Purifying the Air We Breathe
By Neil Moran
After lengthy studies fit for a government agency, the folks at NASA have definitively established that indoor plants can help astronauts breathe cleaner, less toxic air while in outer space. What NASA found in a study they performed in conjunction with the Associated Landscape Contractors of America, is that houseplants can effectively remove chemicals that foul our indoor air, including formaldehyde and benzene, two known carcinogens.
Here on planet earth, houseplants also serve a vital role in keeping the air clean in our homes and workplaces.
Here are a few tips to growing houseplants that will keep us healthy.
The key to growing air-purifying houseplants is proper placement and consistent care. In general, houseplants like to be placed in areas with humidity around 45 percent, which is a desirable range for most homes. What they don’t like is environments that are extremely dry, which is often the case when they are placed near electric heaters and the like. Conversely, they won’t thrive where cold drafts prevail.
Houseplants have different requirements for light, but most prefer filtered light over direct sunlight. If a south-facing window is your choice for plant placement, a thin, partially transparent curtain will help filter the harsh light, especially in Summer when our days are much longer and the sun is much more intense. Some plants, like geraniums and hibiscus, will actually thrive in the direct sunlight, while rubber plants will do better in a shady corner.
Many people often proclaim, “Give me a houseplant and I’ll kill it.” Or, if a plant looks sickly or the leaves are turning yellow, they insist it needs fertilizer. Most likely, the culprit is overwatering or underwatering. The ideal method to water most houseplants is to provide a good soaking of room temperature water, then let it dry out and water again. There are exceptions to the rule: African violets and poinsettias enjoy a constantly moist growing medium.
Always provide good drainage. Remove any decorative baskets or plastic wrap your houseplants came in from the store or garden center. Also, check to make sure that there are drainage holes in the bottom of the pot. And while it’s fine to set plastic coasters under the pots to catch excess water, don’t let standing water accumulate. The cold water in the trays is as harmful as not providing proper drainage. Finally, pick a good time to water and try to stick with it. A weekly schedule is ideal; if you miss a week your houseplants won’t die, but several weeks of neglect and you’ll be accused of being a plant killer.
Growing Your Houseplants
Houseplants will benefit from a quality houseplant growing medium. The mix should be a loose, sterile blend of soilless ingredients, including sphagnum peat moss, perlite and vermiculite. I like to “bulk up” this mixture by tossing in a few of my own ingredients. Lately, I’ve been adding a handful of fine clay used for potting bonsai, to help retain moisture. A third of the ingredients in my pots is Dairy Doo, a product manufactured in Michigan. I use their 201 mix, which includes — you guessed it — cow poop, along with worm castings and other organic amendments. Fear not, the mixture doesn’t smell bad and it is also sterile.
A light feeding of a houseplant fertilizer will keep your plants looking nice and green and help to fend off insect and disease problems. I usually use a slow-release fertilizer that will keep them fed over about a three month period, or a light, monthly feeding of a fertilizer specifically formulated for houseplants.
Pests and Disease
The first line of defense for insects and disease is prevention. This is particularly true of disease problems like fungus and mildew, which are much easier to prevent than treat. Keep your plants healthy by following the tips in this article. And always use sterile mixes for potting and repotting and keep leaf litter cleaned up. Also, be careful of bringing plants in from outdoors or from a friend down the street. Infestations are common from these sources and can be easily avoided. Fungus problems, like powdery mildew can be controlled by treating with a fungicide as a preventative measure.
Despite your best efforts, it is still quite possible to be plagued by insects and disease. There are about a half dozen insects that will try to undermine your efforts to grow nice houseplants.
Aphids, spider mites and scale are common sucking-type pests that will go after your houseplants. The tell-tale sign of an infestation of these critters is a sticky substance on the leaves. Aphids, a very tiny soft-shelled insect, will appear as a cluster under the leaves and around the stems. A spider mite infestation is evidenced by thin webbing throughout the upper portion of the plant. Spider mites thrive in warm, dry conditions. Scale is a hard shell insect that appears as brown spots, mostly on the leaves. Schefflera is particularly susceptible to scale. To a lesser degree, you may encounter white flies and thrips, at least we did in the greenhouse. You can use a plant-based insecticide containing pyrethrum to control these bugs.
A good initial treatment for all of the above infestations is to take the plant outdoors in warm weather and wash the insects off with warm water. Once it is dry, spray the plant with a plant-based insecticide, such as that containing pyrethrum. Safer and GardensAlive are two companies that sell plant-based pesticides. Quarantine the infested plant from your other houseplants. Severe infestations may warrant discarding the plant in the dumpster.
Plants that filter toxins, such as formaldehyde, xylene and even small amounts of carbon monoxide, from the air:
Spider Plant (Chlorophytum comosum)
Boston fern (Nephrolepsis exaltata bostoniensis)
Marginata (Dracaena marginata)
Peace Lily (Spathiphyllum)
Chinese Evergreen (Aglaonema modestum)
Golden Pothos (Epipremnum aureum)
Areca Palm (Chrysalidocarpus lutescens)
English Ivy (Hedera helix)
Snake Plant (Sansevieria trifasciata)
Aloe Vera (Aloe barbadensis)