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Yamaguchi, M. 1990. Asian vegetables. p. 387-390. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR.

Asian Vegetables

Mas Yamaguchi


  1. INTRODUCTION
  2. ASIAN VEGETABLES
  3. REFERENCES
  4. Table 1

INTRODUCTION

Recent Asian immigrants have brought about dramatic changes in the kinds of vegetables consumed in the United States, especially in localities where these peoples are concentrated. Thirty-seven years ago, Porterfield (1951) described vegetables in New York City's Chinatown and 15 years ago Yamaguchi (1973) reported on the production of oriental vegetables in the United States. At present, these vegetables as well as new ones, especially those originating from Southeast Asia, are finding a home as new crops in the United States. In this paper, I will present some of the more interesting of these "new crops" and some which I think have potentials as new exotic vegetables in western culinary recipes. Nutritional values of some of the vegetables are presented in Table 1.

ASIAN VEGETABLES

Note on US import restrictions

Zizania latifolia Turcz. (Z. aquatica L.). [Common names: water bamboo, Manchurian wild rice; coba, kuw-sun, kwo-bai, jiao-bai (China, Taiwan); makomo dake (Japan)]. Water bamboo belongs to the Poaceae (-Gramineae), the same family as the common bamboo (Phyllostachys spp.) and is closely related to wild rice (Zizania aquatica L.) of North America. Grown since ancient times, this aquatic plant is cultivated in all parts of Asia from Manchuria in the north through eastern China to Indo-China on the south and east to Japan and Taiwan. A perennial water bamboo can be grown in stagnant ponds and in poorly drained soils. Plants grow from 1.2 to 2.4 m in height and the fully elongated leaves measure from 30 to 60 cm in length. Enlarged stems are harvested, the upper leaves cut off and only the stem with husk-like wrapper leaves sent to market. The edible portion is the succulent stem after the husks are removed.

There are three types of water bamboo in China:
Green stem-a small plant with fine leaves, early maturing.
White stem-large plant, mid to late season.
Pink or red stem-large plant, mid to late season.

Water bamboo is propagated by tillers. The most vigorous plants with short stout stems, large abundant leaves and no signs of floral initiation are selected for propagation. Tillers are planted in a nursery and allowed to grow for a year before transplanting to the field. Also, clumps of 4 to 5 tillers may be transplanted directly into the field. Tops are trimmed to about 40 cm height before planting.

Preparation of the field is sin-similar to that for paddy rice. Clay type soil, high in organic matter and pH range of 5.5 to 6.0 is preferred. Transplants are put into the mud about 6 cm deep at 30 to 40 cm spacing and in rows 90 to 100 cm apart. After planting the water is raised to a depth of 10 to 15 cm. Fifteen cm water depth is optimum, but in hot weather, the level is raised to 20 cm.

Field plantings in the sub-tropics are made in January through March and in the temperate regions, in March through April. If plantings are made late, the growing season is shortened so yields are reduced. High light intensity is desirable and mean temperatures of 25°C is optimal. At 20°C, the plant grows poorly and the harvested stems are not tender. The crop is fertilized with nitrogen four times during the season, twice with phosphorus and once early with potassium containing fertilizer.

Stem enlargement occurs after about 4 months growth. Harvest is made in about 150 days from planting with the green type and about 170 days with the white and pink types. Stem enlargement is due to the fungus, Ustilago esculenta P. Henn. Evidently, the fungus prevents floral initiation but allows the stem to elongate and enlarge. Harvest must be made before the fungus goes into the reproductive phase when the black smut (spores) is produced. With time there appears black longitudinal streaks in the swollen stem and eventually the entire stem turns black, very much like the corn ear smut. Because water bamboo is a perennial and asexually propagated, the fungal organism is apparently transferred from mother plant to the daughter tillers.

In Taiwan, the harvested swollen stems with leaves trimmed off are placed in large vats filled with water. This is done to keep the temperature down and keep the stalks moist in order to retard the formation of black streaks. Lack of nutrients in the plant or low water level in the field causes the fungus to go into the reproductive phase much earlier reducing quality and yield. In Beijing in Northern China, transplants are brought from the southern province near Guangzhou (Canton) every 2 or 3 years because production declines. Plants can survive the freezing temperatures of December and January in Beijing.

Water bamboo is a very popular vegetable in China. The swollen stem is sliced and eaten raw or cooked. Although water bamboo has a much softer texture than regular bamboo, the tissues remain crisp when stir-fried.

If water bamboo is brought into the United States, would the fungus which is necessary to cause the stem to swell, infect the wild rice and reduce production? Tests need to be made to determine whether infection can take place. I think that water bamboo would do well in the swampy regions of the Southern United States and in areas where paddy rice is produced.

Nelumbo nucifera Gaertn. (Nelumbium nelumbo Druce). [Common names: Lotus root (rhizome), East Indian lotus, Egyptian lotus; lian, lin ngau (China, Taiwan); hasu (Japan for the plant), renkon (Japan for the edible storage rhizome)]. A perennial aquatic plant of East Indian origin and belonging to the Nymphaceae, the lotus was brought to China and Egypt thousands of years ago. From China it was taken to other parts of Asia including Japan and northern Australia.

The plant, long known for its beautiful flowers, is mainly grown for the edible storage rhizomes (60 to 120 cm long and 6 to 9 cm in diameter). The storage rhizomes appear segmented because the diameter at the node is from 1/3 to 1/2 the diameter of the internode. The proximal segment (internode) is long and somewhat tapered, the diameter at the distal end being larger than the proximal end. Lengths of the segments decrease with increasing distance from the origin. The number of segments vary from 2 to 6.

Longitudinal circular passages are present in each segment. There is one central passage surrounded by 7 larger diameter and 2 medium diameter passages at about middistance from the center to the epidermis. Alternately to 7 large passages are small diameter passages near the outer perimeter of the rhizome. These passages probably function as ducts for gaseous exchange to the atmosphere.

Although seeds are very long lived, (there are reports of germination after 500 years in the soil) propagation is usually from recently harvested or stored rhizomes. Rhizomes are planted in paddies similar to that for rice. In Taiwan, rhizomes with at least 3 segments are planted 9 cm deep into the mud at an angle of about 20° to 30°C with the proximal end above water level. At planting time water level is kept at 6 cm depth. With growth the water level is gradually raised to about 30 cm and is maintained at this level. With the first two leaves that emerge, the blades float on the surface of the water. Petioles of subsequent leaves subtend above the surface and the blades unfurl in the air. The leaves are peltate and the blades are 30 to 90 cm in diameter on long slender tubular petioles.

The first growth is vegetative. The stem diameter is small and the internodes long so that the rhizomes do not appear segmented. From each vegetative node a leaf is produced, each petiole taller than the previous one. However, the last leaf that emerges before the onset of storage rhizome formation, is shorter than the previous one. The rhizomes grow in about 30 cm deep in the mud. Flower stalks emerge in July from the vegetative nodes.

The segmented storage rhizomes begin to form about the beginning of August. Large healthy leaves produce many segments; small or diseased leaves produce few segments. No leaves are produced from these. By late September the storage rhizomes are fully developed.

Storage rhizomes can be harvested after 120 days in warm climates and after 150 to 180 days or after the leaves die in cold weather in cool climates. At harvest, the water is drained and the fragile rhizomes are dug carefully. In some farms in Japan, high pressure water stream is used to wash away the mud and expose the storage rhizomes. Yields vary from 3.5 to 4.5 metric tons per ha. Higher yields can be obtained if flowers are removed.

Lotus rhizome retain their crisp texture even when cooked. Thread-like mucilaginous strands exude from cut or broken surfaces when the pieces are pulled apart. Starch obtained from the storage rhizome has properties similar to that from arrowroot. Immature leaves including the petioles are used as greens. Mature seeds and carpets are eaten, both are reported by the Chinese to have medicinal qualities.

Lotus has been grown in the Imperial Valley of California and I believe it can be successfully grown in the southeastern United States.

Note on US import restrictions

Ipomoea aquatic Forsk (I. reptans Poir.). [Common names: Water convulvulus, water spinach, swamp cabbage; ung tsoi, weng kai (China, Taiwan); kang kong (S.E. Asia); asagao na, yu sai (Japan)]. Water convulvulus belongs to the Convulvulaceae (morning glory family) and the same genus as the sweet potato (Ipomoea batatas L.) Probably of Chinese origin, cultivation dates back to at least 300 AD It is a very important green vegetable in Southeast Asia, because it is easy to grow, high yielding, and very nutritious.

The plant is herbaceous, an aquatic or semi-aquatic annual with hollow stems and ovate to elliptic shaped leaves. It has a creeping growth habit but may grow erect in water.

There are two main cultivars, the white flowered green stemmed type used in dry land (moist soil) culture and the pink colored purple centered flowers with white stems which are planted in flooded lands.

The green stem type is usually propagated by sowing seeds directly in the bed. Plants are spaced 12 cm apart and fertilized heavily with organic materials. When rainfall is not adequate, the crop is irrigated. Harvest of the entire plant can be made 50 to 60 days after planting.

Propagation is by stem cuttings for the white stem cultivar. Cuttings about 30 cm long with 7 to 8 nodes are obtained from the existing crop or from a nursery. The field is prepared as for paddy rice. Cuttings are planted 3 to 5 cm deep into the mud at about 40 cm spacing. Water is allowed to flow into the field as the crop grows, the depth is gradually increased to 15 to 20 cm. High rates of fertilizer are applied throughout growth; the water drained before application and flooded again a day afterwards. First harvest can be made a month after planting. Shoots are cut at about water level and bunched. After the first cutting, harvests can be made every 7 to 10 days. Annual yield of 90 metric tons per ha can be made from wet culture plantings.

Vigna sesquipedalis (L.) Fruw. (V. unguiculata (L.) Walp. sub spec. sesquipedalis (L) Verd.). [Common names: Yard long bean, asparagus bean; chang jiang dou, cheung kung tau (China, Taiwan); sitao (Philippines); zuyu roku sasage (Japan)]. Possibly of tropical African origin, the yard long bean (Fabaceae-Leguminosae), is a close relative of the cowpea. The crop is an annual trailing vine usually grown on poles or interplanted with corn for support of vines. Long slender immature pods which grow from 30 to 90 cm in length and about 0.9 to 1.0 cm in thickness are harvested.

There are two cultivars, a long white podded type which is harvested in the spring and the green podded type which is harvested from spring through fall in Southeast Asia. The crop is tolerant to high temperature and acid soils common in the tropics. It is intolerant to cold temperatures and under low soil moisture the pods are short and fibrous. Yard long beans can best be tried in regions where high temperatures prevent flower set of the common snap bean.

Cryptotaenia japonica Hassk. (C. canadensis D.C. var. japonica Makino). [Common names: Mitsuba, Japanese honeworts.] Probably of Japanese origin, n-mitsuba, meaning 3 leaflets is cultivated in Japan, Korea, and China. It is a member of the carrot family (Apiaceae-Umbelliferae). Like celery but a much smaller plant, it is grown for its long slender petioles and leaflets. The petioles are 10 to 15 cm long and 2 to 4 mm in thickness. When blanched or grown under crowded conditions, the petioles elongate to 30 cm or more in length.

In Japan, mitsuba is grown all year round in plastic houses, with the main production from fall through winter. Some growers culture the crop on polyfoam blocks which are floated on nutrient solution. Mitsuba is grown commercially near Los Angeles, California, in plastic houses for the oriental people in that area.

Mitsuba has a very distinct flavor; it is eaten raw in salads or as garnish and is used as flavoring in soups or cooked as greens.

Raphanus sativas L., cultivar 'Sing li mei'. [Common name: red fleshed radish]. In 1979, while visiting an agricultural experiment station in Japan, I saw some red flesh winter radish grown from seed brought from mainland China. While in China this summer, I saw this radish again. It was developed by a breeder at the Beijing Vegetable Research Center. The cultivar is named 'Sing li mei', meaning "the heart is beautiful" in Chinese. The roots I saw were grown the previous fall and put into storage and kept until mid June. The pigment is probably an anthocyanin.

The radishes are eaten raw as a snack food; they are crisp and sweeten somewhat during storage. This radish cultivar should prove popular in the western world in adding color to salads and for vegetable hors d'oeuvres.

REFERENCES


Table 1. Nutritive composition per 100 g edible portion of some Asian vegetables.

Constituent Water bambooz (Zizania latifolia) Water convulvulusy (Ipomoea aquatica) Lotus rhizomey (Nelumbo nucifera) Yardlong beansy (Vigna sesqui pedalis) Radishy (Raphanus sativus)
Water (%) 92.6 92 75 89 94
Energy (Cal) 26 25 69 30 13
Protein (g) 1.2 2.6 2.6 2.8 0.6
Fat (g) 0.2 0.2 0.1 0.4 0.1
Carbohydrate (g) 5.5 3.4 14.7 3.8 2.7
Fiber (g) 1.0 - - - -
Ash (g) 0.5 - - - -
Minerals
Ca (mg) 5 95 45 50 27
P (mg) 36 40 100 59 24
Fe (mg) 0.6 2.2 1.6 1.0 0.4
Na (mg) - 6 40 4 30
K (mg) - 370 730 210 190
Mg (mg) - 49 25 51 22
Vitamins
A (I.U.) 0 3500 0 1400 0
Bl (mg) 0.09 0.03 0.16 0.13 0.02
B2 (mg) 0.04 0.10 0.22 0.11 0.02
Niacin (mg) 0.2 0.9 0.4 1.0 0.2
C (mg) 2 55 44 32 22
zLeung, W.W. et al. (1952).
yHoward, F.D. et al. (1962).


The fungus Ustilago esculenta, which causes stem enlargement of Manchurian wild rice, Zizania latifolia is a regulated organism. Bringing infected Z. latifolia into the United States is a violation of the Federal Plant Pest Act regulations. The fungus poses a threat to native species of wild rice. One illegal planting of Manchurian wild rice was eradicated in California in 1991. Infected wild rice has been detected in Louisiana and authorities are developing recommendations to address the issue.

Ipomoea aquatica is a federal noxious weed. Under authority of the Federal Noxious Weed Act, the Animal and Plant Health Inspection Service prohibits the importation and interstate movement of this species, except under USDA-issued noxious weed permit. Although I. aquatica is prized as a vegetable, it is also an agricultural and environmental pest, reducing yields of rice and sugarcane in other parts of the world, and affecting aquatic ecosystems, irrigation systems, reservoirs, and navigation and recreation on fresh waterways.

APHIS (Animal and Plant Health Inspection Service) encourages importers to be aware of import restrictions meant to protect American agriculture and natural areas. Please refer to the APHIS web site for more information: http://www.aphis.usda.gov/ppq/permits/