Rural Industries Research & Development Corporation

The New Rural Industries
A handbook for Farmers and Investors

Burdock

Introduction Burdock (Arctium lappa L.) which belongs to the chrysanthemum family (Compositae), is a native of Asia. It has become naturalised in many parts of the world, growing wild throughout Europe and North America where it is used as folk medicine. The Japanese developed it as an edible vegetable when it was introduced into Japan probably a thousand years ago. Today, large areas of burdock are grown only in Japan. Taiwan, China and other South East Asian countries produce some burdock mainly for export to Japan but the import of burdock into Japan at present is small.

Burdock is a biennial plant that is grown and harvested as an annual. Seeds are not produced until the second year. The plant carries its leaves on long stems (approximately 60 cm), originating from the crown. Leaves are large, almost heart-shaped, have a rough texture and are covered with short white hairs, dark green on the top and a paler green underneath with pinkish veins.

The long, tapering tap-root can reach lengths of up to 120 cm. However, roots grown for fresh markets need to be 60_90 cm long and less than 3.5 cm in diameter at the crown. Roots usually have a brown skin with white flesh that oxidises (discolours) quickly when exposed to air.

Burdock is tasty and high in fibre, potassium, calcium, iron, silicon, sulphur, volatile oil and resin as well as containing several antibiotics and it has recognised medicinal properties.

While the consumption of burdock in Japan is stable, the production area is falling (Table 1- not availble in this version). This offers an opportunity for Australia to supply the market, particularly during the period from April to June when fresh burdock is in short supply throughout Japan.

Markets and marketing issues

Japan produces approximately 200,000 t of burdock annually (Table 1- not available in this version), valued at about ¥60 billion at wholesale markets, equivalent to approximately A$800 million. Tokyo's wholesale markets represent some 8% of Japanese sales. Data from 1992 to 1996 show that the average annual throughput for burdock is 15,699 t with an average annual price of ¥299/kg.

The largest volumes of Tokyo markets throughput are from September to December with the lowest wholesale prices, while the higher wholesale prices are from January to June, particularly April, May and June (Table 2 - not availble in this version).

International trade in burdock focuses on Japan, though at present the import of burdock into Japan is negligible. In 1994, Japan imported approximately 421 t of fresh burdock which represented only 0.2% of the domestic throughput. China supplied the greatest amount of 300 t at an averaged landed price of ¥130/kg during the period of January to April. The Philippines also supplied Japanese markets in April and May with 120 t at an average price of ¥153/kg.

Burdock has also been imported into Japan from Taiwan and South Korea. However, information about exports from these countries is not available.

Production requirements

Burdock is a temperate crop that tolerates a wide range of temperatures. It prefers warm, humid climates and grows best at temperatures of 20_30°C. However, it will tolerate much higher temperatures. Leaves die back when frosted, but roots will survive in soil when air temperatures are well below 0°C and roots will re-shoot the following spring.

For quality roots, sandy soil or sandy loam are best. Soil must be deep, with no change in profile to at least 60 cm, and must have good drainage. Soils need to be worked to the full depth of the final root size to prevent forking. Burdock does not like acid soils, and the optimum pH range should be between 6.0 to 7.5.

Burdock for sale as a vegetable is harvested from first-year plants, normally at four or five months' growth if planted in spring, or seven to eight months' growth if planted in autumn.

Varieties (cultivars)

In Japan, burdock is classified into several groups such as Takinogawa, Oura, Hagi and Echizen Shiroguki.

Takinogawa, which is the most common group, has slender, long roots and red petioles. Popular cultivars for this group are Takinogawa, Watanabe wase, Yamada wase, Tohoku riso, Shinden, Nakanomiya and Tokiwa.

Oura, Hagi and Echizen shiroguki have thicker and shorter roots. Cultivars of the Oura group include Oura and Horikawa; the Hagi group include Hagi and Hyakunichishaku and the Echizen Shiroguki group including Shiroguki wase.

There is a very small demand for the burdock leaf. The leaves are taken from small plants two to three months old and grown in shade and at a very high density planting.

Agronomy

Burdock can be sown in spring and autumn. Spring burdock can be sown as soon as soil temperatures are above 10°C. A better establishment will be achieved if planting is delayed until the soil has reached 15°C. Seed germination is very slow, taking 10_14 days for emergence, and can be uneven. In fact, some seeds may lie dormant in the soil and germinate the following autumn. Using primed seed breaks this dormancy and increases both the rate of germination and overall percentage of germinated seed Autumn burdock must be sown late so that plants are still very small when the first frost occurs. Leaves will die back and the plant stops growing until temperatures become warmer in spring. There is a risk of plants bolting (going to seed) in spring if roots are larger than 5 mm diameter before winter. Autumn sowing produces an earlier crop during the following spring/summer.

Before sowing, the soil must be cultivated very deeply — up to 90 cm if possible. Soil must be left in a loose, friable state for roots to penetrate otherwise they will fork and the yield of `A' grade roots will drop dramatically. Up to 80% of roots that fork do so in the top 15 cm due to either a change in soil structure where soil has been shallow cultivated, or if fertiliser with a high N content is banded below the seed line.

A fertiliser with low nitrogen and high phosphate to encourage root growth can be worked into the soil before sowing during deep cultivation. Apply approximately 120 kg/ha P in sandy soils. This rate can be reduced in more fertile, sandy loam or alluvial soils.

Two side dressings of nitrogen and potassium fertiliser should be applied, the first at the two-three leaf stage (approximately 60 kg/ha of elemental N and K) and the second approximately three months after sowing (100 kg/ha of elemental N and K).

Burdock is direct-seeded with 10 cm between plants and approximately 50 cm between rows. Seeds should be sown at about 1_2 cm deep and kept wet until after seedlings become established. Once plants are established, water can be cut back to force roots to seek moisture deeper in the soil profile. It is important not to over-irrigate and saturate the soil profile as excessive moisture can lead to root rot diseases.

Pest and disease control

As burdock is a new crop to Australia, there are no registered chemicals available for weed, pest and disease control. However, burdock is a hardy plant and has few pests or diseases and weeds can be controlled with cultivation and hand chipping.

The slow establishment rate of burdock gives weeds a head start on the crop so it is important to ensure that the site is prepared well in advance of the sowing date. The site should be pre-irrigated and any emerging weeds sprayed off with a knockdown herbicide just before or immediately after sowing. Weeds that establish after the crop has emerged have to be cultivated out or hand chipped. The crop will form a complete canopy approximately eight weeks after germination, which restricts further weed establishment.

A burdock crop grown chemical-free may attract a premium price in Japan where consumers are very health conscious and have shown a willingness to pay extra for `organically clean', healthy, quality foods.

Nematodes (burrowing nematodes) are a major pest and soils should be assessed for nematode populations before sowing. A nematode-repelling crop, such as oats or rape, may be sown as a cover crop during winter and incorporated into the soil before sowing burdock.

In some years, red-legged earth mite can cause damage to young seedlings early in the season. If earth mite are likely to be a problem, planting should be delayed until their activity diminishes.

Powdery mildew may become a problem in mid- to late summer if wet, humid conditions prevail. Symptoms are similar to powdery mildew on cucurbits though the causal agent is different. In most cases the crop will tolerate a mildew infection and it is only in extreme circumstances that crop losses will occur. Wettable sulphur (a natural compound) can be used to control powdery mildew if it is deemed necessary.

Black root is a fungal disease caused by Aphanamyces raphani, which may also cause crop losses. Warm, hot weather and water-logged soil favour its development. The disease is controlled by correct irrigation scheduling, good drainage and crop rotation.

Harvesting and packaging

Spring-sown burdock will be ready for harvesting about 4_5 months after sowing. To obtain the best commercial return, the crop should be harvested when most of the roots are 20_35 mm diameter and at least 70 cm long. If harvest is delayed to increase tonnage, quality will decline. Roots will be over-mature and become woody and pithy and the market will not accept them.

To harvest burdock, shoots are first removed by slashing or mulching the tops, leaving approximately 10 cm of stalk. Roots are then loosened with a vibrating ripper then pulled out by hand. It may be possible to pick up the roots with a modified carrot harvester once they have been loosened. After the roots are lifted from the soil, they must not be left exposed to the hot sun as this causes them to wilt and the skin quickly oxidises and becomes discoloured. Harvesting should be carried out early in the morning and the burdock taken to a shady area or packing shed as quickly as possible.

The fresh market in Japan demands long, straight roots without any forks or side shoots. Roots need to be at least 60 cm long (preferably 70 cm) and between 16_35 mm diameter (see Table 3- - not availble in this version - for grade sizes). Shorter or forked roots may be sent for processing at reduced price.

Roots are then washed and side shoots and root hairs are removed. After washing and trimming, roots are graded and packed into plastic-lined 10 kg cartons. Table 4 (- not availble in this version) also lists the fresh market grades that are used in Japan.

Quarantine requirements

A declaration must be provided to the Australian Quarantine Inspection Service (AQIS) that the burdock crop has been inspected by an authorised person and is free of burrowing nematode (Radopholus similis). The crop must have been grown on a farm that has been inspected by soil sampling during the growing season and found to be free from Radopholus similis. Radopholus similis does not occur in the Riverina of New South Wales, but is present along the north-east coast of Australia, especially in banana-producing areas. A further requirement is that all soil must be removed from the roots.

Future outlook

It is evident that in Japan burdock brings higher prices in the first half of the year, particularly April, May and June. However, data of import into Japan (Table 3- not available in this version) have shown that the imported prices in April and May with ¥140/kg and ¥160/kg respectively were not as good as the average wholesale prices at Tokyo markets with ¥382/kg and ¥407/kg (Table 2 - not available in this version) for April and May respectively.

It is understood that the low imported prices are due to low production costs in such supplier countries such as the Philippines. Low Japanese yen currency (A$ = ¥88 at June, 1997) would also be an important factor for the import price into Japan. The break-even price for New South Wales burdock is
A$1.34/kg (Table 4 - not availble in this version).

It should be noted that the production costs vary between seasons, growing locations, time of consignment and the business resources. Break-even costs do not include profit or return on capital invested.

Key contacts

Key references

Honda, F. 1987 `Gobo' (Burdock) in Mame, Konsai no jojuna tsukurikata (High-tech to produce bean and root vegetables) Ienohikar, Tokyo (In Japanese).

Larcom, Joy 1991 Oriental vegetables: the complete guide for garden and kitchen Kodanshu Int. Ltd., Tokyo.

Nguyen, V.Q. 1992 Growing Asian vegetables Agfact H8.1.37, NSW Agriculture.

Nishi, T. 1982 `Gobo' (Burdock) in Yasai engei hando buku (A handbook of vegetable crops). Yokendo, Tokyo (In Japanese).

*About the author