Dear Miss Floribunda, I have been very upset watching coverage of the wildfires raging in California, not only because of the people and animals who are victims, but also because of the trees. In addition to the trees that burned up like firewood, I worry about what happens to the trees nearby because of the smoke. What about crops and gardens? The smoke must be suffocating at best, and with the fumes from the cars and homes that are incinerated, it must be toxic at worst. Is this as bad as I fear? What is the long-term effect?
Heartsick on Hamilton Street
COURTESY OF SOPHIE BACKES
Dear Heartsick,
Of course you are right to be deeply concerned, but at least I can assure you that plants do have some coping mechanisms. Like us, plants can more or less hold their breath — and for longer periods of time than we can. While we breathe through our mouths and noses, they breathe through tiny pores in their leaves called “stomata.”
While we might shut our windows or wear masks to keep from breathing in toxins, trees can stop letting air in entirely. And they don’t emit any vapor, with its precious moisture as well as oxygen. In fact, during drought, trees have been known to close their stomata for weeks. Photosynthesis is, of course, then affected, and leaves will turn brown and fall off — but most trees survive and revive once moisture is restored.
My neighbor Heather Hiker actually saw first hand the effect of this phenomenon in the summer of 2000 when she visited Mesa Verde National Park, Colo., during a vacation out West, and saw the aftermath of the July 2000 Bircher Fire. After a tour of the area that she found shocking, she went to a motel for the night. During the night, rain finally fell. When Hiker returned to the park the very next morning, she was astonished to see that grass had shot up, and brown vegetation had suddenly become green. She told me, “It was like everything was suddenly coming back to life.”
It should also be pointed out that trees native to fire zones tend to have much thicker bark than those elsewhere, which keeps extreme heat and smoke from penetrating their cores while preserving moisture. Examples are sequoias and ponderosa pine. Even trees actually burned to the ground produce fire-induced sprouts that come up out of the tree’s extensive root system to begin anew. Coniferous trees growing in fire zones produce serotinous cones that are more or less glued shut with a strong resin till a fire causes the resin to melt and release the seeds that can then sprout into new trees. Ashes from the trees that have become “firewood,” as you have termed it, will nourish new growth.
However, even though trees in the vicinity of a forest fire may themselves survive, the smoke can have a harmful effect on vineyards even hundreds of miles away. The grapes suffer what is called “smoke taint.” Volatile phenols penetrate the skins of grapes and impart tastes that can range from a mildly pleasant mesquite or clove flavor to nasty tar notes that make any of its wine impossible to choke down. Research is underway to develop sprays that can be used to protect grapes once smoke detectors indicate that the air has become dangerously polluted; thicker-skinned grapes, such as those for syrah and chardonnay, are finding favor with viniculturists; and processes to remove smoke contaminants during wine-making, such as cold maceration, are being explored.
Although grapes are the fruit most vulnerable to smoke taint, lettuce and leafy vegetables can suffer short-term damage, as well. Over the years, numerous tests by the University of California, Davis; the University of Oregon; and the University of Colorado indicate that exposed vegetables, once washed, are safe to eat. Most shrubs will perk up once the smoke lifts and photosynthesis resumes. However, human beings in forest fire vicinities are not encouraged to go out and garden till the smoke has cleared. Humans have no immunity to the toxins in the air and should stay inside or leave the area. Our mobility is the only advantage we have over plants during catastrophes.
To discuss this and matters of immediate concern to home gardeners as we begin spring pruning and planting, please come to the next meeting of the Hyattsville Horticultural Society at 10 a.m. on Saturday, March 15, at the Hyattsville Municipal Center.
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Miss Floribunda writes about gardening for the Life & Times. You may email her at Floribundav@gmail.com.
