This time lapse video shows Palmer amaranth and waterhemp plant growth from July 30 to August 27th 2015 in northwest Indiana. The two plants in the vidoe begin at approximately 1 inch in height. During the first week of growth both plants add multiple leaf nodes and reach 2 to 3 inches in height. During the 2nd week the plants begin to grow rapidly and reach 6 to 8 inches in height by the end of the 2nd week. At this time the plants are at the maximum growth stage for effective control with post emergence herbicide applications. Both plants then continue rapid upward growth of at least 1 inch per day and quickly grow out of the optimal range for herbicide application.
The overall goal of this video is to show the rapid growth of these two weed species, and to emphasize that the window for an effective postemergence herbicide application occurs over a very short period. To achieve optimal herbicide efficacy an application would have been needed by Aug 9th or the 1.5 week mark. It took only four days for the plants to reach the maximum height on Aug 13th or the 2 week mark. This rapid growth makes these two pigweed species extremely difficult to manage, especially when solely relying on postemergence applications.