Burdock is a biennial plant that reaches a mature height of 7 feet. The small purple flowers begin to bloom in July and continue until the first frost. Control or extinguish the plant by either cultivation or applying herbicide. In both instances, the plant must be extinguished prior to the flower heads producing seeds. One burdock plant can produce up to 15,000 seeds.
Dig the plants from the ground using a shovel. Remove as much of the root as possible. Larger roots left in the ground will sprout new upper leaves. Dispose of the plants where they cannot grow.
Mow smaller plants to keep them from creating flower heads. Burdock plants that cannot produce flowers will not produce seeds.
Spray the plants with an herbicide such as glyphosate or 2,4-D. Mix the herbicide according to label directions. Apply the chemical directly on the leaves of the plant prior to the bloom stage of the flowers.
Inspect the herbicide-treated plants two weeks after spraying. Re-treat with the herbicide if any portion of the burdock plant shows signs of green.