Cutleaf teasel (Dipsacus laciniatus L.) is an invasive plant that is spreading through natural and disturbed areas. Teasel grows for two or more years as a rosette which stays green late in the growing season and begins growth earlier in spring than its native competitors. The purpose of this study was to find a time both seasonally and in cutleaf teasel’s life history when herbicides could be applied to decrease teasel with the least impact on the surrounding vegetation. We tested the effects of three different herbicides (glyphosate (Round-UpTM), triclopyr amine (GarlonTM), and clopyralid (LontrelTM)) on cut and uncut teasel at three different times of the year (July and October 2005, and April 2006) near Clinton Lake in Dewitt Co. Illinois. Photosynthetic measurements were taken before application to determine teasel’s susceptibility to the herbicides, and we harvested seed heads and rosettes in late October 2006. Results indicated teasel was photosynthetically active at all three application times. Cutting before herbicide application had no significant effect on the number of seeds produced or the dry weight of the rosettes. Herbicide treatment in April significantly reduced the amount of seeds produced, but there were no significant differences among the three herbicides. Clopyralid application in April significantly reduced rosette biomass, but none of the herbicides significantly affected rosette biomass at the other two times. Our studies suggest herbicide application early in the growing season may be beneficial in controlling the spread of teasel, and that mowing at the time of spraying will not increase effectiveness of the herbicide.