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NASA experts conducted a Clean Air Study to determine which common houseplants best removed contaminants from an indoor environment. Although NASA and the Associated Landscape Contractors of America conducted the study in 1989, their findings are still useful to gardeners today.

Two of the most effective houseplants tested were peace lilies and snake plants. A green thumb is not required to grow these plants, but a few facts will make for healthy, thriving plants.

Peace lilies (Spathiphylumm) have always been a popular choice for homes and offices. Although considered easy care plants, proper growing conditions are still important. Most commonly, these plants have dark green leaves and white “flowers.” Actually, the “flower” is a specialized leaf bract.

The plant enjoys medium to low light. More light will tend to increase flower production, while less light will make a more traditional foliage plant. The most common mistake is over-watering. Simply touch the top of the soil and water only if it feels dry. If the soil is still damp, do not water. Some might even say go so far as to allow the plant to start to droop before watering. This will not hurt the plant and will prevent over-watering.

They do not require frequent fertilizing; once or twice a year with a balanced fertilizer will be sufficient. Wash or wipe leaves to remove dust at least once a year. Avoid commercial leaf shine products. Re-pot the plant when you note drooping leaves shortly after watering or note deformed leaf growth.

The second best air filtering plant was the snake plant (Sansevieria trifascista), or better known to many as Mother-in-Law’s Tongue, Vipers’ Bowstring Hemp and Saint George’s Sword (in Brazil). It is one of the most popular houseplants, as well as the most unusual in appearance.

In reality, the variety known as snake plant usually has green banded leaves, while the variety called Mother-in-Law’s Tongue typically features a yellow border. This plant can withstand virtually all conditions from dark to light. The only SURE way to kill it is to over-water or never water at all. Let the soil dry between watering and reduce the watering to monthly during the winter months.

The plant prefers warm conditions and suffers if the temperatures are less than 50 degrees. Fertilizer should be limited to a mild cactus fertilizer during the growing season, with no fertilizer in the winter. Divide snake plant when re-potting in the spring, if needed. Always use fresh potting soil.

A few easy care sun seeking houseplants to consider are hen and chicks (naturally sprout new baby plants even with little water intake) and aloe (very useful for burns – just bust open a piece of the leaf and apply directly to the burn). Both of these plants require little watering.

Hopefully many readers enjoyed the Coles County U of I Extension Master Gardeners’ Conference last Saturday at Lifespan in Mattoon. If you didn’t attend, mark your calendars to attend Spring into Gardening next year in February 2019.

If you have other questions about your garden or landscape, feel free to contact a Master Gardener volunteer at the University of Illinois Extension office in Charleston at 217-345-7034. You can also check out the many horticulture webpages at the U of I Extension’s website by visiting And be sure to like the Master Gardeners’ Facebook page at


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