Excerpted from Rodale's Successful Organic Gardening: Houseplants and Container Gardens.
Successful organic gardeners know that if you choose the right plants for your conditions, plant them in healthy soil, give them fertilizer and water judiciously, and react sensibly to problems, your garden will be beautiful, productive, and undemanding. The same holds true of houseplants. Here's what you need to know to care for potted plants the right way—that is, organically.
The right light
Begin by observing the places where you want to put houseplants. Knowing how much light each spot gets will help you determine the right plants for that spot. "High" light is found directly in front of most south-facing windows, and large unobstructed east or west windows. Smaller unobstructed east or west windows yield "medium" light. North windows and those that are shaded offer only "low" light. Your plants will get only low light if they are more than a couple of feet from a window facing in any direction.
Carefully read plant tags before you buy to identify suitable choices for each spot in your home. As a rule of thumb, flowering plants require high light, while many foliage plants thrive in low light.
Shop around for houseplants—prices and quality can vary widely. Garden centers, home centers, florists and even supermarkets sell potted plants. When you find a plant you want, choose a balanced, evenly shaped specimen. If you've decided on a flowering houseplant, look for one that has plenty of buds, with just a few flowers beginning to open.
Finally, inspect each plant thoroughly to be sure it does not have disease or pest problems. Gently tug on the leaves to be sure they don't pull off too easily—a sign of an unhealthy plant.
Houseplants suffer as much from overwatering as they do from underwatering. To determine if your plants need water, push your finger about an inch or so into the pot's soil. If the soil feels damp, check again in a few days. When the top layer of soil is dry, water the plant.
Bear in mind that plants growing in clay pots dry out faster than those in plastic pots. Also, plants growing in "high" light need water more frequently those in "low" light. And, plants use much more water during the long, warm days of summer when they are actively growing than in the short and cool days of winter.
When you do water houseplants, give them a thorough soaking so that a little water runs out of the pot's drainage hole and into the saucer. This flow of water through the soil is beneficial because it pushes out used air and allows fresh air to move into the spaces between soil particles. Plants' roots need air as well as water.
If water goes straight through the pot and out the bottom, the potting soil has become so dry that it has contracted and left space where the water can run through. To water dried-out soil, set the entire pot in a bowl or sink full of water to the pot's rim and let the soil slowly absorb the water. After the soil is wet, let it drain and then return it to its saucer.