HOME & GARDEN
Wildfire smoke can impact your home garden
Mike Hogan
Special to The Columbus Dispatch
Aug. 8, 2026, 6:01 a.m. ET
- Smoke from Canadian wildfires has recently impacted central Ohio, raising concerns for gardeners.
- Wildfire smoke can scatter sunlight, which may surprisingly increase plant photosynthesis.
- However, smoke also generates ground-level ozone, which can damage plant leaves and reduce crop growth.
The smoke from Canadian wildfires that moved through central Ohio recently caused some gardeners and vegetable growers to question the potential effects of smoke on vegetable crops. While the smoke was visible in central Ohio, it was more pronounced in northern Ohio locations
I was on a boat on Lake Erie, close to Canada’s Pelee Island, and the smoke obscured the view of the Lake Erie islands for several miles
While the presence of wildfire smoke in the atmosphere in Ohio has not historically been a common occurrence, the increased incidence of wildfires throughout the United States and changing weather patterns may cause it to become more common in the future
Wildfire smoke and light levels
Wildfire smoke aerosols create a shadier atmosphere, so you might think that less sunlight is reaching the plants in your garden. However, research at the University of Minnesota found that wildfire smoke creates more diffuse radiation, meaning that light is more scattered throughout the atmosphere
Plants can use the diffused light associated with smoky conditions more efficiently than direct sunlight, and so photosynthesis can actually increase under these conditions. This potential benefit, however, may be negated by the impacts of wildfire pollutants such as ozone
Increased ground-level ozone
Smoke from fires generate ozone and other aerosols at ground level. Plant cells called stomata on the surface of plant leaves exchange gases such as carbon dioxide and oxygen. When high concentrations of ozone are present in the atmosphere, it can enter plants through the stomata and interfere with photosynthesis, resulting in reduced plant growth and productivity
Researchers in California have found that plants growing hundreds of miles away from actively burning areas can be negatively affected by increased ground levels of ozone. Symptoms of ozone injury can vary by plant family but typically include chlorosis, or yellowing of leaf tissue between leaf veins
Increased levels of ozone can cause bleaching and stippling of leaves, similar to damage commonly caused by flea beetles on eggplant or cucumber. Potato growers in the western United States have experienced leaf loss and misshaped potatoes due to repeated exposure to ozone from wildfires more common in western states
Ash more common close to wildfires
In California and Australia, where wildfires are more common, ash settling directly on crops can create a physical barrier which affects access to light, reducing photosynthesis and plant growth. A few years ago, while visiting my son who lives in northern California, I had to use the windshield wipers to remove ash in order to see through the windshield while driving on the highway
Ash is typically not carried long distances by the wind and is noramaly deposited close to wildfires. Grape growers in both California and Australia have had to discard grapes after wildfires due to flavor changes caused by ash covering the porous skin of the grapes
Human health and safety
While the impact of wildfire smoke on vegetable crops can be variable, the impacts on humans are more clear. Symptoms of smoke exposure include burning eyes, a runny nose, chest pain, fatigue, coughing, difficulty breathing and a rapid heartbeat
In states where extended periods of smoke are more common, health professionals have developed air-quality safety guidelines for farmers and agricultural workers. These guidelines serve as a basis for determining when it is safe for humans to work when the threat of smoke exposure is present
Mike Hogan is Extension Educator, Agriculture & Natural Reon. He can be reached at hogan.1@osu.edu
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