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Article Published January 14, 2015

Healthy Indoor Ecology Key to Winter Houseplant Happiness

By By Kathy Connolly
The red poinsettias are still pretty. A tall, white amaryllis preens on a sunny windowsill. Nearby, a pink cyclamen graces the dining room table. It's all delightful, until the insects start.
Can we lose the insects and still keep the flowers? According to greenhouse grower Nancy Ballek Mackinnon of Ballek's Garden Center in East Haddam, we can. She and her team grow several thousand indoor species at their retail greenhouse where, on a recent visit, I found myself in a riot of flowering houseplants.
"Several factors are conducive to indoor insects at this time of year," she says. "Our indoor spaces have their own ecology, and when conditions become right, there are outbreaks."
Among those factors are shortened days, very dry indoor air, plants that are below their peak of summer vigor, overwatering, and insect life cycles. Houseplant pests often arrive many months before they emerge. The eggs can lie dormant more than a year-and then the insects emerge when conditions are right.
"Ants, for instance, can bring the eggs of scale insects and mealy bugs indoors in the spring," says Ballek Mackinnon, pointing out two of the most common indoor pests. Cats and dogs bring eggs into houses, too, as do shoes, clothing, and tools.
The first line of defense against outbreaks is not a spray, however, but the creation of good conditions.
"Put the right plant in the right place," says Ballek Mackinnon. "Don't place a sun-loving plant in a shady corner. Don't put a water-loving plant over a forced hot air vent."
Plants have very real responses to stress, which, though invisible to the human eye, create opportunities for insects.
"In very dry indoor air, for instance, stomates open on leaf surfaces in a bid for more humidity. But those openings also hang out an inadvertent welcome sign for unwanted guests," says Ballek Mackinnon.
The antidote to dry air, she points out, isn't necessarily more water in the pot. Overwatering is a well-known hazard of house plant health. It can encourage fungus gnats as well as fungal outbreaks on roots.
"Get to know the water needs of each plant species individually," she says.
Brown edges on plant leaves don't necessarily mean you should reach for the watering can.
"Often, it's a symptom of low humidity. You may need more moisture on the leaf, not the roots."
Misting is often the answer, a practice that lowers houseplant stress. In the greenhouse, Ballek Mackinnon dissolves a product called Superthrive in the mister once a month.
"It's got Vitamin B and plant hormones, which act in plants like they do in humans-as catalysts to a transfer of energy, in this case from the roots to the leaves and vice versa."
For water-loving plants, Ballek Mackinnon includes a handful of long-fiber sphagnum moss in potting mixes both because of its water-retention properties as well as its anti-fungal benefits.
As for H2O, rainwater is the way to go-particularly nitrogen-enriched snow melt. If rainwater is out of the question, allow water from the public supply to sit for several hours or more before applying. The chlorine will mostly evaporate.
Another common source of stress in houseplants is the buildup of soluble salts in potting soil, one source of which is synthetic chemical fertilizers.
"If you see white crystalline edges on the pot, it is definitely time to change the soil," says Ballek Mackinnon.
Organic fertilizers, by contrast with synthetics, work more slowly and are often packaged with beneficial microbes. Organic fertilizers create little or no salt build up. When transitioning from synthetic to organic, however, you may see a slowdown in plant color and blossoms for a short time while the soil microbes become established and ultimately become the primary purveyors of plant nutrition. You can be certain you are using an organic product if it has the OMRI label.
At Ballek's Garden Center, the team uses 15 beneficial insects according to need and conditions. "That gives us 90 percent control," says Ballek Mackinnon.
They get the remaining 10 percent from low- and no-toxicity products such as sticky white fly traps, year-round spray oil for indoor pests, and neem oil products. She recommends the book Knowing and Recognizing: The Biology of Glasshouse Pests and Their Natural Enemies by Malais and Ravensberg for deeper insight into natural controls.
Indoors and out, the wild kingdom rules. By accepting the ecology of our indoor spaces, we can better enjoy what plants have to offer year-round-color, beauty, a pleasant ambiance, and healthier indoor air.
Kathy Connolly is a landscape designer, garden writer, and speaker from Old Saybrook. Email her at and visit her website at