Prune olive trees yearly in spring or summer when the tree is flowering. As the University of California Cooperative Extension points out, this will allow you to ensure that enough fruit will be produced after cuts are made.
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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.