Corn is a type of grass, so use a broadleaf herbicide to control weeds around sweet corn without affecting it. For grass weeds, consult with your local extension office for suggestions. Weed killers are divided into three general types according to the plants it affects: grasses, broadleaf and broad spectrum. Broad spectrum kills all types of plants, so should not be used around corn plants.
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Marie Notnats enjoys learning about new topics and teaching people new skills. She has been writing professionally since 2008. She is a professional horticulturist with a Bachelor of Science degree in horticulture from Brigham Young University. She writes for About.com, Examiner.com, eHow, and assorted gardening blogs.