| Choose Plants That Fit a Cool Indoor Environment |
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By Lindsay Bond Tottens
Scripps Howard News Service One size hardly ever fits all -- and that goes for houseplants as well. We choose varieties that appeal to us, sometimes without paying much attention to the "fit." Indoor environments differ substantially, just like outdoor environments do. Heat source, supplemental humidity and exposure to natural light create microclimates within homes, sometimes even within the same room. Human comfort levels vary, too, ranging from thermostat settings of 60 degrees F to near 80 degrees, often with cooler temperatures at night as we dial down to save energy. Conservation efforts reward indoor gardeners with lower fuel bills. But don't expect indoor plants to necessarily be pleased about it. Houseplants can't reach for a sweater. Their ability to compensate for lower temperatures depends on several factors. Some we can tinker with -- reducing the amount of water and fertilizer we give them, for instance. Lowering the thermostat gradually will coax some varieties to adjust as well. But the bottom line is determined, for the most part, by a plant's genes. Gardeners can increase their chances for success by choosing plants that "fit" a cool indoor environment. If a plant's ancestors came from a climate that enjoys warm, sunny days but where temperatures plummet at night, as in some deserts around the world, chances are that houseplant will be a good candidate for a coolly sunny room in your house. Many cacti and other succulents fall into this group. Hoyas, pencil cactus, sansevieria -- also known as mother-in-law's tongue -- burro's tail, echeveria and jade plant are just a few varieties with a high tolerance for low temperatures. Comfortable with nighttime settings that dip into the 50s, some will go even lower, as long as they don't freeze. Kalanchoe, a popular holiday gift plant, will bloom for many weeks if kept on a very cool, brightly lit windowsill. Swedish ivy, coleus and many varieties of ferns are forgiving of challenging indoor climates. All will contribute lovely foliage to a collection of houseplants that like cool temperatures. Among the specimens that will actually bloom at rock-bottom thermostat settings are oxalis, jasmine, camellias and florists' azaleas. Be careful, however, not to test those lower limits with a treasured Christmas or Thanksgiving cactus. Though succulents, these plants come from warmer, moister regions of the globe and are not amused by chilly nights, especially when in bud. Low temperatures can cause the flower buds to "blast" -- shrivel up and fall off without opening. Of course, pots of forced bulbs are exceptionally responsive to cool sunny indoor spots. Once their chilling requirements are satisfied -- usually 10 to 12 weeks at 38 to 40 degree temperatures -- colorful combinations of tulips, daffodils, hyacinths, grape hyacinths, crocus and snowdrops will gradually unfold their petals in even the chilliest room. In fact, cool temperatures help bulb blooms last longer and encourage the foliage to stay shorter and stockier, requiring less staking as the flowers open. If a few more degrees of comfort can be mustered, around 55 degrees at night, indoor gardeners can add streptocarpus to the list of blooming plants above. Lovely clivias, as well as a few varieties of fancy-leafed begonias, will also bloom within this temperature range. Though all these plants like supplemental humidity, none wants it directly on its foliage. Avoid overhead misting of these and other houseplants growing in cool temperatures. Moisture on leaves is slow to evaporate and can cause spotting of leaf surfaces or rotting of entire leaves and crowns. Supply humidity by placing plants on a pebble tray filled with water. Be sure to change the water frequently. Better yet, use a room humidifier or whole-house humidifier to add moisture to the air inside your home. Seasonal beauties like cyclamen, cineraria, pocketbook plant (Calceolaria) and freesia are also popular among indoor gardeners for their willingness to brave the cold while blooming cheerfully. And once Christmas and Thanksgiving cacti have shed their holiday blooms, the foliage is perfectly content to share windowsill space for the rest of the winter with the 55-degree group. Water less frequently, however, if you do move them to cooler quarters. Plants will tell you when they're shivering. Look for older leaves turning limp and yellow. These may begin to fall off. Other signs include flower buds blasting and new leaves that are smaller than normal and slightly curled. Revive them by moving them to a warmer room. (Lindsay Bond Totten, a horticulturist, writes about gardening for Scripps Howard News Service.)
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