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28 August 2023

Ipomoea aquatica (swamp morning-glory)

Datasheet Types: Invasive species, Pest, Host plant, Crop

Abstract

This datasheet on Ipomoea aquatica covers Identity, Overview, Associated Diseases, Pests or Pathogens, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Prevention/Control, Management, Genetics and Breeding, Food Quality, Economics, Further Information.

Identity

Preferred Scientific Name
Ipomoea aquatica Forssk.
Preferred Common Name
swamp morning-glory
Other Scientific Names
Ipomoea natans Dinter & Suess
Ipomoea repens Roth
Ipomoea reptans Poir.
Ipomoea sagittifolia Hochr.
Ipomoea subdentata Miq.
International Common Names
English
Chinese spinach
Chinese water spinach
Chinese watercress
river spinach
swamp cabbage
water convolvulus
water morning glory
water spinach
Spanish
batata acuática
batata aquática
French
liseron d'eau
patate aquatique
Chinese
kong xin cai
ong choy
tong cai
ung tsoi
weng cai
Local Common Names
Bangladesh
kolmi shak
Cambodia
trâkuön
Denmark
vandspinat
Fiji
ndrinikava
Germany
Sumpftrichterwinde
Sumpf-Trichterwinde
Sumpf-Wasserspinat
India
ganthain
kalami sag
kalmisak
karmi
koilangu
nadishaka
nalanibhaji
nali
nari
patuasag
sarnali
sornalika-sag
tooti koora
tutikura
vellai kerai
vellaikeerai
Indonesia
kangkong
kangkung,
Italy
convolvolo d'acqua
patate acquatica
vilucchio d'acqua
Japan
asagaona
en-sai
kankon
ku-shin-sai
tsuu sai
you sai
Laos
phak bong
Malaysia
kangkong,
kangkung
kankong
kankung
Papua New Guinea
kangkong
kango
Peru
camotillo
Philippines
balanñgog
cancong
galatgat
kangkong
tangkong
tangkung
Portugal
batata acuática
batata aquática
Sudan
argali
Sweden
vattenspenat
Thailand
bai phai
gka-lampok
paakboong
pak boong chin
phak bung
USA
creeping swamp morning-glory
water convolvulus
water green
Vietnam
giau muong
rau muống
ung thái

Pictures

Flowering habit of Ipomoea aquatica (swamp morning-glory). Ukumehame, Maui, Hawaii, USA. October 2012.
Flowering habit
Ipomoea aquatica (swamp morning-glory); Flowering habit. Ukumehame, Maui, Hawaii, USA. October 2012.
©Forest & Kim Starr - CC BY 4.0
Flowers of Ipomoea aquatica (swamp morning-glory). Ukumehame, Maui, Hawaii, USA. October 2012.
Flowers
Ipomoea aquatica (swamp morning-glory); Flowers. Ukumehame, Maui, Hawaii, USA. October 2012.
©Forest & Kim Starr - CC BY 4.0
Habit of Ipomoea aquatica (swamp morning-glory). Ukumehame, Maui, Hawaii, USA. October 2012.
Habit
Ipomoea aquatica (swamp morning-glory); Habit. Ukumehame, Maui, Hawaii, USA. October 2012.
©Forest and Kim Starr/via Starr Environmental - CC BY 4.0
Foliage of Ipomoea aquatica (swamp morning-glory). Keehi Lagoon, Oahu, Hawaii, USA. May 2008.
Leaves
Ipomoea aquatica (swamp morning-glory); Foliage. Keehi Lagoon, Oahu, Hawaii, USA. May 2008.
©Forest & Kim Starr - CC BY 4.0
Foliage of Ipomoea aquatica (swamp morning-glory) in a garden setting. Sand Island, Midway Atoll, Hawaii, USA. May 2008.
Foliage
Ipomoea aquatica (swamp morning-glory); Foliage in a garden. Sand Island, Midway Atoll, Hawaii, USA. May 2008.
©Forest & Kim Starr - CC BY 4.0
Foliage of Ipomoea aquatica (swamp morning-glory) in a garden setting. Sand Island, Midway Atoll, Hawaii, USA. May 2008.
Foliage
Ipomoea aquatica (swamp morning-glory); Foliage in a garden. Sand Island, Midway Atoll, Hawaii, USA. May 2008.
©Forest & Kim Starr - CC BY 4.0
Young seedlings of Ipomoea aquatica (swamp morning-glory) in hydroponics greenhouse. Hydroponics Greenhouse, Sand Island, Midway Atoll, Hawaii, USA. June 2017.
Hydroponics culture
Ipomoea aquatica (swamp morning-glory); Young starts. Hydroponics Greenhouse, Sand Island, Midway Atoll, Hawaii, USA. June 2017.
©Forest & Kim Starr - CC BY 4.0
Greenhouse grown leaves of Ipomoea aquatica (swamp morning-glory). Hydroponics Greenhouse, Sand Island, Midway Atoll, Hawaii, USA. June 2017.
Hydroponics culture
Ipomoea aquatica (swamp morning-glory); Greenhouse grown leaves. Hydroponics Greenhouse, Sand Island, Midway Atoll, Hawaii, USA. June 2017.
©Forest & Kim Starr - CC BY 4.0
One of the culinary uses of Ipomoea aquatica (swamp morning-glory). Clipper House, Sand Island, Midway Atoll, Hawaii, USA. June 2008.
Culinary use
Ipomoea aquatica (swamp morning-glory); Culinary use. Clipper House, Sand Island, Midway Atoll, Hawaii, USA. June 2008.
©Forest & Kim Starr - CC BY 4.0
Cultivation of Ipomoea aquatica (swamp morning-glory) in residential areas.
Cultivation
Ipomoea aquatica (swamp morning-glory); Cultivation.
©A.R. Pittaway

Overview

Ipomoea aquatica, also called ‘water spinach’ or kangdong, is a perennial or occasionally annual, trailing, creeping, floating or erect herb. It is primarily a plant of the humid tropical lowlands, requires short-day conditions and a warm, wet climate to flourish. Mean temperature has to be above approximately 25°C and the species thrives best in water or relatively moist clay-loam or loam soil. It is propagated from seed or stem cuttings and is cultivated and eaten as a leafy vegetable in South-east Asia, Taiwan and southern China, and is probably native to India and South-east Asia. Harvesting can start 30-40 days after sowing. As upland cultivation has a short growing period of one crop, pests and diseases do not cause much harm. The young tops or plants (stem and leaves) are cooked like spinach or lightly fried in oil and eaten as a vegetable in various dishes. Production figures are difficult to obtain due to the lack of any registration of information on production and trade. The species naturalizes easily and can now be found wild in South and South-east Asia, tropical Africa, and South and Central America. In many areas it is considered to be a troublesome weed and it can cause environmental damage as it is a fast-growing and aggressive plant, which can be a serious threat to waterways.

Summary of Invasiveness

Ipomoea aquatica is an aquatic, semi-aquatic or terrestrial herbaceous vine; it is a perennial or sometimes annual species growing only in freshwater habitats. It is a popular cultivated vegetable in South East Asia and southern China. It has been introduced intentionally in the tropics as a cultivated plant. I. aquatica can invade moist cultivated areas and can become an invasive problem in some tropical regions outside its native range. It forms dense floating mats of intertwined stems on water surfaces, shading out and competing with native submersed and emergent species. It is a common serious weed of rice and other crops in 60 countries in many areas in Asian tropical countries and in natural wetlands, lakes and river shorelines. Considered an invasive species on Pacific and Indian Ocean islands, in Cuba and the USA (California and Florida), I. aquatica is the second greatest problem plant species in the Philippines where it tends to overgrow freshwater marginal areas. It is listed as a Federal Noxious Weed in the USA.

Taxonomic Tree

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Notes on Taxonomy and Nomenclature

The family Convolvulaceae has a neotropical distribution and includes 50-60 genera and about 1600-1700 species (Mabberley, 1987). This family contains many weedy species in temperate regions, and in the tropics many species are valued as ornamentals, and as medicinal and food crops. (Simpson and Ogorzaly, 1995). Ipomoea is the largest genus within the Convolvulaceae with about 500-650 species (Wilkin, 1999; Mabberley, 2008). Ipomoea aquatica is a semi-aquatic, tropical plant grown as a vegetable for its tender shoots and widely cultivated in South East Asia, East Asia and South Asia. Ipomoea reptansPoiret (1814) is a commonly used incorrect synonym (Westphal, 1992).
In their monograph of the 425 species of Ipomoea in the New World, Wood et al. (2020) provide notes on salient characteristics and taxonomic issues related to individual species including I. aquatica.

Plant Type

Annual
Perennial
Seed / spore propagated
Vegetatively propagated
Aquatic
Broadleaved
Herbaceous
Vine / climber

Description

The following description is from Reed (1977), Westbrooks (1989) and Scher et al. (2015):
Ipomoea aquatica is a sprawling vine, annual or perennial, creeping on mud or floating on water; stems terete, branched, hollow and succulent when floating, otherwise solid and firm, up to 3 m long, to 1 cm in diameter. Leaves emersed, glabrous, alternate; petioles succulent when grown in water, 3-20 cm long; blades greenish-brown, triangular, ovate, lanceolate, or linear, entire to dentate, 3-15 cm long, 1-12 cm across, bases truncate, cordate, hastate, or sagittate, lobes rounded to acute, entire to dentate. Inflorescences axillary cymes, with one to a few flowers; peduncles 0.5-18 cm long. Flowers perfect, hypogenous, large and showy; pedicels 1-6.5 cm long, with minute bracts at base; sepals glabrous, unawned, ovate, the inner slightly longer than outer, 7-10 mm long; corolla funnel shaped, glabrous, pink, often with darker eye, sometimes white or cream, 2.5-5.5 cm long, 2-4 cm wide; stamens included, shorter than corolla, adnate with petals above the base, filaments hairy at the base, anthers dehiscing longitudinally; carpels glabrous, locules mostly 2, style included, shorter than corolla, ovules mostly 4. Fruit a capsule, glabrous, globose to ovoid, 8-10 mm long; seeds 4 or fewer, brown or black, mostly pubescent, 3-ranked, rounded on back, 4.5-5.5 mm long, 3.5-4.5 mm wide, 2.5-3.5 mm thick. The seeds have an omega-shaped border that surrounds the hilum.

Distribution

Ipomoea aquatica is native to southern Asia (Li, 1970; Van and Madeira, 1998). More recently, Langeland and Burks (1998) indicate China as its native range, but Van (1998) suggests India and China. The origin of this species is currently debatable, and there is doubt as to whether this species is native in Africa and North Australia (Austin, 2007). It is widely cultivated and it occurs in nearly all countries of tropical regions in South, South East and East Asia, including Japan and Korea. In Africa, it occurs from Mauritania and Senegal, east to Eritrea and Somalia, and south to South Africa; it is also found on some Indian Ocean islands (PROTA, 2018; WCSP, 2018). It is distributed throughout Australia except in the south west (Atlas of Living Australia, 2018), and in the Pacific Islands, tropical South America, Central America, the Caribbean (Cuba and Puerto Rico) and the USA, where it has been introduced in Hawaii, Florida and California (USDA-NRCS, 2018).
Wood et al. (2020) in their monograph of the 425 Ipomoea species of the New World provide information on the distribution of I. aquatica.

Distribution Map

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Distribution Table

This content is currently unavailable.

History of Introduction and Spread

Ipomoea aquatica was introduced in tropical Asian countries from China through trade around the second century BC and introduced in Africa from China in the 14th century (Austin, 2007). The first record of it on a Pacific island was in Samoa in 1956 (Parham,1972); it was introduced in continental USA in the mid-1970s (Langeland et al. 2008; Chilton, 2017). It is a popular cultivated vegetable in South East Asia and southern China; it is widely cultivated and naturalized in Africa, Asia, Australia, the Pacific Islands and South America. In the USA, this species is cultivated in California, Texas and the US Virgin Islands (Van and Madeira, 1998; Harwood and Sytsma, 2003). Its wide use as a vegetable crop in Asia and among some communities in Florida, Hawaii, Texas and California may cause further spread in these areas (Harwood and Sytsma, 2003) but it is currently limited to only a few counties in Florida and California, and all but two islands in Hawaii.

Risk of Introduction

Ipomoea aquatica is expanding globally into other parts of Asia, Africa, Australia, several Pacific Islands and South America (Langeland and Burks, 1998). Introduced as a cultivated plant, which then escaped (Lee, 1998), its unintentional introduction as a seed contaminant (USDA-ARS, 2018) is highly likely. Originating from Asia, the potential for dispersal is high, but the plant is limited to subtropical areas only.
Ipomoea aquatica is regulated as a US Federal Noxious Weed and as a state noxious weed in over ten states (Chilton, 2017; USDA-NRCS, 2019). According to a risk assessment undertaken in Oregon (Harwood and Sytsma, 2003) and in Texas (USA) (Chilton, 2017), I. aquatica appears to be a relatively low-risk species. After 20 to 30 years of commercial production, this species has established outside cultivation areas in only small stands in California and Florida (Chilton, 2017). Although the sale and distribution of I. aquatica is prohibited in Florida due to a state and federal listing as a prohibited plant and noxious weed, it is still repeatedly introduced there (R Kipker, Florida Department of Environmental Protection, unpublished data). There is no evidence that this species can grow outside tropical climates (Harwood and Sytsma, 2003); therefore, its spread in the USA is likely to be limited (Samkol, 2005; Chilton, 2017).

Means of Movement and Dispersal

Natural Dispersal

Seeds and plant fragments can be carried downstream by water currents (Langeland et al., 2008) that allow easy translocation to new areas. Canals used for irrigation in the Sudan are conducive to the spread of aquatic weeds (Westbrooks, 1989).

Vector Transmission (Biotic)

Ipomoea aquatica may spread by seed, plant fragments or whole plants by animals and humans (Patnaik, 1976). It is easily propagated from cuttings (Steenis, 1953).

Accidental Introduction

The unintentional introduction of I. aquatica as a seed contaminant is highly likely (USDA-ARS, 2018). The seeds have been intercepted as contaminants of Ipomoea cairica seeds, Citrus sp. seeds, rice seeds, Sesamum indicum seeds, Cucumis sp., Pittosporum sp. leaves, Cuminum sp. seeds and tractor trailer debris (Interceptions Records, USDA, Animal and Plant Health Inspection Service, Riverdale, Maryland, USA).

Intentional Introduction

Ipomoea aquatica has been introduced as a cultivated plant, which then escaped (Lee, 1998). Since the late 1970s, the Florida Department of Natural Resources has eradicated over 20 small infestations of I. aquatica that escaped from illegal plantings (Westbrooks, 1989).

Pathway Causes

Pathway causeNotesLong distanceLocalReferences
Crop production (pathway cause)Cultivated for human consumption-escape from cultivationYesYes

Pathway Vectors

Pathway vectorNotesLong distanceLocalReferences
Plants or parts of plants (pathway vector)Contaminant of crop seedsYesYes
Water (pathway vector)  Yes

Hosts/Species Affected

Ipomoea aquatica is a major broadleaved aquatic weed of dry-seeded wetland rice (Haselwood and Motter, 1966; Raju and Reddy, 1986; Jena and Patro, 1990; Holm et al., 1997). It is a weed in rice crops (Holm et al., 1997), and in other moist cultivated areas, such as sugarcane fields, and many other crops in Asian countries (PIER, 2018).

Host Plants and Other Plants Affected

HostFamilyHost statusReferences
Oryza sativa (rice)PoaceaeMain 

Similarities to Other Species/Conditions

Ipomoea aquatica is similar to the sweet potato (Ipomoea batatas), especially when growing terrestrially, but the two plants can be easily distinguished because I. aquatica has hollow stems and an aquatic habitat (Langeland et al., 2008). The leaves of I. batatas are broader, ovate to palmately lobed, whereas those of I. aquatica are relatively narrow, elongate, sagitate to basally cordate (Acevedo-Rodríguez, 2005).

Habitat

Ipomoea aquatica is found in freshwater aquatic habitats (PIER, 2018), and classified as an obligate hydrophyte plant in the USA (USDA-NRCS, 2018). It is a marginal, creeping, perennial aquatic plant that grows well in moist soil or in still to flowing waters (Langeland and Burks, 1998). It may spread over the surface of a pond, muddy stream banks and lakes, or over an irrigation or drainage ditch. It can be found in flooded lowland fields and marshes, in dense masses in rice paddies (Holm et al., 1997), and in lakes and waste areas (Flora of China Editorial Committee, 2018).

Habitat List

CategorySub categoryHabitatPresenceStatus
Terrestrial Managed forests, plantations and orchardsPresent, no further detailsHarmful (pest or invasive)
Terrestrial Protected agriculture (e.g. glasshouse production)Present, no further detailsHarmful (pest or invasive)
Terrestrial WetlandsPresent, no further detailsHarmful (pest or invasive)
TerrestrialTerrestrial ‑ Natural / Semi-naturalRiverbanksPresent, no further detailsHarmful (pest or invasive)
Freshwater LakesPresent, no further detailsHarmful (pest or invasive)
Freshwater Rivers / streamsPresent, no further detailsHarmful (pest or invasive)
Freshwater PondsPresent, no further detailsHarmful (pest or invasive)

Biology and Ecology

Genetics

The chromosome number reported for I. aquatica is 2n = 30 (Westphal, 1992). Some partial DNA sequences have been determined for this species, as listed in the Genbank database (see list in Atlas of Living Australia, 2018). For further information on chromosome counts, see Missouri Botanical Garden (2018).
A number of cultivars is reported for I. aquatica (Snyder et al., 1981). Two main wild biotypes are reported throughout South East Asia (Cornelis et al., 1985; Westphal, 1992). The first, known as ‘Red’, has green/purple stems, dark green leaves with
sometimes purple petioles and veins, and light purple to white flowers; the second, known as ‘White’, has green/white stems, green leaves with green/white petioles and white flowers.

Reproductive Biology

Vegetative multiplication is very important in the propagation of I. aquatica, by the stems rooting at nodes and also by stolons (Edie and Ho, 1969; Schardt and Schmitz, 1990).
Roots are produced at stem nodes that come in contact with water or moist soil. New plants can root within a week (Satpathy, 1964). Once roots are established, the plant grows as a trailing vine. Stems that have grown out over water have round, hollow stems and petiolate, basally lobed leaves.
Reproduction is also by seed, mostly during the dry season, when it grows on temporary flooded land. Fresh, mature seeds display primary dormancy within 15 days after harvest. Natural germination occurs following an after-ripening period and scarification of the seed coat. Dormancy can be broken by various methods of scarification, such as naturally occurring abrasion by soil particles, prolonged microbial attack or ingestion by animals (Datta and Biswas, 1970). Germination rates of I. aquatica seeds are usually less than 60%, with black-seeded types showing higher germination rates than light-coloured seeds. Two to three weeks after sowing, the plants start developing strong lateral branches. After this, the main axis and both lateral branches produce about one leaf every 2-3 days. Flowering starts 48-63 days after sowing (Westphal, 1992).

Physiology and Phenology

Although flowering and fruiting in India occur during the rainy season, generally flowering is observed throughout the year (Flora of Pakistan, 2018; India Biodiversity Portal, 2018). Under good conditions, I. aquatica can produce 190,000 kg fresh weight biomass per ha in 9 months. It flowers in the warm months and produces 175-245 seeds per plant during the peak season (Langeland and Burks, 1998).
Ipomoea aquatica can behave as an aquatic, semi-aquatic or as a terrestrial plant with reduced leaves and stems in dry months. When soil moisture is lacking, it may appear to be in hibernation (Holm et al., 1997). Under dry land conditions, I. aquatica will grow as an erect herb (Edie and Ho, 1969). It can then become an annual plant, when the dry conditions do not allow its survival.
Annual production of I. aquatica 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 I. aquatica in Thailand is reported to be 90 tonnes/ha. In Malaysia, the species is cultivated commercially on 600-1100 ha with a total production of 60,000-220,000 tonnes/year.
The submerged components of I. aquatica show some resistance to adverse conditions, ensuring perpetuation of the species when favourable conditions return. Nitrogen and phosphorus are important growth factors in this species. I. aquatica shows a high absorption capacity for ammonium-nitrogen. Potassium and calcium were relatively high, whereas magnesium and sodium were low in the habitats studied (Chin and Fong, 1978).

Longevity

Ipomoea aquatica grows as a perennial in humid sub-tropical and tropical climates and as an annual in drier, much cooler climates. Plants are damaged at temperatures below 10°C (Iplantz, 2023).

Environmental Requirements

Ipomoea aquatica is adapted to a warm, moist climate and is confined to the tropics and to subtropical zones; it cannot survive frost (Flora of China Editorial Committee, 2018). It grows poorly when temperatures are below 23.9°C (Harwood and Sytsma, 2003).
Ipomoea aquatica is thought to be a quantitative short-day plant. It produces optimum yields in the lowland humid tropics that have stable high temperatures and short-day conditions. Optimum growth occurs in full sunlight. Marshy lands and waterlogged soils are ideal for its growth. Shallow ponds, ditches, peripheries of deep ponds, tanks and slopes of wet soils are also suitable. It is adapted to a wide range of soil conditions, with clay soils (heavy or silty) being generally suitable. Soils with a high percentage of organic matter are preferred. The optimum pH range for growth is 5.3-8.5 (Tiwari and Chandra, 1985; Westphal, 1992).
Low temperature, shade and salinity are limiting factors for growth of I. aquatica. It grows poorly in cold weather but can tolerate light frost that affects only the outer leaves (Snyder et al., 1981). The seeds can withstand some freezing (Gilbert, 1984). Huang (1981) observed that it does not grow at day/night temperatures below 20°/15°C. It has low shade tolerance: plants grown in the shade are weak and thin (Tiwara and Chandra, 1985). I. aquatica is not tolerant of brackish or salt water (Backer and Brink, 1965).

Climate

Climate typeDescriptionPreferred or toleratedRemarks
A - Tropical/Megathermal climateAverage temp. of coolest month > 18°C, > 1500mm precipitation annuallyPreferred 

Latitude/Altitude Ranges

Latitude North (°N)Latitude South (°S)Altitude lower (m)Altitude upper (m)
3523  

Air Temperature

ParameterLower limit (°C)Upper limit (°C)
Absolute minimum temperature20 
Mean minimum temperature of coldest month24 

Soil Tolerances

Soil texture > Heavy
Soil drainage > Seasonally waterlogged

Notes on Pests

Owing to the short growing period of one crop of upland kangkong, diseases and pests do not cause much harm. Where ratooning is practised they can become a nuisance. White rust (Albugo candida) is reported from Thailand, Indonesia, Malaysia, Singapore and Hong Kong. Damping-off of seedlings caused by Pythium sp. may occur, and occasionally Cercospora leaf-spot. Root knot nematodes (Meloidogyne spp.) may become troublesome in ratoon cropping. Caterpillars of Spodoptera litura and Diacrisia strigatula and aphids may cause serious damage. Chemical control is a general practice, regardless of the hazards of toxication.

List of Pests

This content is currently unavailable.

Notes on Natural Enemies

Waterhouse (1993) lists the following as major arthropod pests of I. aquatica grown as a crop in South East Asia: Acherontia lachesis, Agrius convolvuli, Agrotis ipsilon, Spodoptera litura, Aspidimorpha miliaris, Omphisa anastomosalis, Acanthocoris scaber and Aphis gossypii. Other insects associated with I. aquatica include Metriona circumdata [Cassida circumdata] (George and Venkataraman, 1987) and Tarophagus proserpina (Duatin and Pedro, 1986). Tarnished plant bug adults (Lygus rugulipennis) have been observed feeding on the succulent tissue where new leaves are developing in the leaf internodes (WorldCrops, 2018). An account is available of the various arthropod pest species associated with I. aquatica grown in concrete tanks in Florida over a three-year period (1978-1980) (Snyder et al., 1981).
Ipomoea aquatica is a host of the root-knot nematode Meloidogyne javanica in north-west Nigeria (Salawu et al., 1991), Meloidogyne hapla in Taiwan (Ruelo, 1980) and Paratrophurus sp. in the Ryukyu Islands (Teruya, 1979).
The snail Pomacea canaliculata has been reported to damage I. aquatica and other aquatic plants, including rice (Oryza sativa), taro (Colocasia esculenta), Nelumbo nucifera, Juncus decipiens, Cyperus monophyllus [Cyperus malaccensis subsp. monophyllus], Zizania latifolia [Z. caduciflora], Oenanthe stolonifera [O. javanica], Trapa bicornis [Trapa natans] and Azolla spp. This snail is also the intermediate host of the rat lungworm, which causes eosinophilic meningoencephalitis in humans in Taiwan and Japan (Mochida, 1991). In Thailand, I. aquatica and several other aquatic weeds are hosts of snails (Segmentina spp.) which transmit the parasite of humans, Fasciolopsis buski (Johannes, 1972).
Blister rust caused by Albugo ipomoeae-panduratae has been recorded on I. aquatica in Brunei where it is grown as a crop (Peregrine, 1974). White rust caused by Albugo ipomoeae-aquaticae has been reported wherever I. aquatica has been planted (e.g. China (Hong Kong, Fuzhou), India, Philippines, Singapore, Taiwan, Thailand, northern Australia, Irian Jaya) (Sawada, 1922; Safeeulla and Thrumalachar, 1953; Ho and Edie, 1969; Gao et al., 1985; Giri et al., 1989; Austin, 2007; Yu et al., 2015).
Fungi affecting I. aquatica include Phyllosticta ipomoeae, Cercospora ipomoeae [Passalora bataticola] and Pseudomonas syringae pv. syringae, which were observed in commercial greenhouses in Ontario and California during the 1990s (Cerkauskas et al., 2006); Stagonosporopsis cucurbitacearum (spot blight) in China (Liu et al., 2017); Myrothecium roridum (leaf spot) in China (Wang et al., 2017) and Ectophoma multirostrata (leaf spot) in Korea (Lee et al., 2022). Other species of fungi reported on I. aquatica include Colletotrichum sp., Fusarium sp., Phomopsis sp. (Suryanarayanan et al., 2018), Pseudocercosporella bakeri (David, 2000), Discosporella phaeochlorina and Mycosphaerella sp. (Ling, 1948).
In China, Xanthomonas perforans [Xanthomonas euvesicatoria pv. perforans] has been identified as the causal agent of bacterial leaf canker in I. aquatica, with Pantoea ananatis as a companion pathogen responsible for yellowing and brown rot of leaves (Hu et al., 2021).

Natural enemies

Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Acanthocoris scaberHerbivore
Plants|Stems
not specific  
Acherontia lachesis (death's head hawkmoth)Herbivore
Plants|Leaves
not specific  
Agrius convolvuli (convolvulus hawkmoth)Herbivore
Plants|Leaves
not specific  
Agrotis ipsilon (black cutworm)Herbivore
Plants|Leaves
not specific  
Albugo ipomoeae-aquaticaePathogen
Plants|Leaves
not specific  
Albugo ipomoeae-panduratae (white rust of sweet potato)Pathogen
Plants|Leaves
not specific  
Aphis gossypii (cotton aphid)Herbivore
Plants|Stems
not specific  
Aspidimorpha miliaris (spotted tortoise beetle)Herbivore
Plants|Leaves
not specific  
Cassida circumdataHerbivore
Plants|Leaves
not specific  
Colletotrichum sp.Pathogen
Plants|Leaves
not specific  
Discosporella phaeochlorinaPathogen
Plants|Leaves
not specific  
Ectophoma multirostrataPathogen
Plants|Leaves
not specific  
Fusarium sp.Pathogen
Plants|Leaves
not specific  
Lygus rugulipennis (bishop bug)Herbivore
Plants|Growing point
not specific  
Meloidogyne hapla (root knot nematode)Parasite
Plants|Roots
not specific  
Meloidogyne javanica (sugarcane eelworm)Parasite
Plants|Roots
not specific  
Mycosphaerella sp.Pathogen
Plants|Leaves
not specific  
Myrothecium roridum (blight: eggplant)Pathogen
Plants|Leaves
not specific  
Omphisa anastomosalis (sweet potato stem borer)Herbivore
Plants|Stems
not specific  
Pantoea ananatis (fruitlet rot of pineapple)Pathogen
Plants|Leaves
not specific  
Paratrophurus sp.Parasite
Plants|Roots
not specific  
Passalora bataticolaPathogen
Plants|Leaves
not specific  
Phomopsis sp.Pathogen
Plants|Leaves
not specific  
Phyllosticta ipomoeaePathogen
Plants|Leaves
not specific  
Pomacea canaliculata (invasive apple snail)Herbivore
Plants|Leaves
not specific  
Pseudocercosporella bakeriPathogen
Plants|Leaves
not specific  
Pseudomonas syringae pv. syringae (bacterial canker or blast (stone and pome fruits))Pathogen
Plants|Leaves
not specific  
Spodoptera litura (taro caterpillar)Herbivore
Plants|Leaves
not specific  
Stagonosporopsis cucurbitacearumPathogen
Plants|Leaves
not specific  
Tarophagus proserpina (taro planthopper)Herbivore
Plants|Leaves
not specific  
Xanthomonas euvesicatoria pv. perforans (bacterial spot of tomato)Pathogen
Plants|Leaves
not specific  

Impact Summary

CategoryImpact
Animal/plant collectionsNone
Animal/plant productsNone
Biodiversity (generally)Negative
Crop productionNegative
Environment (generally)Negative
Fisheries / aquacultureNegative
Forestry productionNone
Human healthNegative
Livestock productionNone
Native faunaNone
Native floraNegative
Rare/protected speciesNegative
TourismNone
Trade/international relationsNone
Transport/travelNegative

Impact

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).

Impact: Environmental

Impact on Habitats

As I. aquatica grows very rapidly, it can become a weed in some habitats (Parham, 1958; Varshney and Rzoska, 1976). In natural settings, such as rivers, shorelines and lakes, it may outcompete native vegetation and limit the use of these waters. It is considered a significant threat to Florida's waterways and wetlands (Westbrooks, 1989). Along waterways, the stems spread out over the water surface, forming a dense, tangled network that can obstruct water flow and access to it. 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).

Impact on Biodiversity

Impact studies are largely lacking in the literature (Gordon, 1998), but I. aquatica is known to form dense floating mats of intertwined stems over water surfaces, shading out native submerged plants and competing with native emergent aquatic plants (Langeland and Burks, 1998; Benson et al., 2001). Although this species has not invaded many areas in the USA, the areas where it does occur are located in areas of high conservation concern (Hawaiian Islands, Florida Everglades) (USDA-NRCS, 2018).

Impact: Social

Across bodies of freshwater, the long floating stems of I. aquatica form a dense network, which rise above the water surface and may impede water flow and navigation (Ashton, 1973). It is considered a serious threat to flood control (Westbrooks, 1989). I. aquatica is considered to be the second greatest problem plant in the Philippines, where it tends to overgrow freshwater marginal areas (Gangstadt, 1976).

Risk and Impact Factors

Invasiveness

Invasive in its native range
Proved invasive outside its native range
Highly adaptable to different environments
Has high reproductive potential
Has propagules that can remain viable for more than one year

Impact outcomes

Damaged ecosystem services
Ecosystem change/ habitat alteration
Negatively impacts agriculture
Negatively impacts tourism
Reduced amenity values
Reduced native biodiversity

Impact mechanisms

Competition - monopolizing resources
Pest and disease transmission

Likelihood of entry/control

Highly likely to be transported internationally deliberately
Difficult/costly to control

Uses

Economic Value

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, I. aquatica is cultivated as a vegetable along with other aquatic plants in the tropics (Roy and Chakrabarti, 2003;Flora of China Editorial Committee, 2018; PIER, 2018). It is widely traded in South East Asia as human food and as forage (Holm, et al., 1997; Flora of China Editorial Committee, 2018; USDA-ARS, 2018). It is cultivated in Bangladesh, Cambodia, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, New Guinea, Pakistan, Philippines, Sri Lanka, Thailand and Vietnam; as well as in Africa, Australia, the Pacific Islands and South America (Flora of China Editorial Committee, 2018).
The highly nutritious stems and leaves are eaten raw, boiled, stir fried, steamed, or pickled throughout Asia. The young tops or plants (stem and leaves) are cooked or lightly fried in oil and eaten in various dishes. 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).
In Thailand, Malaysia and Singapore, farmers' revenues from production of water spinach were reported to be US$0.05-0.40 per kg (Westphal, 1992).
Ipomoea aquatica may be fed to livestock, pigs, ducks and chickens (Brown, 1946; Westphal, 1992). The vines are used as fodder for cattle and pigs. In Malaysia, it is widely grown in fish ponds for feeding to pigs.

Social Benefit

According to the literature, I. aquatica has been used extensively as a medicinal plant (Flora of China Editorial Committee, 2018): as a mild laxative in India (Subramanyam, 1962); in the treatment of ringworm (Anon., 1959); and as a poultice in febrile delirium (Anon., 1959). I. aquatica is relatively rich in S-methyl methionine (vitamin U) and is used traditionally to treat gastric and intestinal disorders. Furthermore, it has been found to have insulin-like properties, acting as an anti-hyperglycaemic (Malalavidhane et al., 2000).

Environmental Services

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 species may be useful in removing nitrates from contaminated water, such as farm drainage and municipal waste (Snyder et al., 1981).

Uses List

Environmental > Host of pest
Medicinal, pharmaceutical > Traditional/folklore
Human food and beverage > Vegetable
Animal feed, fodder, forage > Fodder/animal feed

Detection and Inspection

To avoid further worldwide spread, shipments of seeds and spices from infested countries should be closely examined at the port of export or import for the presence of seeds of I. aquatica. Seed samples should be provided to plant regulatory inspectors to increase the effectiveness of the inspection. Many species of Ipomoea have brown or black, pubescent, 3-angled seeds with an omega-shaped border surrounding the hilum. Therefore, seeds alone should not be used for positive identification to species.

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Prevention

SPS Measures

Regulatory strategies to prevent the global movement and further establishment of exotic pest plants such as I. aquatica include foreign prevention (production of weed-free commodities for export to un-infested countries); exclusion (detection and mitigation of weed contaminants in imported products at ports of entry); detection, containment and eradication of incipient infestations, and cost-effective control of widespread species (Westbrooks, 1991).
Ipomoea aquatica is a Federal Noxious Weed in the USA, where it is illegal to import or transport it between states without a permit (USDA-APHIS, 2017). Since its listing, this species has been intercepted frequently at ports of entry (about 2500 times between 1981-1993) (Interceptions Records, USDA, Animal and Plant Health Inspection Service, Riverdale, Maryland, USA).
This species is classified in the Class I Prohibited Aquatic Plants List by the state of Florida, which makes its importation, transportation, non-nursery cultivation, possession and collection illegal in that state (Center for Aquatic and Invasive Plants, 2012; Hunsberger, 2001). However, registered nurseries are allowed to grow it for sale outside Florida, under a compliance agreement (Langeland et al., 2008), I. aquatica is still planted and sold illegally (D Schmitz, Florida Department of Environmental Protection, Tallahassee, Florida, USA, personal communication, 1995). In Texas, it is one of 13 prohibited aquatic weeds that are regulated by game wardens (L Fowler, USDA, Brownsville, Texas, USA, personal communication, 1995). It is listed as a noxious weed in Alabama, North Carolina, Vermont, and invasive in South Carolina and a prohibited species in Florida (USDA-NRCS, 2018). The California Department of Food and Agriculture views it as a crop and thus places no restrictions on its cultivation (R Westbrooks, USDA, Oxford, North Carolina, USA, personal communication, 1995).

Early Warning Systems

To avoid losses and costs of control, field surveys should be conducted to permit early detection and eradication of this noxious weed before it becomes firmly established on a new site.

Physical/Mechanical Control

Manual removal of I. aquatica from sites where it is regarded as a weed can only be successful if all plant parts with nodes are removed and destroyed. The objective is to prevent re-growth and further seed production. In an experimental study conducted in north central India, I. aquatica died when clipped underwater (Middleton, 1990). Mechanical clearance using rakes and chains is often uneconomical (Beshir, 1978). However, complete eradication by manual means is not practical (Chin and Fong, 1978).

Biological Control

The tortoise beetle (Metriona circumdata [Cassida circumdata]) is used as a biological control agent for I. aquatica in Keoladeo National Park, Bharatput, India. Grubs feed on the underside of the leaves and skeletonize them completely (George and Venkataraman, 1987). It would appear that biological control has not been attempted in its non-native habitats (PIER, 2018).

Chemical Control

In pot experiments in India, paraquat was effective in completely killing I. aquatica (Misra and Tripathy, 1975). In field trials conducted during 1988-1989 at Maruteru, India, 2,4-D, paraquat and urea were evaluated (singly and in combination) for the control of I. aquatica in drainage canals. All treatments reduced weed biomass production, reduced weed growth by 18-99% and reduced re-sprouting of I. aquatica from pretreatment values of 100% to 1.4-65.3%. Paraquat + 2,4-D resulted in the greatest decrease in weed growth and re-sprouting (Raju and Reddy, 1993).
In a study conducted at the Itoikin Rice Irrigation Project in Nigeria, in January-February 1989, application of 2,4-D, diquat with and without a wetting agent, ioxynil + 2,4-D, paraquat or terbutryn resulted in mortality of I. aquatica 8 weeks after treatment (Akinyemiju and Bewaji, 1990).
Application of thiobencarb post-emergence, butachlor pre-emergence, or oxadiazon has been discussed as part of an integrated approach for controlling grass weeds, sedges and broadleaved weeds (including I. aquatica) in rice (Shad, 1986).
Post-emergence herbicides were evaluated in transplanted rice in the irrigated basin of River Mombo in northern Tanzania. Bentazone + propanil gave the best weed control and hand-weeding was next best. Butachlor, benfuresate and molinate herbicides have no effects whatsoever. The quality or yield of grain was not affected by herbicide application (Ritoine et al., 1981). Aquatic herbicides have been successful as a control measure but results are often only temporary (Ninomiya et al., 2003), requiring repeated application; more research needs to be undertaken on the effectiveness of 2,4-D, which is a far more selective herbicide (PIER, 2018).
Regulatory Treatments

Microwave Energy

Small quantities of I. aquatica seeds needed for seed collections and other uses can be killed by exposure to microwave radiation (700 watts) for 5 min. Seeds should be placed on moistened filter paper or paper towels in a covered beaker. Steam created from the paper creates a high-humidity environment that helps to prevent scorching of the seed surface (Westbrooks and Eplee, 1989).

Dry Heat

The seeds can be killed by exposure to dry heat at a temperature of 121°C for 15 min.

Moist Heat

Seeds of the closely related species I. triloba can be killed by exposure to moist heat (hot water) at a temperature of 92°C for 40 min (R Westbrooks, USDA, Whiteville, North Carolina, USA, unpublished data, 1995).

Agronomic Aspects

Kangkong can be grown in various ways. In Malaysia, Taiwan, Thailand and Vietnam, it is usually cultivated as an upland crop (e.g. the 'Chinese market-gardening system' or the 'ditch-and-dike system' in Thailand), but in Indonesia it is mainly grown in water (e.g. 'paddy-field kangkong' or 'floating kangkong').

Upland or dry cultivation

Under these conditions kangkong roots in soils which are not inundated. Seeds are either broadcast or sown in rows (in Malaysia,Singapore and Thailand). In Thailand, the seeds are sometimes soaked for 12-24 hours in water before sowing, but in the leading production areas, soaking is not practised. When seeds of reliable quality are available, Thai farmers use about 80 kg/ha. If necessary, soils are limed before sowing (2500 kg/ha). Besides seed, cuttings are used for propagation in China and Taiwan. Cropping takes place on beds. Plant densities may vary between 30-170 plants/m2. A quick and uniform emergence is an important consideration for farmers.

Paddy-field or wet cultivation

Paddy-field kangkong is practised in Indonesia, the Philippines, Thailand, China,Taiwan, Hong Kong and India. Planting may be direct by cuttings or by transplanting 6-week-old seedlings raised on nursery beds (in China, Taiwan and Hong Kong). Planting densities may vary widely from 200*000-1*500*000 cuttings or seedlings per ha. Floating kangkong is mainly grown on a commercial scale in ponds and rivers in Thailand, China and Taiwan. Integrated systems with fish, kangkong, pigs and chickens are practised. There is no root contact with the soil. Cuttings are anchored in the water by bamboo sticks forming a kind of bed.

Husbandry

Upland cultivation. Weeding and watering are normally done by hand. Chicken, duck and pig manure are used as a basic application in Thailand, Malaysia and Singapore. Night soil is no longer permitted as manure in these countries. Fertilizers (e.g. ammonium sulphate, urea) are used as a top dressing immediately after sowing and 10-15 days later. In China, night soil is the most important fertilizer for kangkong. Application of higher levels of nitrogen fertilizer does not solely increase yields; leaf/stem ratios and dry matter content, especially of stems and petioles, decrease while nitrate content increases. Therefore, the amount of nitrogen available in the soil plus that provided as fertilizers should be monitored to avoid unacceptably high amounts of nitrate in the produce.

Paddy-field cultivation

The water level is raised according to the development of the crop. Young plants cannot withstand flooding. In China and Hong Kong, night soil is applied diluted with irrigation water. In Taiwan, a basic application of 10 t/ha of cow dung is followed by a top dressing of 50 kg/ha of ammonium sulphate after each harvest. In the Bangkok area, about 300 kg of NPK fertilizer is commonly applied twice a month. In Indonesia, farmers apply 150-300 kg/ha of urea after each harvest. Cultivation is terminated in the event of low temperatures in 'winter' (in China, Taiwan and Hong Kong), flowering (in Thailand), or serious disease, pest or weed problems.

Harvesting

Consumers have specific preferences with regard to the quality of the product, e.g. number of leaves, stem length, percentage of fibre, taste. - Upland cultivation. Harvest takes place from 20-50 days after sowing. In Thailand, Malaysia, Singapore, Taiwan and China, uprooting the plants 20-30 days after sowing is common practice. The stems of these seedlings are big and tender but crisp. Ratooning is only practised in home gardens.

Cultivation

Two methods of cultivation are used: dry and wet. In both cases, large amounts of organic material and plenty of water are required to achieve adequate yields. Heavy fertilizing benefits leafy growth. Weed control is mostly done manually. In Malaysia, Taiwan, Thailand and Vietnam, it is usually cultivated as an upland crop (e.g. the 'Chinese market-gardening system' or the 'ditch-and-dike system' in Thailand), but in Indonesia it is mainly grown in water (e.g. 'paddy-field kangkong' or 'floating kangkong').
Dry (upland) cultivation The plants are usually planted on raised beds, at a spacing of 15 cm, and often supported by trellises. Under these conditions the plant roots in soils which are not inundated. Seeds are either broadcast or sown in rows (in Malaysia, Singapore and Thailand). In Thailand the seeds are sometimes soaked for 12-24 hours in water before sowing, but in the leading production areas, soaking is not practised. When seeds of reliable quality are available, Thai farmers use about 80 kg/ha. If necessary, soils are limed before sowing (2500 kg/ha). Besides seed, cuttings are used for propagation in China and Taiwan. Cropping takes place on beds. Plant densities may vary between 30 and 170 plants/m2. A quick and uniform emergence is an important consideration for farmers. Weeding and watering are normally done by hand. Chicken, duck and pig manure are used as a basic application in Thailand, Malaysia and Singapore. Night soil is no longer permitted as manure in these countries. Fertilizers (e.g. ammonium sulfate, urea) are used as a top dressing immediately after sowing and 10-15 days later. In China, night soil is the most important fertilizer for kangkong. Application of higher levels of nitrogen fertilizer does not solely increase yields;leaf/stem ratios and dry matter content, especially of stems and petioles, decrease while nitrate content increases. Therefore, the amount of nitrogen available in the soil plus that provided as fertilizers should be monitored to avoid unacceptably high amounts of nitrate in the produce.
Wet (paddy-field) cultivationIn wet cultivation, usually about 30-cm-long cuttings are planted in mud. As the vines grow, the field is flooded and a continuous slow flow of water is required. In wet cultivation, weeds are controlled by the flooding. Paddy-field kangkong is practised in Indonesia, the Philippines, Thailand, China,Taiwan, Hong Kong and India. Planting may be direct by cuttings or by transplanting 6-week-old seedlings raised on nursery beds (in China, Taiwan and Hong Kong). Planting densities may vary widely from 200,000 to 1,500,000 cuttings or seedlings per ha. Floating kangkong is mainly grown on a commercial scale in ponds and rivers in Thailand, China and Taiwan. Integrated systems with fish, kangkong, pigs and chickens are practised. There is no root contact with the soil. Cuttings are anchored in the water by bamboo sticks forming a kind of bed. The water level is raised according to the development of the crop. Young plants cannot withstand flooding. In China and Hong Kong night soil is applied diluted with irrigation water. In Taiwan, a basic application of 10 t/ha of cow dung is followed by a top dressing of 50 kg/ha of ammonium sulfate after each harvest. In the Bangkok area about 300 kg of NPK fertilizer is commonly applied twice a month. In Indonesia farmers apply 150-300 kg/ha of urea after each harvest. Cultivation is terminated in the event of low temperatures in 'winter' (in China, Taiwan and Hong Kong), flowering (in Thailand), or serious disease, pest or weed problems.

Harvesting

Harvesting can start 30-40 days after sowing. Yields vary greatly; in dry cultivation annual yields of around 40 t of fresh product per hectare are reported. In wet cultivation, yield can be up to 100 t/ha. World production statistics are not available.
Consumers have specific preferences with regard to the quality of the product, e.g. number of leaves, stem length, percentage of fibre, taste. In upland cultivation harvest takes place from 20 to 50 days after sowing. In Thailand, Malaysia, Singapore, Taiwan and China, uprooting the plants 20-30 days after sowing is common practice. The stems of these seedlings are big and tender but crisp. Ratooning is only practised in home gardens (Elzebroek and Wind, 2008).

Genetic Resources and Breeding

Germplasm is available at the Asian Vegetable Research and Development Center (AVRDC) in Taiwan and at national research institutes in South-East Asia. A collection of at least 50 landraces of kangkong is available at the Kasetsart University in Bangkok (Thailand).
Not much breeding work has been carried out on the crop in South-East Asia. A seed company in Thailand has selected some superior cultivars (Elzebroek and Wind, 2008).

Major Cultivars

Two types of cultivars can be determined, with many cultivars of each: (1) the red type with red-purple stems, dark-green leaves and pink to lilac flowers; and (2) the green type with whitish-green stems, green leaves and white flowers (Elzebroek and Wind, 2008).

Propagation

Ipomoea aquatica is propagated from seed or stem cuttings, usually germinated and grown in nursery beds first (Elzebroek and Wind, 2008).

Nutritional Value

Fresh leaves and tops contain approximately 90% water, 3% protein, 5% carbohydrates, 1% fibre, 0.3% fat and 1.6% ash, the minerals Ca, Mg and Fe, and vitamin C and provitamin A (Elzebroek and Wind, 2008). 

Production and Trade

Production figures are difficult to obtain due to the lack of any registration of information on production and trade. In Thailand and Malaysia white-flowering kangkong is the second most widely grown leafy vegetable after pak choi (Brassica rapa cv. group Pak Choi). Red kangkong is collected from the wild and consumed in rural areas of Malaysia, but in Thailand and Singapore, it is sometimes sold in the markets as well. In Indonesia, the harvested area is estimated at 10,000 ha (1988), mainly of paddy-field kangkong, planted by stem cuttings and harvested by monthly ratooning during nine months of the year. In Malaysia, the area under cultivation is estimated to be 600-1100 ha with a total production of 60,000-220,000 t/year. Marketing in Thailand, Malaysia and Singapore is usually done by middlemen. Kangkong is exported from Bangkok to Hong Kong and to a lesser extent to European countries. Kangkong seed is produced on a commercial scale in Hong Kong, China, Taiwan, Thailand, the Philippines and Japan. In Malaysia, 20% of kangkong farmers grow their own seed. Thailand is the leading seed producer of the region with 700-900 t per year, of which about 500 t is exported to neighbouring countries. The bulk of the seed is still landrace Phakbung-chin produced by paddy farmers in Nakhon Pathom Province as an additional cash crop. The seed trade in Malaysia and Singapore is not well organized. Chinese middlemen import seed from Thailand and Taiwan. Malaysia imports about 180 t of seed annually.

Prospects

Gradually the seed-propagated upland kangkong will become more important at the expense of the vegetatively propagated paddy-field kangkong. Research should focus on the improvement of cultural practices, especially regarding fertilizer application and control of insect damage. Breeding efforts should concentrate on obtaining productive cultivars with acceptable quality that are well adapted to specific environments and resistant to white rust.

Links to Websites

NameURLComment
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.
Global register of Introduced and Invasive species (GRIIS)http://griis.org/Data source for updated system data added to species habitat list.

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