As you know from my previous post, the Spokane, Wash. area has been dealing with horrible wildfires. I’ve recently been asked if wildfire ash can adversely affect garden produce or the soil.
I did a bit of research to find out the answers to that and here’s what I’ve learned:
Is garden produce safe to eat?
According to Oregon State University’s Extension, “The produce was exposed to smoke and may have ash on it. The smoke and ash won’t be able to necessarily penetrate deep into the fruit or vegetable and so rinsing well should remove any residues. Rinse the produce off outside (with a hose or watering can) and then give a second or third rinse in the sink indoors. Peeling (for example removing apple or tomato skins) and removing the outer leaves of leafy greens will also reduce your risk.”
They go on to say “Again, use your best judgment in all of this. If your garden has a heavy layer of ash, was located near a structure fire (which creates different toxins than a forest fire), or you are at all uncomfortable — when it doubt, throw it out (into the compost pile).”
Source, and for more information: Is it safe to eat my garden produce affected by wildfires? (https://extension.oregonstate.edu/ask-extension/featured/it-safe-eat-my-garden-produce-affected-wildfires)
The University of California Agriculture & Natural Resources suggests that you rinse the produce from your garden. “Discard produce that is burnt or coated in soot, ash, or fire suppression chemicals. Discard the outer leaves of leafy greens which have the most ash and soil particles attached.
After The Fire: Home Garden and Fruit Tree Safety
UC ANR Fire Network
- Pre-rinse produce outside with a gentle spray or dip in potable water to remove soil, grit, ash, and
other particulate matter (Figure 4). - Rinse produce inside in cool, running water. Use a produce brush on hard, bumpy surfaces, and
hands and fingers on smooth or delicate surfaces. Peel fruits and vegetables to remove outer layers.
While urban wildfires can expose people to hazards through contact with contaminated air, water, food, and
soils, wildfires rarely permanently damage gardens, orchards, and agricultural systems. Because
increasing concentrations of potentially harmful particulate matter in soils may not be immediately obvious, lab
testing is recommended. Gardening has many benefits, including stress relief, and eating nutritious foods can
serve as a protective factor from wildfire smoke and ash.13 Considering your personal health factors and
your garden’s proximity to burned areas will help you decide whether to use your garden produce.”
Source, and for more information: After The Fire: Home Garden and Fruit Tree Safety https://ucanr.edu/sites/default/files/2025-08/UCANRFireNetwork-AfterTheFire-HomeGardenFruitTrees.pdf
I did notice that multiple sources recommended washing the produce twice, once outside and again indoors.
How Ash Affects Soils
According to the research I did, heavy layers of wildfire ash can adversely affect how water moves through the soil. For example, the soil might not absorb moisture as well as it used to.
Ash can also make the soil’s pH more alkaline. If your garden received a lot of ash, it would be worthwhile to do a soil pH test so see if you might need to add certain soil amendments.
To get recommendations on those, contact your local Master Gardener program. Look up the Spokane County program at this link. Do you live elsewhere but your don’t know how to contact your program? Do a web search on “Master Gardeners” plus the name of your county and state or Canadian province.