Clopyralid contamination of greenhouse vegetable garden

Asked May 10, 2019, 12:31 PM EDT

We removed all existing soil, installed a gravel base for improved drainage, and replaced all soil in our greenhouse. The new soil was a composting planting mix ideal for organic gardening purchased from a local Portland Company. We planted salad greens (lettuces, mustard greens, kale, chard, arugula, radicchio), peas, beans and tomatoes. The salad greens were unaffected. The tomatoes, beans and peas developed twisted stems, cupped leaves and failed to thrive. Portland Nursery examined the planting material and attributed the cause as Clopyralid toxicity, most likely introduced by contaminated composting material in the planting mix. All affected plants were removed. The root systems were withering. Clopyralid soil contamination can persist for several years. Are there safety risks to breathing the air in a greenhouse contaminated by Clopyralid? Is it safe (for humans and our pet turtle) to consume the current crop of non-affected” vegetables (salad greens)? What other vegetables can we plant that will thrive and be safe for consumption? Do you recommend removing the contaminated soil? Abandoning vegetable gardening in the greenhouse? Converting the space to decorative/flowering plants? Converting the planting beds to container vegetable gardening? Could the tools used to plant/manage the existing vegetation introduce Clopyralid contamination to unaffected or new planting sites? Any and all advice, suggestions, help and mentoring would be greatly appreciated. We are at a loss as to the best way to proceed. Respectfully, Barbara Schulman and Ted Giese

Multnomah County Oregon

2 Responses

Thank you for your question, Barbara and Ted. First, as to toxicity to you and pets, here is a through article with the same information as pesticides are required to have on their labels, some of which (application information) is not relevant to you, but does discuss its dangers:

The most thoughtful Extension article I have found to help you remove this contaminant (or find crops that can grow with it which are safe for human consumption) is this one:

What to do with what you have is discussed about 2/3 of the way through the article.

Here is another Extension article which addresses the concerns of the home gardener:

I hope these resources are helpful to you, and you manage to get rid of it as quickly as possible. Good luck!


Another helpful resource for understanding and making decisions in a situation where pesticides end up in an unintended place, is the National Pesticide Information Center. A real person with lots of pesticide experience will talk it through with you, for free. Find them here: