water them to death," she said. Many plants are more or less dormant inside during the winter. "If it weren't for that summer vacation outside, they wouldn't make it through the colder months."
Television home design and gardening shows have been featuring outdoor rooms decorated with foliage and flowers. People who have invested a lot of money and emotion in their plants might not want to dump them when cooler weather comes. But, plants are also subject to damage from wind, storms, too much rain or too little rain.
O'Rourke, a container-gardening specialist who works extensively in the greenhouses at Brookside, has some advice for people who love their houseplants and want to bring them back in:
Before you start, look around your house and see where you're going to put them. If you just start hauling them in, they may end up in the wrong place. Dracaenas, snake plants (Sansevieria) and peace lilies (Spathyphyllum) will do fine in indirect light, but schefflera, fishtail palm, ficus and croton are a bit fussier about their environment and require more light and humidity. Palms and ferns like more humid spaces. For them, a kitchen or bathroom with enough light might be ideal.
When you start scouting for places to put plants, you may find you don't have room for all of them. You might have to give up on some of them, O'Rourke warned. Examine the plants carefully to see how they are doing. Do they have insects or diseases? You will have to treat them rigorously before bringing them inside. Check all the leaves, buds and flowers. Pull each plant out of the container to check for crawling insects.
Are some of the plants performing poorly? If they don't make it outdoors in good to ideal conditions, they won't do better inside. Are some simply too big for indoor spaces? Are they going to be messy? Ferns are notorious for shedding, and most plants will drop some foliage after being moved indoors.
How will you water the plants indoors? It's true you don't have to water as often or as much in winter. The best way to water indoor plants is to take them to the tub or shower, water them and rinse them off, and let them drain. Is it going to be too difficult to do that?
Some plants are going to be dormant in winter anyway. For example, O'Rourke cuts her banana plants back and puts them in the basement. If she thinks of it, she occasionally gives them a cup of water.
Before she brings her plants in, she treats them for insects. Hibiscus plants are notorious for hiding white flies. She treats them ruthlessly, cutting them "way back." Then, as she does for all plants that are headed indoors, she treats them with insecticidal soap and horticultural oil "until they're dripping." She lets them dry out for four or five days and repeats the process.
Some people like to repot plants when they bring them inside, but O'Rourke isn't in favor of that. The plants will be stressed anyway with the changed conditions, and it's not good to encourage a lot of new growth.
Once the plants are inside, don't water them unless they need it. Overwatering is the biggest killer of houseplants. Check the pot for soil dryness -- and not just on the surface. Stick your finger down into the soil. If the soil is dry a couple of inches down, water, but make sure the pot drains thoroughly. Never let plants sit in water. The roots still have to breathe.
Although she is selective about what plants she lets back indoors, O'Rourke is a big fan of having plants in the house. They are not only lovely to look at, but also help clean the air. Among her favorites is the plain old-fashioned spider plant. She likes the way the variegated foliage really brightens up a room and uses the "babies" the plant produces in other container plantings.
Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. E-mail or contact him through his Web site, www.gardenlerner.com.