Common name: Burdock

Burdock is a biennial herb native to Asia and India, where it is cultivated as both a vegetable and medicinal plant. Plants grow to between 1 and 2.5 m (3 to 8 ft) tall, reaching their maximum height in the second year, at which time they flower and produce seed.

The leaves are large, heart-shaped, green with a rough texture, and covered in soft white hairs. The thistle-like flowers are purple and bloom once only when the plants are about two years old.

Use

Burdock is cultivated commercially in China, Japan and Southeast Asia for its roots, which are consumed mainly as a cooked vegetable, and for its seed which are used medicinally. The plant develops a long tap-root that has the shape of a thin carrot, 50 cm (1.6 ft) or more in length.

The brown skin is easily peeled or scrubbed off to expose the white flesh underneath, which is then cooked similarly to other root vegetables, either baked, fried or steamed. The roots are not peeled until they are used or are peeled and covered with water to stop the white flesh from oxidising or discolouring on exposure to air.

Health use

The seed and dry root are used as a detoxifying and blood purifying herb in traditional Chinese medicine to cleanse the body of toxins, including heavy metals. The seed reportedly contains 14 to 20% of an oil used in various medicinal preparations, particularly in treating skin disorders. The roots are rich in inulin, a carbohydrate suitable for diabetics' consumption. They are also rich in calcium, iron, and potassium.

Climate

Although native to warm temperate regions, it grows well in moderately humid subtropical climates, generally areas with annual lows of 12 to 19°C, annual highs of 20 to 30°C, annual rainfall of 1000 to 2300 mm and a dry season of 4 months or less.

Growing

Burdock is propagated using pre-soaked seed sown either in autumn or winter in warm climates. 

It performs best on deep, loose, free-draining loam and sandy loam soils with a slightly acid to slightly alkaline pH, in the range of 6.0 to 7.5, and on sites with full to partial sun exposure. Shallow, rocky, or poorly-drained soils are not suitable for growing Burdock.

The long roots are harvested when the plants are 5 to 8 months old. Plants cultivated for their seed are left to grow into their second year when they flower and set seed.

Problem features

The seed are encased in burrs that attach to animal fur, clothes and similar material brushed against the plant, enabling the seed to be carried and dispersed afar. Burdock has become naturalised in many parts of the world and is listed as a serious or noxious weed in more than one reference publication. The airborne burr fragments can also be a skin, respiratory and eye irritant to humans and domestic animals.