Neil Moran gardens on Michigan’s Upper Peninsula, where he is a freelance writer. A former greenhouse manager, he is the author of North Country Gardening: Simple Secrets to Successful Northern Gardening; From Store to Garden: 101 Ways to Make the Most of Garden Store Purchases; and North Country Gardening with Wildflowers: A Guide to Growing and Enjoying Native Plants in the Great Lakes Region.

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Clean the Air with Houseplants
by Neil Moran       #Containers   #Environment

Cluster air purifying plants to create a green scene.

After lengthy studies, 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, 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.

In addition to adding beauty, texture and fragrance, houseplants also serve a vital role in keeping the air clean in our homes and workplaces. Here are a few tips for growing healthy houseplants that just might help keep us healthy.

Pothos trails from an end table.

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 an environment that is extremely dry, which is often the case when placed near indoor heat sources. Conversely, they won’t thrive where cold drafts prevail, either.

Light Requirements
Not all houseplants have the same light requirements. Most prefer filtered light to 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 longer and the sun more intense. Some plants, such as 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 over- or under watering. More plants are killed with kindness than neglect. The ideal method to water most houseplants is to provide a good soaking of room temperature water, then let it dry out before watering again. There are exceptions to the rule: African violets and poinsettias enjoy a constantly moist—but not wet—growing medium.

Always provide good drainage! Remove any decorative baskets or plastic wrap your houseplants might have come in. Check to make sure that there are drainage holes in the bottom of the pot. Although it’s fine to set plastic saucers or trays under the pots to catch excess water, don’t let the plant sit in standing water for more than about an hour.

Root bound plants, like this wandering Jew (Tradescandia) should be transplanted to a slightly larger pot or split up into multiple plants.

Choose a 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 after several weeks of neglect you’ll be accused of being a plant killer.

Potting mix
Houseplants do best in a quality 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 mixture in my pots is a sterile compost or other organic amendment. This material results in improved water- and nutrient-holding capacity and better-looking houseplants.

A light feeding with houseplant fertilizer will keep your plants nice and green. It also will help the plant fend off insect and disease problems. A slow-release fertilizer will keep plants fed over a three-month period. Or use a light monthly feeding of a water-soluble fertilizer specifically formulated for houseplants. Always read and follow the label instructions.

Pests and Disease
The first line of defense for insects and disease is prevention. This is particularly true of disease problems, such as fungus and mildew, which are much easier to prevent than treat. Always use sterile mixes for potting and repotting and keep leaf litter cleaned up. Be careful when bringing plants in from outdoors, from a friend down the street or the garden center. Infestations are not uncommon from these sources and can be easily avoided.

These plants are easy to grow and will 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)

Give new plants a shower or quarantine them for a few weeks of observation before introducing them to your other houseplants. Fungus problems, such as powdery mildew, can be controlled by treating with a fungicide as a preventative measure on plants susceptible to the disease.

Despite your best efforts, it is still quite possible to be plagued by insect and diseases. At least with insects we know who’s showing up for dinner. There’s about a half dozen insects that will try to undermine your efforts to grow nice houseplants.

Sucking Insects
Aphids, spider mites and scale are common sucking-type pests that will go after your houseplants. The telltale 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 a 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 whiteflies and thrips—at least we did in the greenhouse. You can use a plant-based insecticide containing pyrethrum to control these bugs. Always read and follow the product’s label instructions.

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. In cold weather, give the plants a shower in the bath tub, sink or shower. Once dry, spray the plant with a plant based insecticide.

Quarantine the infested plant from your other houseplants. Severe infestations may warrant discarding the plant in the dumpster.



A version of this article appeared in a January/February 2013 print edition of State-by-State Gardening.
Photography courtesy of Neil Moran and Proven Winners.


Posted: 01/16/18   RSS | Print


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