Ipomoea aquatica (swamp morning-glory)

Weed Damage

Ipomoea aquatica grows very rapidly and becomes a weed in some habitats (Parham, 1958; Varshney and Rzoska, 1976). The long floating stems form a dense network across bodies of fresh water. This network supports leaves and flowers, which rise above the water surface and may impede water flow and navigation (Ashton, 1973). I. aquatica is also a major broadleaved aquatic weed of dry-seeded wetland rice (Raju and Reddy, 1986; Jena and Patro, 1990).

In Florida (USA), where the flat landscape permits sheet flow of water during periods of heavy rain, I. aquatica is considered a serious threat to flood control. Since the late 1970s, the Florida Department of Natural Resources has eradicated over 20 small infestations of I. aquatica that escaped from illegal plantings. It is considered a significant threat to Florida's waterways and wetlands (Westbrooks, 1989).

In natural settings, such as rivers and lakes, I. aquatica may outcompete native vegetation and limit the use of these waters. (Such settings may pose problems for regular monitoring and environmental constraints may exist, so that I. aquatica is difficult to detect and control.) In a Florida study, I. aquatica left unattended in a tank with several other species protruded up through a dense mat of Hydrilla verticillata and then grew over the remaining species (Gilbert, 1984).

Canals used for irrigation in the Sudan are conducive to the spread of aquatic weeds. Among the most prevalent species are Cyperus rotundus, I. aquatica and Panicum repens on canal banks, and Chara globularis, Najas pectinata, Ottelia alismoides and Potamogeton spp. anchored in the canal mud. Although mechanical clearance using rakes and chains is often uneconomic, the possible contamination of irrigation water discourages chemical control (Beshir, 1978).

Positive Attributes

Culinary uses
A plant that is presumed to be I. aquatica was being used as a food plant during the Chin Dynasty in China as early as 290 AD (Edie and Ho, 1969). Today, it is grown as a vegetable crop in many tropical countries and was suggested as a potential vegetable crop for south Florida by Ochse (1951). The highly nutritious stems and leaves are eaten raw, boiled, stir fried, steamed, or pickled throughout Asia. The foliage is high in protein, vitamin A, iron, calcium, and phosphorus (Bautista et al., 1988). It is also eaten as a vegetable by Asian-Americans in a number of states in the USA (Westbrooks, 1989). The composition of the essential oil of fresh leaves and stems has been investigated to identify the flavour components (Kameoka et al., 1992).

Yield as a crop
Annual production of I. aquatica ('water spinach') in Hong Kong has been estimated at 3-5 million kg (Edie and Ho, 1969). When grown as a crop, yields of up to 100,000 kg/ha have been reported in Hong Kong (Edie and Ho, 1969). Similar yields were reported in field trials in south Florida (Snyder et al., 1981). Under optimum conditions, it can grow up to 16 cm per day (Gilbert, 1984). Under upland cultivation, yields range from 7 to 30 tonnes/ha of fresh produce per crop. Under wet cultivation, annual yields are estimated to be from 24 to 100 tonnes/ha. Annual production of floating water spinach in Thailand is reported to be 90 tonnes/ha. In Malaysia, water spinach is cultivated commercially on 600-1,100 ha with a total production of 60,000-220,000 tonnes/year. In 1992, in Thailand, Malaysia and Singapore, farmers' revenues from production of water spinach were US$ 0.05-0.40 per kg (Westphal, 1992).

Medicinal uses
According to various sources, I. aquatica has been used extensively as a medicinal plant: as a mild laxative in India (Subramanyam, 1962); in the treatment of ringworm (Anonymous, 1959); and as a poultice in febrile delirium (Anonymous, 1959).

Use as an Animal Feed
Plants may be fed to livestock, pigs, ducks, and chickens (Brown, 1946; Westphal, 1992).

Ability to remove heavy metals
Field studies in the Makkasan Reservoir, Thailand revealed that maximum biomass per clump of I. aquatica was reached 8 weeks after sowing. The average absorption of N, P, K, Ca and Mg was 3.59, 0.54, 4.40, 0.86 and 0.20 (% dry weight). The average heavy metal absorption of Fe, Mn, Zn, Pb, Cu and Cd was 908.35, 202.36. 86.38, 31.48, 11.39 and 0.74 (µg/g dry weight) (Stripen et al., 1991). This plant may be useful in removing nitrates from contaminated water, such as farm drainage and municipal waste (Snyder et al., 1981).