A proprietary use patent is granted for seventeen years to the company that first develops a herbicide. All of the active ingredients in the herbicides that are commonly used on vegetables are now off patent. Most have been off patent for more than 20 years. Some companies have developed proprietary formulations that contain off patent active ingredients. Some examples of these are Prowl H2O, GoalTender, Select Max and Dacthal Flowable. Please click on the following link   to see a list of these herbicides, the year of first registration and the original registrant for lettuce, cole crops and melons.