How to grow healthy, happy houseplants

Houseplants are like tropical fish: You start out with a dinky goldfish bowl, and before you know it, you want an entire aquarium wall. The same thing can happen with houseplants. You buy one small pothos from the discount store, and soon a room without a towering euphorbia or draping English ivy looks downright naked.

That may have something to do with the color green—it has a soothing effect that helps people relax. But houseplants do more than lower stress and keep green thumbs limber through the heart of winter.

Studies show that some houseplants remove toxic chemicals from indoor air. Your health can benefit from distributing live greenery throughout your house, rather than leaving it clustered around a sunny window like a mob scene from "Invasion of the Plant People." Think of houseplants as accessories that can be moved around, and follow these tips to successfully integrate them into your home.

1. Display an uneven number of houseplants in a grouping.Three, five, or seven plants look more interesting than two, four, or six plants.

2. Know when to water. Houseplants often are killed by kindness—most people overwater and overfertilize. Ninety-nine percent of your indoor plants like to get nice and dry between drinks. There are exceptions, so you need to know your plants' needs. Peace lilies, for instance, are heavy drinkers and quickly wilt when dry. But desert cacti need a good drink only about once a month, and no water at all while dormant from November to March. Consider using moisture-testing meters to take the guesswork out of watering.

3. Display only healthy plants. Relegate your weary-looking plants to a sunny back room for rehabilitation. Houseplants can be kept healthy in dim locations by periodically rotating them to brighter light. Some people buy two of each plant so they can switch them regularly without altering a room's decor. If you rotate plants, make sure you do it every three or four weeks.

4. Provide adequate light. Although plants thrive in homes with sunrooms and skylights, even houses with squinty windows and cramped spaces can go green. Plants like dracaenas and bamboos don't require strong light. And special lighting, such as pole lamps or overhead fixtures with circular fluorescent bulbs, can turn the dimmest corner or tabletop into a garden.

Interior plantscapers (look under "Plants, Interior" in the Yellow Pages) and some garden centers offer houseplants especially acclimated to grow in lower-light conditions. (This involves exposing a plant to successively lower levels of light over a period of months.)

5. Use plants with a variety of leaf colors and textures. Contrast foliage colors and textures to add depth and interest to a grouping of plants. To tie the group together, put plants in pots of the same size (if plant size permits), color, or material.

6. Pick the right plant for the space. Before making a purchase, figure out the size and shape of plant you need and where you plan to put it. Are you looking for a tall accent piece to set off a furniture grouping? A trailing vine for a bookshelf? A centerpiece for the dining room table?

Next turn to a good indoor-plant book or a professional plantscaper for advice on which plants will work in that space. Which ones can take the heat of the kitchen or tolerate your fondness for long, steamy showers?

7. Add humidity. What's good for your respiratory system is good for plants. In winter, humidifiers—either freestanding or built into the central-air system—help alleviate dry indoor conditions that are hard on houseplants, furniture, and people. To raise humidity levels, you can also cluster plants together (leave room for adequate air circulation) and set plants on trays filled with gravel and water. Make sure the water level stays below the bottom of the plant pot.

8. Stagger plant heights. Instead of lining up small plants such as African violets on a windowsill, place them at different heights so your eye moves up and down. Place smaller plants around the base of a tall one for added interest.

9. Choose plants and containers that complement your decor. If you're fond of antiques, you might choose a Victorian favorite such as Boston fern. Yucca and cacti are natural accents for Southwestern decor, while dracaenas and bamboos go well with Oriental furniture. In addition, make sure the pot style matches the plant. An Oriental-looking dracaena will show itself best in a china pot, but a desert yucca looks more at home in terra cotta.

B>10. Keep it cool. Overheated homes are unhealthy for plants. Although plants vary in their temperature needs, many prefer a daily variation between day and night temperatures, with ranges between 60oF and 75oF in the day and 60oF and 65oF at night.

11. Don't overdo it. Once houseplant mania takes hold and spreads, the condition is rarely curable. But remember, too many plants make rooms appear cluttered.