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Polluted Compost

Published in the six Nashoba Publishing papers on Friday, 8 Febrary 2002

You start some tomatoes in the house, and they look good when you set them out in the garden. Four weeks later, you notice the leaves are shaped funny, and spaced a bit far apart; the stems are twisting. Has it been too cold, you ask yourself, did you put too much nitrogen on them, what can you do?

Probably you would never even suspect the compost you put on them, especially if you made it yourself organically. But an herbicide called Clopyralid (pronounced Clo-PEER-uh-lid) is showing up in "organic" compost, because it is so resistant to breaking down. It survives the high heat of even the best composting processes; it even passes through the digestive systems of animals and remains potent in their manure. It takes months or years to degrade, and remains damaging in extremely low concentrations.

Clopyralid herbicides -- including Stinger, Confront, Reclaim, and dozens more -- are effective at killing broadleaf weeds like dandelions, clover and thistle. So far, studies indicate "low" toxicity to humans. However these products are quite harmful to tomatoes, potatoes, peppers, sunflowers, asters, carrots, lettuce, petunias, violets, peas and beans -- among other garden plants. It mimics plant auxins, which are growth regulators. Among other effects, it prevents fruit set.

Clopyralid products are marketed for application to lawns, turf, pasture, rangeland, forest, and right-of-way; and to crops of cereal grains and sugar beets. Dow Agro Sciences advises users not to compost the plant residues from areas treated. But then what are they supposed to do with it? Many people think composting is the only responsible use of green waste; public landfills increasingly refuse to take it. Dow doesn't say what to do with manure from animals who eat treated plants, either.

Seattle, where the problem was first reported, is hard-hit. The Spokane Regional Compost Facility has 25,500 cubic yards of clopyralid-contaminated compost left from the year 2000 alone. It has cost Washington State University over $250,000 from loss of revenue, claims, bioassay and analytical testing, and additional labor. Tests in California and Pennsylvania also show compost contamination.

Is it in compost from suppliers around here? Apparently no one is testing for it yet. When I made several calls, most people had never heard of it.

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© Copyright 2002 Catherine Holmes Clark