Wild edibles and life cycle
Biennials such as burdock are best harvested in their first year
Suppose you have decided to harvest wild burdock root for a meal or to make an herbal medicine. It will help you to know that burdock is a biennial.
This term refers to a plant with a two-year life cycle, since the first-year burdock plant, with its big, low leaves, looks very different from the second-year version, which features a large, branching stalk with smaller, hand-sized leaves and thistle-like purple flowers and/or prickly, round seed pods.
Most field guides focus on the flowers and will not show you the first-year plant’s striking leaves, which can be as long as your arm and half that width, with wavy edges and whitish fur on the underside. The first-year leaves are known as “basal” leaves, since they form a “base” of leaves, growing straight out of the ground, not on branching stems. Yet this rosette of basal leaves is the form you would seek if you wanted to dig a burdock root for eating. An understanding of the biennial life cycle will show you why.
The second-year biennial, with all its energy invested in producing flowers and seed, its last act before death, has no nutrients left in its root. If you dug the root of a burdock that was flowering or going to seed, you would find a tough, fibrous, inedible substance. The sweetish, white-fleshed root of a first-year burdock is what you are looking for. However, even in the first year, there are better times than others to harvest.
In the first summer of its life, as the young plant is growing, the minerals and water gleaned from the soil by the roots are being sent up to the leaves so they can put on bulk and manufacture more glucose through photosynthesis. Glucose is heading down to the roots to combine with some of the minerals and increase the size of the root. The regular exchange of nutrients makes for a decent-tasting root. But after a good hard frost, the leaves begin to die back, and any nutrients produced or taken in by the plant are stored in the root. Fall is the time when the roots are sweetest and packed with the most vitamins and minerals.
Early spring, as the second-year leaves are beginning to push out of the ground, is another good time to harvest, before most of the stored energy of the root has gone into the growing leaves.
