Bull thistle, tall thistle, musk thistle, and wild carrot are the most widespread problem biennials in Indiana. Others include wild parsnip, evening primrose and common mullein. Once rosettes become well established, shallow tillage and foliar applied herbicides which translocate symplastically should provide control. Seed production of many biennials is suppressed by close mowing. Mowing has the greatest impact when done just as the first flowers open.
Simple perennials survive best in perennial crops or undisturbed areas.
Simple perennials that generate shoots from crowns under the soil surface tolerate single treatments of shallow tillage, hoeing, and contact herbicides as well as mowing. Dandelion, curly dock and pokeweed probably cause the most problems in Indiana. We frequently receive requests for control of alfalfa which is also a simple perennial. Repeated tillage three or more inches deep and symplastically translocated herbicides provide effective control. Creeping perennials reproduce by seeds and vegetative structures.