As the smoke dims the sunlight and casts an orange glow across the sky, many of us might wonder how this change affects our gardens. The good news is that, even though there is thick smoke in many parts of the country, not accustomed to it, reduces sunlight, our plants are more resilient than we think.

Plants “breathe” through tiny openings on their leaves called stomata during photosynthesis. This is where carbon dioxide in the air is exchanged for oxygen, and where water vapor is released. (It’s also why massive, industrial cornfields can impact the weather, but that’s another story.) Wildfire smoke can reduce the amount of sunlight that reaches plants and slow this process, especially in sun-loving plants. On the flip side, the diffuse light actually reaches the understory better within the tree canopy, so it can be a bit of a benefit for those plants. The bottom line is that unless the smoke continues for weeks, there are typically no long-lasting effects on this important process.

Smoke Not a Problem for Vegetables

I’m visiting Ohio at the moment, and while there are no active fires in the state, the smoke is pouring down from conflagrations in Canada. Around here, it is hot, but after frequent rains, everything is still very lush. That’s not always the case, though, when wildfires are a concern, because hot, dry conditions often go hand in hand with them. Stressed plants are more prone to diseases and pest infestations. When plants are already struggling with drought and heat, it’s important to water consistently and take measures to reduce evaporation, such as mulching around the plants to keep the roots cool.

Watching the news, I see parts of Michigan where ash is falling on homes and landscapes. For the most part, you don’t need to panic. If it’s light ash, just brush it off before the house and, of course, wash thoroughly. One caveat, though, is that if you are near homes or an industrial area that is on fire, you should probably avoid eating anything covered in ash, as it could contain hazardous contaminants.

If you do have ash on your plants, you might be tempted to hose it off immediately and repeatedly, but unless it is a very heavy coating, it’s wiser to wait and, ideally, let the wind take some of it away before you hose down the rest. A little ash won’t disrupt photosynthesis very badly for a short amount of time, but if the smoke in the ash persists, you will want to clean up your plants.

I should also note that even though our gardens can withstand smoky skies in the short term, it’s important for people to protect themselves, particularly if they have respiratory issues, such as asthma. I would say to keep an eye on the news to see what the levels are, but truthfully, you can look outside and know for yourself. If you smell smoke and it bothers your eyes or make your nose itch, don’t go outside for extended periods of time. It doesn’t matter if you can’t get all the weeds right now. Let the smoke pass, and then tackle your garden projects.