TWIGAMETHALIN is a broad-spectrum selective residual herbicide for the control of many annual grasses and annual broad-leaved weeds in wheat, rice and barley. It is absorbed through the roots of the weeds as they germinate/emerge and the leaves of weeds that are already present. The affected plant dies shortly after germination or following emergence from the soil. It works by inhibiting cell division and cell multiplication. Gramoxone kills all green vegetation by contact action. It does not affect the brown mature back of trees.