Q: I've heard that plants can help moderate indoor temperature. Can they make my apartment warmer in the winter?
A: I'm pretty green to hardcore botany issues, but I've done a little digging. There seems to be lots out there on how temperature affects plants, and much less on the reverse. One source says plants can make a hot, stuffy room more bearable by releasing oxygen. Another calls photosynthesis a kind of solar-powered cellular factory. (Picture the little worker plant cells getting all hot and sweaty as they produce oxygen.) But the truth is, most plants don't give off heat. I've even wondered whether they're hoggin' all the warmth of the light coming through my windows. That said, a few flowers get a little steamier than most, so much so that some, like skunk cabbages, can even melt snow. Certain ancient plant lineages like magnolias, star anises and water lilies actually get hot under the, um, flower to lure pollinating insects. If you can get your hands on the Voodoo lily, for instance, you'll find that the inside of its massive purple flower can reach strangely scalding temps of up to 110F in the shade. Of course, its popularity as a houseplant is kind of undermined by the rotten meat smell it gives off during pollination. Ick.
Beyond such thermogenic plants, the kind of temperature regulating you're talking about might be true for greenhouses and biodomes, but they're made of glass, which obviously traps a lot more sunlight than most homes. (Unless you're one of those people who live in glass houses. And you know what we say about them.) Better to get a caulking gun and rid your pad of drafts. (See last winter's column on heating tips for more ideas, www.nowtoronto.com/issues/2005-01-13/goods_ecoholic.php.)
That's not to say plants don't have wonderful and very useful qualities. Did you know they emit serotonin-boosting negative ions? Greenery seems to speed up recovery in hospital rooms and boost worker productivity in office spaces. Maybe that's why computers come with all those pretty forest screen savers.
Plants also do a lot to boost indoor air quality, which is particularly handy at this time of year when we've battened down the hatches to keep the cold out. About when Cyndi Lauper and Duran Duran were first hitting it big, NASA tested a dozen common houseplants to see how well they filtered out chemicals commonly found in the air in offices and homes (namely ozone-depleting volatile organic compounds like formaldehyde and benzene - scary!). Their conclusion? Plants are really good at absorbing and destroying certain organic chemicals and converting them into an energy source. Pretty amazing, really - although the California Air Resource Board poo-poos the research, saying plug-in air filters are better.
According to NASA, the most effective filters overall were Chinese evergreen, Peace lily, Arrowhead vine, spider plants, English ivy, cornplant and Devil's ivy. Generally, the bigger the leaf surface, the higher the transpiration rate and the more chemicals are absorbed. Some plants are better than others at ridding the air of particular chems. Formaldehyde , found in pretty much everything including particle board, pressed wood, grocery bags, facial tissues, water repellants and wrinkle-resistant fabric coatings, is most quickly removed from indoor air by Boston ferns, then dwarf date palms, followed by bamboo palms. Gerberas and chrysanthemums are good at filtering out carcinogenic benzene. The researchers recommended placing a plant in your "personal breathing zone" at work (within 6 to 8 cubic feet). One on every desk would be ideal.
If you've got a small forest of plants in your apartment and are worried about excess humidity and mould spores, know that the plants themselves aren't the problem. However, your soil might be. Just cover it with 2 inches of gravel or anything pebbly.
For those of you fretting that your houseplants are quietly robbing you of oxygen at night, relax. According to a U.S. Department of Energy website, it would take hundreds of pounds of plants in your bedroom to emit as much carbon dioxide as one human sleeping next to you. If you're still paranoid, get a succulent, orchid or bromeliad; they all add oxygen to the air at night, so you can breathe easier.
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