Allied Florists of Houston

Being the kind of person who can't bear to let go of summer, and loath to throw away anything that can be recycled, I bring in more houseplants each fall than I put out the previous spring. I feel about plants the way other people feel about their pets (dogs, cats, snakes): They are my companions and they give me real comfort. In winter I have an overhead garden ringing my kitchen beneath two skylights. With their varied forms, foliage colors, and textures, plants make the room feel tropical and festive by their presence. In an adjacent room I have a collection of succulents and cacti grouped in small, rough, sand-colored containers. The forms are fascinating and they grow slowly enough to seem eternally frozen in time. Large, moisture-loving plants, a palm, a fern, a bromeliad, and a Christmas cactus covered in fuchsia blooms from Thanksgiving through April, decorate the largest room. It's a good idea to locate plants together with similar cultural requirements, such a moisture and light.

In addition to making a home feel cozier, there are other reasons to add plants to your indoor environments. As our homes and offices become more tightly sealed to save energy, the indoor air may be 10 times more unhealthy than the air outside, as synthetic toxins found in common building materials and furnishings accumulate. By the process of photosynthesis, plants convert our toxins into energy for their needs and oxygen for ours.

Most Americans spend 90 percent of their time indoors, yet human beings are genetically programmed to "commune with nature," according to McRae Anderson, a landscape architect and interior plantscaper. This natural proclivity toward nature has been given the name "biophilia" by Edward Wilson, the Pulitzer Prize–winning biologist. The "nature deprivation" that many of us experience when we are cooped up inside causes irritability, fatigue, and increased stress.

An organization called Plants at Work has collected data from researchers around the world showing that plants have the ability to improve our psychological and physical health by detoxifying our air, lowering stress levels, and reducing a variety of illnesses. Adding plants to our living and work spaces has been proven to lower systolic blood pressure by 10 to 15 points, create more comfortable humidity levels, and blur the distinction between indoors and outdoors. In a Norwegian study, inclusion of plants in the workplace was shown to play a significant role in reducing illnesses such as coughs, dry throat, fatigue, and headaches, resulting in a reduction in absenteeism. At Washington State University, a study showed a 12 percent quicker response time from stressed computer workers when plants were present in the room; and in a Texas study, creativity and problem solving were enhanced. Perhaps I should have sent my daughter to the SATs with a few African violets.

The scientific basis for these findings rests on biology. Through transpiration, foliage plants give off moisture, increasing the humidity levels in closed rooms by 30 to 60 percent, increasing our comfort, especially during the heating season. When plants are present, the extra moisture in the air weighs down airborne particulates and causes them to settle, thus reducing the effects of synthetic toxins that emit formaldehyde and VOCs, or volatile organic compounds. Many palms, Boston fern, English ivy, gerbera daisies, rubber plant, and peace lily are excellent at absorbing and breaking down these compounds by pulling the contaminated air to the roots where microbes convert it to food for the plant. Tulips, orchids, aloe, azalea, and cyclamen are other good bets. Some plants purify air through their foliage. Dr. Bill Wolverson, a researcher with NASA and author of How to Grow Fresh Air: 50 Houseplants That Purify Your Home or Office, calls plants the "lungs and kidneys of the home." Putting plants in the bedroom is also a good idea, since we spend so many hours there.

How many plants does it take to lower your blood pressure and detoxify your air? Have a plant within your "personal breathing zone," on your desk, kitchen windowsill, bedside table. Fifteen to 20 plants will clean a 1,500-square-foot area, or one large plant per 100 square feet.

I think it's time to chuck the silk houseplants and head to the greenhouse to bring home some tropical sunshine in a pot to satisfy the biophile in all of us.