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“Light-winged smoke, Icarian bird ... by night star-veiling, and by day darkening the light and blotting out the sun…” — Henry David Thoreau, "Smoke," 1843 The hazy smoke from Canyonville and Northern California wildfires has seemed anything but light-winged these past several days, instead lingering over the valley and creating unhealthful breathing conditions for everyone, including gardeners. We have the option of staying indoors, but how are our outdoor plants faring in the smoke? Similar to humans, plants are affected by fine particles in smoke that consist of ash, partially consumed fuel, water droplets and hundreds of chemical compounds, including carbon monoxide, carbon dioxide, hydrocarbons, and small amounts of nitrogen oxide. These particles can clog the plant’s stomata, tiny pores that enable the plant to absorb carbon dioxide and other gases from the atmosphere and release oxygen. Prolonged blockage can suffocate the plant. In addition, studies have shown that even short-term exposure to smoke destroys chlorophyll in plants and, thus, reduces their ability to carry out photosynthesis by as much as 50 percent. The result is oxygen-deprived plants that are stressed, weakened, and may look wilted and washed out. Once the plant has switched to survival mode, fruiting and ripening slows down, which may be why my friend said her corn crop yield was “puny” two years ago when smoke hung in the valley for several weeks. Prolonged exposure to smoke may also affect the taste of garden produce. If all this sounds depressing, then know there are actually some benefits to plants associated with smoke. Smoke reduces the intensity of direct sunlight, which helps to prevent heat stress and sunscald. Smoke diffuses sunlight, and so light reaches plants from different directions. This means lower leaves may capture more sunlight than they would under normal conditions, and are therefore better able to produce food for the plant. Smoke may also provide an advantage to our garden plants by inhibiting fungal diseases and insect activity. In fact, plants have been adapting to wildfires and smoke for the past 350 million years. There is evidence that plants use smoke as an environmental cue to initiate defense mechanisms that help them to continue growing and reproducing. For example, smoke activates seed germination in some plant species. The best news is that plants have evolved remarkable resiliency. Once the air clears, our garden vegetation will resume its normal processes, just as we return to our gardening routines. We can assist our plants by spraying the leaves and fruit gently with water and applying fertilizer to promote healthy roots and foliage. Thoreau called smoke an “Icarian bird” because it reminded him of Icarus, the character in Greek mythology who flew too close to the sun and plunged into the sea. Today, the smoke has obscured the sun but, like Icarus with his wings made of feathers and wax, it won’t last. In the meantime, here’s how Thoreau wished the smoke away: “Go thou my incense upward from this hearth, and ask the gods to pardon this clear flame.” Rhonda Nowak is a Jackson County Master Gardener and teaches writing at Rogue Community College. Email her at [email protected].