by Estella   Heitman Oxeye Daisy (Chrysanthemum leucanthemum)      Every gardening enthusiast has a "pet peeve" or two.   For this gardener, it is the Oxeye Daisy.   This daisy is native to Europe and was introduced to America intentionally as an ornamental and accidentally as a contaminant of imported hay and grain seeds.   It has spread to virtually every state, and in Colorado it is now included on the B List of Noxious Weeds.    Noxious weeds are not just plants out of place; they are non-native plants that are displacing native vegetation and disrupting ecosystems.   List B plants are those for which The Colorado Commissioner of Agriculture, the Colorado Noxious Weed Advisory Committee & local governments are developing and implementing plans to stop the spread of the species.   The greatest impact of the oxeye daisy is on forage production of infested pastures and meadows.   Cattle avoid grazing oxeye daisy.   Dense stands of oxeye daisy decrease plant diversity.