How do I control weeds in my lawn? Olympia & DuPont Lawn Care Experts Most broadleaf weeds in lawns are controlled with a selective herbicide.  Selective herbicide kills weeds by causing the cells in the plant tissue to divide and grow without stopping.  With the proper rate and timing, selective herbicide only effects dicotyledons, also known as dicots, seeds that have 2 embryonic leaves like broadleaf weeds.  It has no […]