How to dig up burdock roots! Burdock is a biennial with an edible taproot that can be 2 to 3 feet long. The lower part of the root is more tender, but it's often very difficult to dig to and not worth the effort when you can quickly harvest the top 8 to 12 inches. Burdock roots are best dug in early spring before the two year old plants start flowering, or in late fall after the first year plants have become established. Using a long bladed shovel, dig around the perimeter to loosen the soil, an