Ask the Ethicurean: What will vog do to my veggies?

We’re reviving the Ask the Ethicurean column by plucking a recent question from the comments section. Send your burning questions about SOLE food to and we’ll use our collective brain, contact list, and PhD in Googling to guess at the answer for you.

Aloha, I too have an organic garden to supplement my pantry…However in recent years the volcano has been emitting VOG. Can someone tell me just how this is affecting the “organic” quality of my crops? Yes sulfur is organic…but something isn’t sitting right with me…there’s a white coating on the leaves and I wonder if anything is really safe to eat…Does anyone have advice for growing under such circumstances?
—Amy in Hawaii

Yuck! Poor you. We assume you’re talking about Hawaii’s Kïlauea volcano, the most active volcano now on Earth, which has been erupting continually since 1983. Vog is icky stuff, the same gas as produced from burning fossil fuels — just like smog, only from a volcano. Vog and smog are both sulfur dioxide, which reacts with sunlight and other atmospheric gases to form a haze, or with water to produce acid rain. As the sulfuric acid builds up, it becomes lethal to plants and is decimating many Big Island crops, reports the San Francisco Chronicle.

Researchers with the University of Hawai’i's Department of Plant and Environmental Protection Sciences have published a booklet, “Volcanic Emissions Injury to Plant Foliage,” available as a PDF download, that describes vog damage, which plants are most sensitive (edible ones include broccoli, daikon, green onion, lettuce, tomato, and watercress), and how to protect both them and the soil, which will become overly acidic and experience toxic levels of heavy metals. The researchers suggest that gardeners and farmers:

  • Flush leaves and flowers with fresh water after their exposure to acid rain or ash.
  • Treat acidified irrigation water to raise the pH.
  • Grow plants under cover, in greenhouses where possible.
  • Grow plants that are SO 2-resistant, if possible.
  • Selectively and temporarily cover valuable plants with fabric or plastic.
  • As a possible preventative measure, spray plants with anti-transpirant products to close their stomata or with bicarbonate solution to neutralize acidity (still being researched by the University of Hawai‘i).

If all you have is a white coating on the leaves, rather than withered yellow or brown leaves or other visible signs of a sick plant, that’s probably just volcanic ash. The UH pamphlet says ash does not damage plants directly unless it is not removed and starts to block sunlight, or combines with moisture and becomes acidic. Ash should probably “not be eaten. It can and should be washed from plant foliage and fruits with water,” say the researchers.

However, if your Victory Garden was in fact vog-damaged rather than just ash-covered, whether it could be still considered “organic” in spirit, the sad fact is probably yes. Sulfur dioxide is not allowed as an additive in certified organic winemaking (where its main function is to prevent browning), but it is in other organic food processing; see National Organic Program rules (PDF). It is one of those chemicals toxic in high doses but that the govenrment regards as “generally recognized as safe.” (Fun fact: sulfur dioxide can be used as smoke bombs for underground rodent control in organic crops.)

Unfortunately, from what we have read, your real health risk lies in the high levels of sulfur dioxide you are likely inhaling, rather than ingesting. We’d stay inside and limit our gardening for a variety of reasons.

Photo of Kïlauea vent from the USGS Hawaiian volcano website

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