Ipomoea aquatica, commonly known as water spinach or kangkung, is a semi-aquatic plant, tropical plant grown as a vegetable for its tender shoots. I. aquatica is generally believed to have been first domesticated in Southeast Asia. It is widely cultivated in Southeast Asia, East Asia, and South Asia. It grows abundantly near waterways and requires little to no care.
Description
Ipomoea aquatica grows in water or on moist soil. Its stems are or longer, rooting at the nodes. The hollow cavity within the stem makes the plant buoyant. The leaves vary from typically sagittate (arrowhead-shaped) to
lanceolate, long and broad. The flowers are trumpet-shaped, in diameter, and usually white in colour with a mauve centre. Propagation is either by planting cuttings of the stem shoots, which will root along nodes, or by planting the seeds from flowers that produce seed pods.
Names
Ipomoea aquatica is most widely known as kangkong (also spelled
kangkung), its common name in Maritime Southeast Asia, which likely originates from either
Malay language or one of the languages of the Philippines.
It is also known as water spinach, river spinach, water morning glory, water convolvulus, or by the more ambiguous names Chinese spinach, Chinese watercress, Chinese convolvulus or swamp cabbage. It is known as (空心菜) in Mandarin, (蕹菜) in
Cantonese and in Hawaii, and (通菜) in modern Cantonese.
Origin and distribution
The origin of
Ipomoea aquatica is not quite clear, but it is generally believed to be native to
Southeast Asia and was first cultivated there. This is supported by phylogenetic studies, its ideal climatic conditions, and the number of native pathogens in the region (like
Albugo spp.); as well as its predominant cultivation range, the prevalence in usage as food and traditional medicine, and the number of distinct native names in Southeast Asian languages and language families.
[Li, H.-L. 1970. The origin of cultivated plants in Southeast Asia. Economic Botany 24:3-19.]
Several sources have also cited China or India as the location of the plant's domestication.[Purseglove, J.W. 1968. Tropical Crops. Dicotyledons 1. Longmans, Green and Co. Ltd., London.][Filatenko, A.A., K. Pistrick, H. Knüpffer & K. Hammer. 2003. E.N. Sinskaya’s inventory of plant taxa in the basic and dependent areas of the historical development of the flora of cultivated plants. Pp. 222-256 in Rudolf Mansfeld and Plant Genetic Resources. Proceedings of a Symposium dedicated to the 100th Birthday of Rudolf Mansfeld, Gatersleben, Germany, 8–9 October 2001. Edited by H. Knüpffer & J. Ochsmann. Schriften zu Genetischen Res- sourcen, Band 22, Zentralstelle für Agrardokumnetation und Information (ZADI), Informationszentrum Biologische Vielfait (IBV), Bonn, Germany.][Chang, K-C. 1970. Beginnings of agriculture in the Far East. Antiquity 44:1-12.][Westphal, E. 1993. Ipomoea aquatica Forsskal Pp. 181- 184 in Plant Resources in South-East Asia. Number 8. Vegetables. Edited by J.S. Siemonsma & K. Piluek. Pu-doc Scientific Publishers, Wageningen.][Owens, G. 2003. Kangkong Fact Sheet. www.nt.gov.au/ dpifm.][Van Wyk, B.-E. 2005. Food Plants of the World. An Illustrated Guide. Timber Press, Inc., Portland, Oregon.] However, these claims have no supporting evidence other than the appearance of the plant's name in historical records. The first clear mention of I. aquatica in Chinese records is in the Nanfang Caomu Zhuang written by the Chinese botanist Ji Han (AD 263-307). Ji Han specifically identifies I. aquatica as being "a strange vegetable of the south" with a foreign origin brought over by "western countries". The claim for an Indian origin is based on the presence of the old name kalamba for the plant in Sanskrit, presumed to be from around 200 BC, but this is putative.
Ipomoea aquatica is also found in Africa, the southwestern Pacific Islands, and northern Australia. However, in Africa and the Pacific Islands, the number of native common names isn't as varied as in Southeast Asia, and there are very few references to the local use of I. aquatica for any purpose. Similarly, in Australia, it does not have indigenous names at all and is entirely absent in the traditional diet of Indigenous Australians. These imply that I. aquatica weren't native to these regions and were likely introduced relatively late from tropical Asia.
Composition
Nutrition
Safety
Health risk
Many of the waters where water spinach grows are fed by domestic or other waste. Pigs in southeast Asia are a natural reservoir for the parasite
Fasciolopsis. Infections in the
Mekong regions resulted from feeding on water spinach. Infections of
F. buski in humans through water spinach can be anticipated. The infection can be prevented by proper preparation such as frying or boiling.
[Yoshihara, S., Hung, N. P., Hung, N. H., Loc, C. B. "Helminths and Helminthiosis of Pigs in the Mekong Delta, Vietnam with Special Reference to Ascariosis and Fasciolopsis buski Infection." Jarq 33, 193-199 (1999)] Contamination with thermotolerant coliforms (ThC) or
Protozoa with fecal origin, are very likely when the water spinach is planted in wastewater fed urban systems.
[Vuong TA, Nguyen TT, Klank LT, Phung DC, Dalsgaard A."Faecal and protozoan parasite contamination of water spinach (Ipomoea aquatica) cultivated in urban wastewater in Phnom Penh, Cambodia." Tropical Medicine and International Health, 73-81 (2007)] Water spinach has great potential as a purifier of aquatic habitats. It is an efficient accumulator of
cadmium,
lead, and mercury. This characteristic can be dangerous if water spinach is planted for human or animal feed in polluted aquatic systems. Mercury in water spinach is composed mostly as
methylmercury and has the highest potential of becoming a threat to human health. The edible parts of the plant have a lower
Heavy metals concentration. The stems and bottom of the edible portion of the plant are higher in concentration and should be removed to minimize the heavy metal intake.
[Gosh, S. "Wetland Macrophytes as toxic metal accumulators" International Journal of Environmental Sciences, 523-528 (2010)][Göthberg A., Greger, M., Bengtsson, E. "Accumulation of heavy metals in water spinach (Ipomoea aquatica) cultivated in the Bangkok region, Thailand" Environmental Toxicology, 1934-1939 (2009)]
Uses
Culinary
The vegetable is a common ingredient in East, South and Southeast Asian dishes, such as in stir-fried water spinach.
In
Singapore,
Indonesia, and
Malaysia, the tender shoots along with the leaves are usually
stir frying with
chili pepper,
garlic,
ginger, dried
shrimp paste (
belacan/
terasi) and other
. In
Penang and
Ipoh, it is cooked with
cuttlefish and a sweet and spicy sauce. Also known as eng chhai in the Hokkien dialect, it can also be boiled with preserved cuttlefish, then rinsed and mixed with spicy rojak paste to become jiu hu eng chhai. Boiled eng chhai also can be served with fermented krill noodles – belacan bihun – and prawn mi.
In Burmese cuisine, water spinach is the primary ingredient in a Burmese salads called gazun ywet thoke (ကန်စွန်းရွက်သုပ်), made with blanched water spinach, lime juice, fried garlic and garlic oil, roasted rice flour and dried shrimp.
In Indonesian cuisine it is called kangkung; boiled or blanched together with other vegetables it forms the ingredient of gado-gado or pecel salads in peanut sauce. Some recipes that use kangkung include plecing kangkung from Lombok, mie kangkung (kangkong noodles) from Jakarta, and petis kangkung from Semarang.
In Thailand, where it is called phak bung (), it is eaten raw, often along with som tam or nam phrik, in stir-fries and in curries such as kaeng som.
In the Philippines, where it is called kangkóng, the tender shoots are cut into segments and cooked, together with the leaves, in fish and meat stews, such as sinigang. The vegetable is also commonly eaten alone. In Philippine adobo (also called apan-apan), it is sautéed in cooking oil, , garlic, vinegar, and soy sauce.
In Chinese cuisine, Ipomoea aquatica is a popular leafy vegetable commonly stir-fried with garlic, fermented tofu, or chili, depending on regional preferences. It is particularly associated with southern China, including Guangdong and Fujian, where it is often prepared as a quick, flavorful dish. In Sichuan cuisine, it may be stir-fried with pickled chili for a spicy twist. In Taiwan, it is cooked similar to Southeast Asia, with soy sauce and dried shrimp for added umami.
File:Adobong kangkong (Philippines).jpg|Filipino Philippine adobo
File:Ensaladang kangkong.jpg|Filipino Kinilaw
File:Pelecing kangkung.JPG| Indonesian plecing kangkung from Lombok
File:Mie Kangkung.JPG|Indonesian mie kangkung (with noodles)
File:Gendar Petis Kangkung.jpg|Indonesian petis kangkung (with gendar rice cake) from Semarang
File:Kangkungblacan.jpg|-style kangkung belacan
File:Pak boong fai daeng.jpg|Thailand phak bung fai daeng
Phytoremediation
Using aquatic macrophytes to remove nutrients from wastewater and to control freshwater
eutrophication has been reported to be a feasible way of
phytoremediation. Various plants, including
I. aquatica, have been tested for this use. Owing to its being edible and thus marketable, it could be an attractive option for this use.
[Li, M., Wu, Y. J., Yu, Z. L., Sheng, G. P., & Yu, H. Q. (2007). Nitrogen removal from eutrophic water by floating-bed-grown water spinach (Ipomoea aquatica Forsk.) with ion implantation. Water research, 41(14), 3152-3158.]
Animal feed
Water spinach is fed to livestock as green fodder with high nutritive value—especially the leaves, for they are a good source of carotene. It is fed to cattle, pigs, fish, ducks, and chicken.
[Pandey, A.K. Aquatic Vegetables. Udaipur: Agrotech Academy, 2011. Print.] In limited quantities,
I. aquatica can have a somewhat laxative effect.
Medicinal
I. aquatica is used in the traditional medicine of southeast Asia and in the traditional medicine of some countries in Africa. In southeast Asian medicine it is used against
piles, and
nosebleeds, as an
anthelmintic, and to treat high blood pressure. In Ayurveda, leaf extracts are used against jaundice and nervous debility.
In indigenous medicine in Sri Lanka, water spinach is supposed to have insulin-like properties.
Christophe Wiart cites several promising studies showing improvements in blood glucose levels in humans and rats and concludes that clinical trials are warranted.
Antioxidant bioactive compounds and anti-microbial substances can be detected in water spinach.
Cultivation
Ipomoea aquatica is most commonly grown in east, south, and southeast Asia. It flourishes naturally in waterways, and requires little if any care. It is used extensively in Indonesian, Burmese, Thai, Lao, Cambodian, Malay, Vietnamese, Filipino, and Chinese cuisine, especially in rural or
kampung (village) areas. The vegetable is also extremely popular in
Taiwan, where it grows well. During the Japanese occupation of Singapore in World War II, the vegetable grew remarkably easily in many areas, and became a popular wartime crop.
Water spinach has been found to be cultivated in the following countries:[Pinker, I., U. Bubner, and M. Böhme. "Selection of water spinach (Ipomoea aquatica Forssk.)-genotypes for protected cultivation in temperate regions." I International Conference on Indigenous Vegetables and Legumes. Prospectus for Fighting Poverty, Hunger and Malnutrition 752. 2006.]
In the United States, it is cultivated in California, Florida, Hawaii, Texas, Arizona, and the U.S. Virgin Islands.[Chilton, Earl W. "Risk Assessment for Water Spinach (Ipomoea Aquatica) in Texas." Journal Of Aquatic Plant Management 55 (2017): 96-102. Web.] It is also found in Africa and in its wild form; it is collected and used by the Shambaa people people in Tanzania.[Austin, Daniel F. F. "Water Spinach (Ipomoea Aquatica, Convolvulaceae) a Food Gone Wild." Ethnobotany Research and Applications 5 (2007): 123-46. Web.][Vainio-Mattila, Katariina. "Wild vegetables used by the Sambaa in the Usambara Mountains, NE Tanzania." Annales Botanici Fennici. Finnish Zoological and Botanical Publishing Board, 2000.]
Water spinach is also potentially suitable for cultivation in in more temperate regions.
In non-tropical areas, it is easily grown in containers given enough water in a bright sunny location. It readily roots from cuttings.
Requirements for climate and soil
Water spinach is ideal for
Subtropics-tropical and
Tropics climate, as it does not grow well below and is sensitive to frost. High soil moisture is beneficial for growth. Clay soils and
soils rich in organic matter are suitable for water spinach. The ideal pH range for the growth is from 5 to 7. The provision of shade has been shown to have a positive influence on the yield of water spinach.
Traditional cultivation methods
Water spinach is cultivated in a variety of systems. In
Hong Kong, two methods are traditionally used: the dryland method and the wetland method.
In the dryland method, water spinach is grown on raised beds which are separated by irrigation ditches. The seeds can be sown directly onto the beds. Alternatively, a nursery may be used and the seedlings are transplanted when they reach a sufficient size. In either case, the distance between the plants should be about by the time they are tall. Regular irrigation is crucial in the dryland system and so is sufficient fertilization. Water spinach cultivated with the dryland method is ready for harvest 50 to 60 days after sowing. Harvesting is done by pulling up the whole plant.[Edie, Harry, and H. Ho. "Ipomoea Aquatica as a Vegetable Crop in Hong Kong." Economic Botany 23.1 (1969): 32-36. Web.]
The wetland method is the traditionally more common and important method for cultivation in Hong Kong: In the wetland method, water spinach is cultivated on flat fields surrounded by raised banks, which have oftentimes been used as Paddy field in the past. These former rice paddies have a heavy clay soil with an iron-pan. This helps to retain water for the water spinach. The seedlings to be used in this method are usually grown in a nursery on a dry field, as germination under water is quite poor. Six weeks after sowing, cuttings can be taken from the seedlings for transplantation. One cutting is an approximately long cut from the stem containing seven or eight nodes. This is then planted in the field with a spacing of about . The field is prepared beforehand by flooding it to a depth of . The soil itself is tramped into a liquid mud so that the cuttings can root easily. Once the plants are established, the depth of the flooding is increased to . The first harvest in the wetland method can usually be done at around 30 days after transplantation. Also, the harvesting differs from the dryland system: In the wetland, the upper part of the main shoot is cut at about water level. This stimulates lateral growth and produces horizontal shoots carrying vertical branches. After the first harvests, every seven to ten days throughout the summer, these vertical branches can be harvested. After the planting period, the fields are drained and once the fruit of the water spinach is ripe, it is harvested, dried, then trodden to release the seeds which are to be used for the following season.
Use of fertilizer
How much fertilizer is used for the cultivation strongly depends on the region. Most research is from the 1980s and 1990s. Generally, it has been shown that a dose of
Nitrogen/ha is sufficient and that the application of
Potassium can be beneficial on the yield. Also, the application of plant growth regulators, for example
Adenine and Zetanine, has been found to be an effective means to promote water spinach growth. One study has determined, that the highest yields are produced with the application of 60 kg/ha of N, 90 kg/ha of P
2O
5 and 50 kg/ha of
Potassium oxide for the first harvest. For the second harvest the optimal fertilization was determined as 120 kg/ha of N, 45 kg/ha of P
2O
5 and 100 kg/ha of K
2O.
Taiwan: In Taiwan, the usual fertilization includes the basic application of about 10 t/ha of cow manure followed by 50 kg/ha of ammonium sulfate after each harvest.
Bangkok: In Bangkok, it is common to apply about 300 kg/ha of NPK fertilizer twice a month.
Indonesia: In Indonesia, usually 150 kg to 300 kg of NPK are applied per hectare.
Pathogens and pests
There are several pathogens and pests reported, affecting
I. aquatica. Pathogens include
Pythium, causing problems like damping-off,
Cercospora leaf spot and root nematodes.
Also,
may be problems in fields. Additionally, there are several polyphagous insects feeding on
I. aquatica.
Lepidoptera species include
Diacrisia strigatula Walker and
Spodoptera litura. The "woolly-bear" caterpillars (
D. virginica Fabricius) of the eastern United States and
D. strigatula (Chinese tiger moth) are other species with wide food preferences.
A specialist pathogen on
I. aquatica is the
oomycete Albugo ipomoeae-aquaticae, though its range is restricted to southern and southeast Asia.
Invasiveness
Ipomoea aquatica is listed by the
USDA as a noxious weed,
especially in the states of
Florida,
California, and
Hawaii, where it can be observed growing in the wild.
In the US, water spinach has mainly become a problem in Florida. It is unclear why it is a problem there; however, although the fast growth rate has been cited as a threat to native plants in certain areas of Florida.
It could be owing to the time since introduction, or owing to climatic factors.
has been extensively cultivated in
Texas for over 30 years, having been originally brought there by Asian immigrants. Because no evidence indicates the plant has escaped into the wild, Texas lifted its ban on cultivation for personal use with no restrictions or requirements, noting its importance as a vegetable in many cultures, and also began permitting cultivation for commercial sales with the requirement of an exotic species permit.
Possession of
I. aquatica has been prohibited in Florida since 1973, but it is still being grown and sold illegally. Some of the infestations in Florida public lakes have been eradicated, or at least attempts have been made.
[Langeland, K.A. & K.C. Burks. 1998. Editors of Identification & Biology of Non-Native Plants in Florida's Natural Areas. University of Florida, Gainesville] In
Sri Lanka it invades wetlands, where its long, floating stems form dense mats which can block the flow of water and prevent the passage of boats.
[Gunasekera Lalith. Invasive Plants, A Guide to the Identification of the Most Invasive Plants in Sri Lanka, Colombo 2009.]
Gallery
File:04657jfDampol Rueda Plaridel Pungo Calumpit Bulacan Riverbanks Kangkung Viaductfvf 26.jpg| I. aquatica along the Angat River, Philippines
File:Starr-121029-0421-Ipomoea aquatica-habit in wetland-Ukumehame-Maui (24827090269).jpg| Ipomoea aquatica in Ukumehame, Maui, Hawaii
File:Immature seeds of Ipomoea aquatica 2.jpg|Immature fruits of Ipomoea aquatica
File:Ipomoea aquatica Nksw 4.jpg| Ipomoea aquatica at Nakhonsawan school, Nakhon Sawan, Thailand
File:Ipomoea aquatica bd-3.jpg|Fruits of Ipomoea aquatica
File:Ipomoea aquatica (Marsh Glory) flower W IMG 0403.jpg|Close-up of I. aquatica flower in Hyderabad, India
File:9916Wawa Poblacion Balagtas 13.jpg|Freshly-harvested I. aquatica bundles being unloaded from rafts in the Philippines
File:甕菜 Ipomoea aquatica -香港西貢獅子會自然教育中心 Saikung, Hong Kong- (9240155912).jpg| I. aquatica with white flowers in Sai Kung, Hong Kong
File:Bubulcus ibis in the Philippines 22.jpg| among I. aquatica in Norzagaray, Philippines
File:HK WCD 灣仔 Wan Chai 春園街 Spring Garden Lane shop Kai Bo Food Supermarket vegetable July 2021 SS2.jpg| I. aquatica being sold in a market in Hong Kong
File:Ipomoea aquatica.jpg| I. aquatica bundles sold in a market in Sarawak, Malaysia
File:03899jfPasig City Boundary Buting Bridge School Creek Monument Makati Cityfvf 19.jpg|Bundles of I. aquatica being sold by a roadside vendor in Makati City, Philippines
See also
-
Stir-fried water spinach
-
List of vegetables
-
Sweet potato ( Ipomoea batatas), another edible species in the morning glory family
External links
