I'm sure you 've had the same problem I do now: aphids on your houseplants. We've had them outside all summer, and they never showed signs of any aphids. But bring them inside and we have those little bugs sucking their juices out (because there are no good bugs inside eating those pesky aphids).
Aphids are less than a quarter of an inch long, often clear or light brown, and leave stickiness all over the leaves. What's a person to do? First, you should wash the plants before they move indoors. I put them on the lawn and spray them with a vigorous stream of water from the hose. Not enough to rip leaves, but a good strong spray. It is important to get both sides of the leaves washed, the stems, and the soil surface. That's right, turn the plant on its side and spray the soil to wash off eggs or aphids lurking there.
If you have already brought in your plants, inspect them daily for signs of aphids. I know the plants that, year after year, are most susceptible to aphids. I keep them in isolation, even if I have washed them off. I love my potted Impatiens that I have on the north-facing deck all summer, and want to keep them over from one year to the next — but I know I will have aphids on them. And someone gave me a potted Meyer lemon tree — in part because it is a magnet for aphids.
Another technique to minimize aphids only works on things like rosemary, which is somewhat frost hardy: leave them outside to go through a few frosts before bringing them in. That will allow Mother Nature to kill off the aphids for you. But be careful — it's easy to kill off plants if it gets too cold.
Then there is the "let-it-go-dormant" approach to tender plants. Many houseplants were originally from Africa or other tropical places. If they go dormant in their native country during the dry season, you can probably let them go dormant for you here. I have let my oxalis and ginger plants get completely dry for months at a time, and they come back to life when watered in the spring. They should not be kept in a warm room, however, so try to keep them at about 50 degrees, and preferably in a dark room — or in a brown paper bag.
Plants that have been outside all summer get cranky when brought inside, but you can help their attitude by providing the right amount of light and water. Too much water is a common cause of root rot and plant death or decline. Outdoors there are nice breezes to evaporate excess water in the soil, summer temperatures are warmer, and sunshine is stronger. So water only when the soil is dry to the touch an inch down.
If you know your plants and pots, you can tell if water is needed just by hefting the pot. If you have city water, it has chlorine in it, and many plants do not like chlorine. But that's easy to fix: plan ahead. Fill a pitcher of water in the evening, and most of the chlorine will evaporate by the next night. Or you can use brook water, rain water — or heck, Perrier, if you want!
Light is another issue. The glass of your windows absorbs a lot of energy of the sun; it's why you cannot get a tan indoors, even lying in the sun room all day with the Sunday New York Times. Sun-loving plants are the hardest to please. This year I have set up some LED lights over three of my large plants. These lights use much less energy than fluorescent lamps (28 watts to get the equivalent of 250 watts of standard incandescent light), and are sold specifically for growing plants. Mine are from Sunshine Systems (www.sunshine-systems.com or 866-576-586), their Glow Panel 45. Each panel has 112 little red or blue LED lights. I put mine on a timer so they will turn on and off automatically. They are not inexpensive, but should last for 50,000 hours. I shall see this year if that supplemental light will make a big difference to my plants.
South facing windows are best for sun-loving plants. Get your plants as close to the glass as you can, I put several pots in a big window in a rubber boot tray that I got from Gardeners Supply Company (www.gardeners.com or 888-833-1412). The tray keeps spills from getting onto the floor.
Humidity is a problem for some plants in winter, especially orchids. You can increase the moisture around your plant by putting the pot in a saucer filled with gravel. Keep water in the saucer and it will evaporate, while avoiding the problem of roots sitting in standing water, which is almost universally bad for plants. Knowing your houseplants and what their needs are is half the battle of having nice ones.
The best book I have encountered on caring for houseplants, and the specifics on individual plants is no longer in print, but is readily available in used bookstores. It's called "Making Things Grow: A Practical Guide for the Indoor Gardener" by Thalassa Cruso. If you do get aphids, even after washing them outdoors, spray them with Safer Soap, a product that is safe and easy to use — or or take them with you the next time you shower!
Henry's web site is www.Gardening-guy.com.