The only truly effective defense for a gardener is pre-planting elimination. Before planting the lawn or restocking the flowerbed, keep the soil bare and moist for three to four months. Spray the area with herbicide every three weeks until weeds germinate. This method not only kills the seeds in the soil, but also the weeds whose seeds managed to escape the spraying. Fumigation is another option, particularly for those about to plant a new lawn.
Fumigation involves the use of gasses over a three-week period to treat weeds.
Fumigation is expensive and best performed by professionals who know how to work with the highly toxic gas methyl bromide. If evacuating your plants to allow their bed to lie dormant for three or four months is not part of your gardening logistics plan, then the battle must be fought after weeds have already rooted. Aside from laborious plucking, the only post-emergence weed control method involves herbicides. Herbicides are categorized as systemic or contact chemicals. Systemic herbicides kills every part of the weed from the roots to the tips of the leaves.