By fall, the once-edible stalks of Common Burdock (Arctium minus) have flowered and gone to seed, but one or more young plants sporting basal rosettes of leaves are often visible nearby. If you're after the edible taproot of Common Burdock, look for these stalkless plants.
Depending on the size of the plant, soil conditions, and quality of your digging implement, unearthing a taproot can be quick and easy or rather involved. To make things easy, I used a metal shovel and selected small rosettes (indicating smaller taproots) growing in loose soil. Common Burdock taproots can be cooked (boiled, roasted or thinly sliced and sautéed) and eaten or prepared into medicine. Since I already had a jar of tincture, I ended up eating these.
Note: The related Great Burdock (A. lappa) has a similarly edible/medicinal taproot, which can be much larger, and significantly more work to unearth.