Have you noticed trees and shrubs changing color already? My burning bush is starting to turn red. I have seen poplars and ashes yellowing and maples reddening.
Normally fall colors are triggered by changes in daylength and temperature. With less sun and cooler temperatures, chlorophyll, which gives plants their green color, breaks down. As the green color declines and eventually disappears, the yellow xanthophyll pigments, the orange carotenoid pigments, and red anthocyanin pigments come through.
With the intense smoke recently, the days have had less sunlight and the temperatures have been lower. Add a drought into the mix and plants are confused. A false autumn has been initiated.
Although some plants need fire for seed dispersal and germination, in general, “smoke and ash are detrimental to plants” (https://botanicalgarden.berkeley.edu/glad-you-asked/amoke-ash-plants). Some researchers report chemical compounds in smoke reduce photosynthesis, the process by which plants transform the energy of the sun into chemical energy for growth.
“Short-term exposure to smoke (as little as 20 minutes) has been reported to reduce photosynthesis by as much as 50%” (2010. W.J. Calder, et al. International Journal of Forestry Research).
Others suggest that wildfire smoke diffuses sunlight allowing light to reach all leaves of a plant instead only those at the top and increases photosynthetic efficiency (https://eos.org/research-spotlights/wildfire-smoke-boosts-photosynthetic-efficiency). Reduced photosynthesis can reduce plant growth, fruit production and also slow fruit ripening. Increasing photosynthesis efficiency benefits plant growth.
Long-term exposure to smoke can affect the taste of fruit and vegetables according to the Berkeley Botanic Garden. I wonder what wines will taste like in the years to come after multiple years of excessive smoke in grape-producing areas. Gives the description “smoky” a whole new meaning.
On a happier note, ash is actually organic matter floating in the air and contains necessary plant nutrients such as calcium, magnesium and potassium. The ash can act as a fertilizer as long as it doesn’t smother plants (Berkeley Botanic Garden).
Although I have been mostly avoiding going outside, occasionally I put on my N95 mask (a cloth mask doesn’t cut it), go out and hose off as many plants as I can to get the ash off.
All this dismal haze feels like some of our gray winter days. But, at least in winter I can put on a coat and gloves and go for a walk! Being out when the smoke stings the back of my throat is unhealthy. I miss my gardening and yardwork!
JoAnne Skelly is associate professor & extension educator emerita of the University of Nevada Cooperative Extension. Email her at skellyj@unr.edu
