Pick a location in your garden with access to as much sunlight as possible. The soil should be rich, with enough sand for good drainage and as loose as possible.
Break up the soil where you will be planting the burdock. Dig about two feet down with the shovel and turn over the soil.
Break apart the chunks of the soil to loosen it and look for pebbles andl rocks. Pull all of the rocks out of the soil. Loose soil free of stones will encourage longer burdock roots.
Plant burdock seeds about 1/4 inch deep. Watch their growth until the seedlings are several inches tall. Pull out some of the seedlings so that the remaining plants are spaced three inches apart. The spacing will allow room for the roots to develop.
Fertilize the soil once per month. These nutrients will be soaked up by the roots directly. Add a general-purpose fertilizer that encourages root growth for best results.
Trim some of the leaves as the plants grow. This will encourage more energy to be spent on the forming of long roots.