September 25, 2010

1 - You can rototill lawn clippings into the garden in the fall to decompose through the winter if they are herbicide free.

Yard and Garden - September 25, 2010


Should I till lawn grass clippings into my vegetable garden now (this fall). I have more than I can compost?

- RJ

Moriarty, NM


The answer is yes, you can put compostable material (especially non-woody material that will not leave a residue in the way of tilling next year) into the garden now. This includes kitchen wastes (except perhaps corn cobs and other hard things, but even these can be fine if cut into small pieces to decompose more rapidly). These organic materials will decompose during the winter in the garden. After the ground freezes, the decomposition process will stop, but grass clippings decompose rapidly and in the process generate heat to allow composting to continue a little longer.

However, a warning regarding lawn clippings is that you should be careful if you have used any weed killer products on the lawn this year. Which product did you use (broadleaf herbicide, grass herbicide, preemergent herbicide and how long ago did you use it? If it was long enough ago, the products should have mostly decomposed (depending on the half-life of the product and time of application). Also, if you will grow corn in the area where you put clipping where you used a broadleaf herbicide there is no problem, same for grass herbicide on grass put where broadleaf plants (beans, squash, chiles, tomatoes, etc.)will be grown. Lawn clippings on which you used preemergent herbicide applied before mid-July should have no negative effect (I am being very conservative about this answer). If you used the products according to the label directions, you should be OK with the timing and placements I mentioned above. Even during the growing season, grass clippings can be put into the garden as mulch if you wish, but the caution about herbicides becomes especially important then. Apply fresh grass clippings (without herbicide residue) in thin layers, well spread, to prevent them from generating heat and composting next to the plants in the garden - this heat could damage the plants.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email:, office: 505-865-7340, ext. 113.


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