Grazon herbicide in Straw. Is it used in Oregon?

Asked January 20, 2021, 1:03 PM EST

I've seen gardeners show their gardens fail because of the Grazon herbicide that is used in growing grass. That the herbicide is persistent and can poison your ground for broadleaf plants. Is straw sold and/or grown in Oregon a risk?

Benton County Oregon

1 Response

Greetings,

Home gardeners growing veggies, berries and some flowers will want to watch out for composts and mulches that may contain picloram, clopyralid, and aminopyralid because they can remain active in hay, grass clippings, piles of manure and compost for an unusually long time.

The best solution is to get compost or mulch from a known source and inquire about what went into it. But gardeners can do a clever test by growing some beans, peas or other sensitive plants in the compost. Healthy plants = compost without residual herbicides. This article has full details:

https://extension.oregonstate.edu/crop-production/soil/herbicide-carryover-hay-manure-compost-grass-clippings

This article has more details:

"If you want to use hay or grass clippings as mulch or in your compost pile, find out what, if any, herbicides were used on the field or turf area. Be particularly careful about obtaining grass clippings from golf courses and other commercial turf fields where these herbicides are commonly used. Most homeowners do not use these herbicides because they are not labeled for use on residential lawns. Be careful about obtaining hay or grass clippings from sites where herbicides of concern may be commonly used. For instance, clopyralid- containing products have not been registered for use in residential lawns since 2002, so if pesticide applicators have followed label directions, clippings from residential lawns should not present a problem to use as mulch around vegetables and ornamentals. As previously mentioned, the safest practice in residential lawns is to return grass clippings to the lawn. If you find yourself with contaminated hay or grass clippings, spread them on non-sensitive, non-food crop areas, burn them, or arrange to have them disposed of safely. If the hay or grass clippings have already been applied to the field or garden, remove them if possible, till the soil (multiple times will enhance degradation), sow a non-sensitive cover crop, and let it grow for a year or two to help the herbicide break down. Read more at: https://lee.ces.ncsu.edu/2016/03/herbicide-carryover-in-hay-manure-compost-and-grass-clippings/"

So, no easy answers but good food for thought. I do believe that customers asking knowledgeable questions of suppliers about their source and what they do to prevent contamination could help.

If you have questions about specific pesticides in mulch and implications for human health, National Pesticide Information Center’s hotline is a wonderful free resource. Find them here: http://npic.orst.edu/

I hope this helps you figure out next steps with your garden. If we can help further please reach out and thanks for contacting Master Gardener volunteers.