By Greg Seaman Common indoor plants may provide a valuable weapon in the fight against rising levels of indoor air pollution. NASA scientists are finding them to be surprisingly useful in absorbing potentially harmful gases and cleaning the air inside homes, indoor public spaces and office buildings. The indoor pollutants that affect health are formaldehyde, Volatile Organic Compounds (benzene and trichloroethylene or TCE), airborne biological pollutants, carbon monoxide and nitrogen oxides, pesticides and disinfectants (phenols), and radon. These pollutants contribute to ‘sick building syndrome’, which causes symptoms ranging from allergies, headaches and fatigue through to nervous-system disorders, cancer and death. Dr. B.C. Wolverton, researcher and author of “How to Grow Fresh Air – 50 Houseplants that Purify Your Home or Office”, conducted plant studies for NASA and assigned plants a rating from one to 10, based on a plant’s ability to remove indoor air toxins, ease of growth and maintenance, resistance to insect infestation and the rate at which water evaporates from the leaves. Top plants for removing formaldehyde, benzene, and carbon monoxide: Areca Palm (Chrysalidocarpus lutescens) Also called the “Butterfly Palm”. An upright houseplant that is somewhat vase shaped. Specimen plants can reach 10 to 12 foot in height. Prefers a humid area to avoid tip damage. When selecting an Areca palm look for plants with larger caliber trunks at the base of the plant. Plants that have pencil thin stems tend to topple over and are quite difficult to maintain. Lady Palm (Rhapis excelsa) This durable palm species adapts well to most interiors. The Rhapis are some of the easiest palms to grow, but each species has its own particular environment and culture requirements. The “Lady Palm” grows slowly, but can grow to more than 14’ in height with broad clumps often having a diameter as wide as their height. Bamboo Palm (Chamaedorea seifrizii) Also called the “reed palm”, this palm prefers bright indirect light. New plants will lose some interior foliage as they acclimate to indoor settings. This plant likes to stay uniformly moist, but does not like to be over-watered or to sit in standing water. Rubber Plant (Ficus robusta) Grows very well indoors, preferring semi-sun lighting. Avoid direct sunlight, especially in summer. Young plants may need to be supported by a stake. The Ficus grows to 8’ with a spread of 5’. Water thoroughly when in active growth, then allow the soil to become fairly dry before watering again. In winter keep slightly moist. Dracaena “Janet Craig” (Dracaena deremensis) Easy to grow, these plants do best in bright indirect sunlight coming from the east/west. They can adapt to lower light levels if the watering is reduced. Keep the soil evenly moist and mist frequently with warm water. Remove any dead leaves. Leaf tips will go brown if the plant is under watered but this browning may be trimmed. Philodendron (Philodendron sp.) One of the most durable of all house plants. Philodendrons prefer medium intensity light but will tolerate low light. Direct sun will burn the leaves and stunt plant growth. This plant is available in climbing and non-climbing varieties. They need to be misted regularly and the leaves kept free of dust. Soil should be evenly moist, but allowed to dry between watering. Dwarf Date Palm (Phoenix roebelenii) A hardy, drought-tolerant and long-lived plant, the Dwarf Date Palm needs a bright spot which is free of drafts. It grows slowly, reaching heights of 8-10’. The Dwarf Date Palm has sharp needlelike spines arranged near the base of the leaf stem. These can easily penetrate skin and even protective clothing. Boston Fern (Nephrolepis exaltata “Bostoniensis”) These feathery ferns which are best displayed as a hanging plant. It prefers bright indirect sunlight. Keep the soil barely moist and mist frequently with warm water. This plant is prone to spider mites and whitefly which can be controlled using a soapy water spray. Peace Lily (Spathiphyllum “Mauna Loa”) The Peace Lily is a compact plant which grows to a height of 3’ with a 2’ spread. This hardy plant tolerates neglect. It prefers indirect sunlight and high humidity, but needs to be placed out of drafts. For best results, the Peace Lily should be thoroughly watered, then allowed to go moderately dry between waterings. The leaves should be misted frequently with warm water.