These include common chickweed, henbit, most mustards, downy brome and cheat. The growing points on young annual grasses are at or just below the soil surface while the growing points on annual broadleaves are elevated above the soil surface. Thus, annual grasses are more difficult to control with flaming or foliar treatments of contact or apoplastically translocated herbicides than broadleaved plants are because of their growing points are more protected. Biennial weeds germinate and form a rosette the first year are vernalized by cold during the winter and then they send up a flowering stalk and die the second year. They do not persist in management systems that are severely disturbed seasonally.
Biennials are most susceptible to herbicides when in the rosette stage.
Many are held in check by close mowing. Mowing has the greatest impact when done just as the first flowers open. Bull thistle, musk thistle, and wild carrot are the most widespread problem biennials in Indiana. Simple perennials survive best in perennial crops or undisturbed areas. Those with leaves near the ground can survive mowing.