contaminated soil from weed killer

Question

Should I dig up the soil? Should I just turn it over for the winter and then replace with new soil in spring? [Lawn care company sprayed on a windy day at apartment building next door and killed 2 Forsythia bushes and all my Mayapple groundcover.]

Answer 1

It's unfortunate that the lawn care company damaged your garden. Would it be possible to contact the lawn care company and find out what chemical(s) they used? The reason is that some herbicides (weed killers) break down in just a few weeks, while others can remain in soil for years. Once you know the chemical name, you can look up product information on how long it takes to breaks down. If it turns out to be a persistent one, you will probably need to replace with new soil.

This advice is aimed toward farmers, but should apply to gardeners as well:

http://oregonstate.edu/dept/nursery-weeds/feature_articles/herbicide_carryover/herbicide_carryover.htm

To see if the soil is safe next summer, you could try the "bioassay" technique they suggest.