A rotary tiller has the ability to cut through some roots. The amount will depend on the blade size and tiller depth and root type, size and depth. Larger roots may cause the tiller to jump, according to the LSU Extension, which is a dangerous situation.
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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.