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Description: Ipomoea aquatica, known by several names in English, such as Swamp morning-glory or Water spinach, is a creeping or floating, normally subaquatic, herbaceous vine that is only found in fresh water and can be both a useful crop and an invasive species. Its alternately arranged leaves vary in shape but are commonly oblong-lanceolate; normally the leaves are about 5-15 cm (2-6 in) long and 2-10 cm (1-4 in) wide with petioles 3-10 cm (1-4 in) long. Its flowers are produced in several cymes with typical morning-glory shape; and the fused corolla is usually 4-5 cm (~2 in) long, pinkish-violet in color but darker in the throat (and rarely it is whitish). Its small seeds (four or less per spherical or ovoid fruit capsule) are about 1 cm (~0.4 in) long and normally, but not always, have fine grayish hairs on the surface. (e.g., see Holm et al. 1997:414; Stone 1970).
Distribution: Ipomoea aquatica is adapted to fresh water aquatic habitats, invading canals and ditches, but also naturalizes in lakes and marshes; in addition, it also grows profusely in moist soil and still or moving waters. Due to its abundant growth, this species can invade moist cultivated areas such as rice fields, sugar cane plantations and other places with variable water levels. It originated in tropical Asia (possibly India) and can be found in South and South-East Asia, tropical Africa, South and Central America and Oceania; however, it is only in South and South-East Asia that it is a significant leafy vegetable. It is intensively grown and frequently eaten throughout South-East Asia, Hong Kong, Taiwan and southern China. “Above all else, it is a … creeper on the banks of muddy streams and ponds, awaiting the opportunity to reach out over the water surfaces to form mats with other vegetation” (Holm et al. 1997:412, 414).
General Uses: I. aquatica is a very worthwhile vegetable crop in tropical countries where, in some cases, it has been cultivated for centuries. Nevertheless, it has the potential to damage natural wetland ecosystems as well as subsistence or commercial rice and sugarcane production, critical irrigation systems, and even human navigation and recreation areas have stimulated its listing as a Federal Noxious Weed in the United States. Although it has possible monetary or social benefits from deregulation of this potential vegetable crop, these are offset by the likely damage it can produce and the cost of controlling its unwanted spread. On the other hand, where it has been under control, its food value is much appreciated; for example, its young stem and leaves are cooked or lightly fried in oil and can be eaten in wide variety of dishes. The vines are also used as fodder for livestock in some places, and in parts of Malaysia it is grown extensively in fish ponds and fed to domesticated pigs. The very nutritious stems and leaves which are high in protein, vitamin A, iron, calcium and phosphorus can be eaten raw, boiled, stir fried, steamed, or pickled as they are throughout much of tropical Asia. I. aquatica has been used extensively as a medicinal plant, for example, as a laxative and in treatment of ringworm. Clearly this Swamp morning-glory species has both positive and negative aspects in terms of food and medicine versus serious environmental impact.
Uses by Island or Island Group: In Microneisa,according to Fosberg and Sachet (1977:8), I. aquatica is “planted or spontaneous in marshy places or in open water,” and has been found on Pagan, Saipan, Tinian, Rota, Guam in the Mariana Islands, as well as on the islands of Palau, Yap, Ulithi, Chuuk, Satawan in the Caroline Islands, and on Tarawa in Kiribati. Additional islands in Micronesia where I. aquatic is also known to occur are noted in the discussion below.
Uses in Palau: The leaves and stems of the alien “Swamp morning-glory” or “Water spinach,” (I. aquatica) known locally in Palau as Kangkum (Otobed 1971)are eaten as vegetables or pot herb in these islands (e.g., see Fosberg and Sachet 1977:8); I. aquatica is also used for pig fodder in Palau. Today I. aquatica can be found growing in abundance in some taro patches or ponds Palau.
Uses in Yap: Around residential areas on Yap, plantings of newly introduced vegetable crops such as I. aquatic,known locally as Kaangkoong or Kaangkuung, have been undertaken (e.g., Hunter-Anderson 1991:36 also see Shovic 1997).
Uses on Ulithi Atoll: The alien Kaangkoong (I. aquatica) aquatic herb is now commonly found growing in profusion throughout many farms on Ulithi Atoll, but it is rarely utilized for food or other purposes on this atoll (Onjo et al. 2003); however, parts of this species are reported to have been consumed “fried with meat” on Ulithi (see Fosberg and Sachet 1977:8).
Uses in Mariana Islands: According to Fosberg and Sachet (1977:8, citing Whiting 1965),
“Leaves [of this species are] cooked as greens especially to serve with fish” on Guam.
Uses on Puluwat Atoll: Swamp morning-glory or Water spinach(I. aquatica) is a relatively new crop on Puluwat is now which cultivated on the oval taro mounds of Colocasia and Cyrtosperma; These mounds “stand about 0.5 m above the water table and measure about 50 m2 in area, are made by anchoring coconut and pandanus trunks to form an oval base which is then filled with organic materials” (Manner 1993:34, also see Manner 1989).
Uses in Chuuk: Introduced by Japanese into Chuuk as a food plant, the young tips of alien I. aquatica, are said to be an excellent vegetable very much like our spinach (see Fosberg and Sachet, 1977:8, citing voucher specimens of Pelzer 1946 and Fosberg 24417, also see Manner 2013:231).
Uses in Pohnpei: The alien I. aquatica, also known as Kangkong on Pohnpei, is used as a food, source with the tuber being “cooked in soup,” and similar to some other areas of Micronesia, the whole plant is fed to pigs (Balick et al. 2009:359).
Uses in Kiribati: Known as Te kangkong or Te ruku on Nauru Island, Ipomoea aquatica is a recently introduced food crop.
Uses in Nauru: I. aquatica is said to have been introduced to this island before World War II. It is reportedly known locally on Nauru as “lorenzo”by the Nauruan people (this name is probably from the Japanese who introduced it or cultivated it and referred to it as “horenzo”); I. aquatica is also known in Nauru as “ung ts'oi” by the local Chinese and “cangcong” by the local Filipino workers (Thaman 1994:34). I. aquatica is a food plant on Nauru “in Chinese and Filipino gardens at Location and Topside Workshop gardens; naturalized in muddy areas of Buada Lagoon, where it was formerly planted by the Japanese during World War II….[and the plant’s tender] leaves and shoots [are] cooked as a green vegetable,” with its propagation normally involving cuttings (Thaman 1994:116-117).