Common houseplants: eye pleasing and air purifying

By Kathy Hatfield
Gardening Columnist

When NASA was searching for a way to reduce the high level of air contaminants given off by equipment in the confined quarters of the space shuttle, they found that many common houseplants can lower the levels of certain air pollutants.

Many of us live and work in areas that have questionable air quality. While we often hear of the dangers of cigarette smoke, or we are cautioned about breathing the fumes from paints and varnishes, there are numerous other contaminants in everyday products.

Many of these are known carcinogens. Three common indoor air pollutants are benzene, formaldehyde and trichloroethylene. Benzene, a known eye and skin irritant, can also cause headaches, nervousness, drowsiness and anemia. It is found in oils, paints, dyes, detergents, gasoline, pharmaceuticals and synthetic fibers. Formaldehyde, found in wood products and adhesives, is also a contaminant of permanent press clothing, foam insulation and carpet backing. It is an irritant of mucous membranes and can cause upper respiratory problems, headaches, asthma and possibly a rare type of throat cancer. Trichloroethylene is used in the dry cleaning industry and is also found in printing inks, lacquers and varnishes. It is considered a potential liver carcinogen.

From the NASA studies, plants that were most efficient in absorbing benzene from the air are English ivy, dracaena and peace lily. To absorb formaldehyde, spider plant, dracaena, mother-in-law's tongue, philodendron, bamboo palm and golden pothos were top performers. Dracaena and peace lily were also tops for removing trichloroethylene.

Bamboo palm (Chamaedorea), which can grow to 8 feet tall, is a great plant if you have a large area with bright filtered light. These plants have smooth green stems knotted at intervals like bamboo. Keep the potting soil for bamboo palms thoroughly moist.

Dracaena (Dracaena spp.) is a striking houseplant with its long ribbon-like leaves and statuesque habit. Many have variegated foliage, some have narrow leaves with reddish margins, and one variety has leaves more like those of sweet corn, giving it the common name "corn plant." Dracaena likes bright light, but not direct sunlight. Keep the potting mixture moist, but not soggy.

English Ivy (Hedera helix) is a small, woody-stemmed climbing plant. Its trailing foliage and leathery, often lobed leaves make this an attractive addition to indoor containers. English ivy likes bright light with some direct sun. Water thoroughly during active growth, allowing the soil to dry slightly between waterings.

Golden pothos (Scinpadsus) provides a nice bit of contrast with its irregular yellow markings on green leaves. The shiny heart-shaped leaves will lose most of their contrast if light levels are not adequate. Bright filtered light and moderate watering are best for this tropical native.

Mother-in-law's tongue (Sansevieria) is also known as good luck plant, devil's tongue and bowstring hemp. Most have attractive marbling on stiff upright leaves. They like bright light, especially direct sunlight, and will tolerate shade for only a short period of time. Moderate watering is best, but allow the top to dry slightly between waterings.

Peace Lily (Spathiphyllum) is sensitive to direct sunlight and will show its distress with scorched leaves. This plant responds best with moderate watering. Fragrant flowers on rigid stems are usually produced in the spring or summer. When they start to discolor, cut them at the base.

Philodendrons (Philodendron spp.) vary considerably with different leaf shapes, colors, and sizes, from smooth-edged and heart-shaped to large, deeply lobed leaves. As young plants, many of these have a particular leaf shape that matures into something entirely different as the plant ages. All varieties need moderate watering and bright filtered light to keep their appealing leaf qualities.

Spider plant (Chlorophytum) is also known as ribbon plant. Its ornamental habit and easy care make this a favorite. The main plant produces plantlets at the end of long stems that can easily be rooted and passed on to plant-loving friends. Spider plant requires bright light, preferably some direct sunlight, and enough water to keep the soil moist during active growth.

The NASA study has been criticized for testing plants under conditions that do not reflect real life because of the enclosed testing environment. But even if the results are not directly relevant, houseplants reduce carbon dioxide levels, increase humidity and add beauty to homes and offices. Some of the most attractive houseplants are not only the easiest ones to grow, but they can also provide us with a healthier indoor environment.