Difference between revisions of "Watercress" - New World Encyclopedia

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{{Taxobox
 
{{Taxobox
 
| name = Watercress
 
| name = Watercress
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| subdivision_ranks = [[Species]]
 
| subdivision_ranks = [[Species]]
 
| subdivision =  
 
| subdivision =  
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''Nasturtium microphyllum'' (Boenn.) Rchb.<br>
 
 
''Nasturtium officinale'' W.T. Aiton
 
''Nasturtium officinale'' W.T. Aiton
 +
''Nasturtium microphyllum'' Boenn. ex Rchb. <br/>
 
}}
 
}}
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'''Watercress''' is the common name for a fast-growing, aquatic or semi-aquatic [[perennial plant]], ''Nasturtium officinale'' (formerly ''Rorippa nasturtium-aquaticum'') of the mustard (or cabbage) family [[Brassicaceae]], characterized by hollow stems, pinnately compound leaves, and small flowers. and one of the oldest known [[leaf vegetable]]s consumed by human beings. These [[plant]]s are members of the Family [[Brassicaceae]] or  [[cabbage]] family, botanically related to [[garden cress]] and [[Mustard plant|mustard]] &mdash; all noteworthy for a peppery, tangy flavour.  
+
'''Watercress''' is the common name for a fast-growing, aquatic or semi-aquatic, [[herbaceous]], [[perennial plant]], ''Nasturtium officinale'' (formerly ''Rorippa nasturtium-aquaticum'') of the [[mustard]] family [[Brassicaceae]], characterized by hollow stems, [[pinnate]]ly compound [[leaf|leaves]], and small [[flower]]s. The term also is used for a similar and closely related plant, ''Nasturtium microphyllum'' (formerly ''Rorippa microphylla''), which is sometimes listed as ''Nasturtium officinale var. microphyllum'' and commonly known as onerow yellowcress (USDA 2008; PFAF 2000). ''N. officinale'' is sometimes referred to as "green watercress," with ''N. microphyllum'' referenced as brown or winter watercress (Bender and Bender 2005).
 +
 
 +
Watercress is among the oldest known [[leaf vegetable]]s consumed by [[human being]]s. These two [[species]] are botanically related to [[garden cress]] and [[Mustard plant|mustard]]&mdash;all noteworthy for a peppery, tangy flavor. Added to salads, soups, or sandwiches, or used as a garnish, watercress provides a nutritious addition to food, while its pungent, peppery flavor adds to the culinary experience.
  
 
==Description==
 
==Description==
−
''Brassicaceae''' or '''Cruciferae''', also known as the '''crucifers''', the '''mustard family''' or '''cabbage family''' is a [[Family (biology)|family]] (the third lowest primary [[taxonomic rank]]) of flowering plants ([[Angiospermae]]). The name Brassicaceae is derived from the included [[genus]] ''[[Brassica]]''. '''Cruciferae''' is an older name, it means "cross-bearing", because the four [[petal]]s of their flowers are reminiscent of a [[cross]]. According to [[ICBN]] Art. 18.5 (Vienna Code) both ''Cruciferae'' and ''Brassicaceae'' are regarded as validly published, and are thus accepted as names for the family.
+
The two species of watercress belong to the [[flowering plant]] family '''Brassicaceae''' (or Cruciferae), also known as the crucifers, the [[mustard]] family, or the cabbage family. (Cruciferae is an older name for the family. It means "cross-bearing," because the four [[petal]]s of their flowers are reminiscent of a [[cross]].)  
−
 
 
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It contains over 330 [[genus|genera]] and about 3,700 [[species]], according to the [[Royal Botanic Gardens, Kew]]. The largest genera are ''[[Draba]]'' (365 species), ''[[Cardamine]]'' (200 species, but its definition is controversial), ''[[Erysimum]]'' (225 species), ''[[Lepidium]]'' (230 species) and ''[[Alyssum]]'' (195 species.)
 
−
 
 
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The family contains well-known species like ''[[Brassica oleracea]]'' (cabbage, cauliflower...), ''[[Brassica rapa]]'' (turnip, Chinese cabbage...), ''[[Brassica napus]]'' (rapeseed...), ''[[Matthiola]]'' (stock) and many other.
 
−
 
 
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The family consists only of [[herbaceous]] plants with annual, biennial or perennial lifespans.
 
−
 
 
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The '''[[leaf|leaves]]''' are [[phyllotaxis|alternate]] (rarely [[phyllotaxis|opposite]]), sometimes organized in basal [[rosette]]s. They are very often pinnately incised and do not have [[stipule]]s.
 
−
 
 
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The structure of the '''[[flower]]s''' is extremely uniform throughout the family. They have four free saccate sepals and four clawed free [[petals]], staggered. They can be [[Floral symmetry|disymmetric]] or slightly [[Floral symmetry|zygomorphic]], with a typical cross-like arrangement (hence the name 'Cruciferae'). They have six [[stamen]]s, four of which are longer (as long as the petals, so relatively short in fact) and are arranged in a cross like the petals and the other two are shorter ('''tetradynamous''' flower). The [[pistil]] is made up of two fused [[carpel]]s and the style is very short, with two lobes. Superior ovary. The flowers form ebracteate [[Inflorescence#simple_inflorescences|racemose]] inflorescences, often apically corymb-like.
 
−
 
 
−
[[Pollination]] occours by [[entomogamy]], nectar is produced at the base of the stamens and stored on the sepals.
 
  
−
[[Image:Cardamine.impatiens.pods.jpg|thumb|Siliquae of ''[[Cardamine impatiens]]'']]
+
The family contains species of great economic importance, providing much of the world's winter vegetable supply. In addition to watercress, members of the Brassicaceae family include [[cabbage]], [[broccoli]], [[cauliflower]], [[brussels sprout]]s, [[collard]]s, and [[kale]] (all cultivars of one species, ''[[Brassica oleracea]]''), [[Chinese kale]], [[rutabaga]] (also known as Swedish turnips or swedes), [[seakale]], [[Brassica rapa|turnip]], [[radish]], and [[Kohl Rabi|kohl rabi]]. Other well known members of the Brassicaceae include [[rapeseed]] ([[canola]] and others), [[mustard plant|mustard]], [[horseradish]], and [[wasabi]].  
−
The '''[[fruit]]''' is a peculiar kind of [[capsule (fruit)|capsule]] named '''siliqua''' (plural siliquae, American English silique/siliques). It opens by two valves, which are the modified carpels, leaving the [[seed]]s attached to a framework made up of the placenta and tissue from the junction between the valves ('''replum'''). There is often an indehiscent beak at the top of the style and one or more [[seeds]] may be borne there. Where a siliqua is less than three times as long as it is broad , it is usually termed a '''silicula'''. The siliqua may  break apart at constrictions occurring between the segments of the seeds, thus forming a sort of [[loment]] (e.g. ''[[Raphanus]]''), it may eject the seeds explosively (e.g. ''[[Cardamine]]'') or may be evolved in a sort of [[samara]] (e.g. ''[[Isatis]]''). Unsurprisingly the fruit is often the most important diagnostic character for plants in this family.  
 
  
−
The Brassicaceae do not form [[mycorrhizae]], although rare exceptions do exist.
+
Brassicaceae consists only of [[herbaceous]] plants with annual, biennial, or perennial lifespans. The '''[[leaf|leaves]]''' are [[phyllotaxis|alternate]] (rarely opposite), sometimes organized in basal [[rosette]]s. They are very often pinnately incised and do not have [[stipule]]s.
  
−
Most members share a suite of glucosinolate compounds that has a typical pungent odour usually associated with cole crops.
+
The structure of the '''[[flower]]s''' is extremely uniform throughout the family. They have four free [[saccate]] sepals and four clawed free [[petals]], staggered. They can be [[Floral symmetry|disymmetric]] or slightly [[zygomorphic]], with a typical cross-like arrangement. They have six [[stamen]]s, four of which are longer (as long as the petals, so relatively short in fact) and are arranged in a cross like the petals and the other two are shorter (''tetradynamous'' flower). The [[pistil]] is made up of two fused [[carpel]]s and the [[style]] is very short, with two lobes (Superior ovary). The flowers form [[ebracteate]] [[Inflorescence#simple_inflorescences|racemose]] inflorescences, often apically [[corymb]]-like.
  
 +
[[Pollination]] occurs by [[entomogamy]]; Nectar is produced at the base of the stamens and stored on the sepals.
  
−
''N. microphyllum''; formerly ''Rorippa nasturtium-aquaticum'', ''R. microphylla'') are fast-growing, aquatic or semi-aquatic, [[perennial plant]]s native from [[Europe]] to central [[Asia]],
+
Brassicaceae [[fruit]] is a peculiar kind of [[capsule (fruit)|capsule]] named siliqua (plural siliquae, American English silique/siliques). It opens by two valves, which are the modified carpels, leaving the [[seed]]s attached to a framework made up of the placenta and tissue from the junction between the valves (replum). There is often an indehiscent beak at the top of the style and one or more [[seeds]] may be borne there. Where a siliqua is less than three times as long as it is broad, it is usually termed a silicula. The siliqua may break apart at constrictions occurring between the segments of the seeds, thus forming a sort of [[loment]] (for example, ''[[Raphanus]]''); it may eject the seeds explosively (for example, ''[[Cardamine]]''); or may be evolved in a sort of [[samara]] (for example, ''[[Isatis]]''). Unsurprisingly the fruit is often the most important diagnostic character for plants in this family.
  
−
The hollow stems of watercress are floating and the leaves are pinnately compound. Watercresses produce small white and green [[flower]]s in clusters.
+
'''''Nasturtium officinale''''' and '''''N. microphyllum''''' are fast-growing [[perennial plant]]s native from [[Europe]] to central [[Asia]]. The hollow stems of watercress are floating and the leaves are pinnately compound. Watercresses produce small white and green [[flower]]s in clusters.
 
   
 
   
−
''Nasturtium nasturtium-aquaticum'' (nomenclaturally invalid) and ''Sisymbrium nasturtium-aquaticum'' L. are synonyms of ''N. officinale''.  
+
''Nasturtium nasturtium-aquaticum'' (nomenclaturally invalid) and ''Sisymbrium nasturtium-aquaticum'' L. are synonyms of ''N. officinale''. ''Nasturtium officinale'' var ''microphyllum'' (Boenn. ex Reich.) Thellung is a synonym of ''N. microphyllum'' (ITIS, 2004). These species are also listed in some sources as belonging to the genus, ''[[Rorippa]]'', although molecular evidence shows that the aquatic species with hollow stems are more closely related to ''Cardamine'' than ''Rorippa'' (Al-Shehbaz and Price, 1998). Watercresses are not related to the flowers in the genus, ''[[Tropaeolum]]'' (family [[Tropaeolaceae]]), popularly known as "[[Nasturtium (popular name)|nasturtiums]]."
−
''Nasturtium officinale'' var ''microphyllum'' (Boenn. ex Reich.) Thellung is a synonym of ''N. microphyllum'' (ITIS, 2004). These species are also listed in some sources as belonging to the genus, ''[[Rorippa]]'', although molecular evidence shows that the aquatic species with hollow stems are more closely related to ''Cardamine'' than ''Rorippa'' (Al-Shehbaz & Price, 1998). Watercresses are not related to the flowers in the genus, ''[[Tropaeolum]]'' (Family [[Tropaeolaceae]]), popularly known as "[[Nasturtium (popular name)|nasturtiums]]".
 
  
 
==Watercress cultivation==
 
==Watercress cultivation==
−
[[Image:WarnfordWatercress.jpg|thumb|Watercress beds in [[Warnford]], [[Hampshire]]]]
+
[[Image:WarnfordWatercress.jpg|thumb|240px|Watercress beds in [[Warnford]], [[Hampshire]], United Kingdom]]
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Cultivation of watercress is practical on both a large scale and a garden scale. Being semi-aquatic, watercress is well-suited to [[hydroponics|hydroponic]] cultivation, thriving best in water that is slightly [[alkaline]]. It is frequently produced around the headwaters of [[chalk stream]]s. In many local markets the demand for hydroponically-grown watercress exceed supplies. This is due in part to the fact that cress [[Leaf|leaves]] are unsuitable for distribution in dried form and can only be stored for a short period.
+
Cultivation of watercress is practical on both a large scale and a garden scale.  
  
−
However (in the [[UK]] at least), the packaging used by supermarkets using sealed plastic bags under some internal pressure (a plastic envelope containing moisture and pressurised (inflated) to prevent crushing of contents) has allowed the distribution of watercress (and sometimes a mixture of it with other salad leaves). This has allowed national availability with a once purchased storage life of 1 - 2 days in chilled/refrigerated storage.  
+
Being semi-aquatic, watercress is well-suited to [[hydroponics|hydroponic]] cultivation, thriving best in [[water]] that is slightly [[alkaline]]. It is frequently produced around the headwaters of [[chalk stream]]s. In many local markets, the demand for hydroponically-grown watercress exceed supplies. This is due in part to the fact that cress [[Leaf|leaves]] are unsuitable for distribution in dried form and can only be stored for a short period.  
  
−
If unharvested, watercress can grow to a height of 50-120 cm. Also sold as [[Sprouting|sprouts]], the edible shoots are harvested days after germination.
+
However (in the [[United Kingdom]] at least), the use by supermarkets of sealed plastic bags under some internal pressure (a plastic envelope containing moisture and pressurized (inflated) to prevent crushing of contents) has allowed the distribution of watercress (and sometimes a mixture of it with other salad leaves). This has allowed national availability with a once purchased storage life of one to two days in chilled/refrigerated storage.  
  
−
Like many plants in this family, the foliage of watercress becomes bitter when the plants begin producing flowers.
+
If unharvested, watercress can grow to a height of 50-120 centimeters. Also sold as [[Sprouting|sprouts]], the edible shoots are harvested days after germination.
  
−
[[Huntsville, Alabama]] now uses the slogan "Rocket City", but before it developed a missile industry it called itself the "Watercress Capital of the World".<ref>[http://www.motherjones.com/news/feature/2001/07/missile.html Huntsville's Missile Payload<!-- Bot generated title —>]</ref>
+
As with many plants in this family, the foliage of watercress becomes bitter when the plants begin producing flowers.
  
−
Watercress is one of the main ingredients in [[V8 (beverage)| V8  Vegetable Juice]]. Watercress is often used in sandwiches, such as those made for [[Tea (meal)|afternoon tea]].
+
==Culinary and medicinal uses==
 +
Watercress is a rich source of [[vitamin C]], a good source of [[vitamin A]], and a source of [[calcium]], [[iron]], and [[folic acid]] (Bender and Bender 2005; LSE 2007).  
  
−
Watercress is grown in a number of counties of the UK, most notably, Hertfordshire, Hampshire, Wiltshire and Dorset, although the first commercial cultivation was along the [[River Ebbsfleet]] in [[Kent]]. Alresford, near Winchester, is often considered the watercress capital of Britain (to the extent that a steam railway line is named after the famous local crop). In recent years, watercress has become more widely available in the UK, at least in the South-East, being stocked pre-packed in some supermarkets, as well as fresh by the bunch at  farmers' markets and greengrocers. Value-added produce such as the traditional watercress soup, as well as watercress pesto are increasingly easy to source.
+
Watercress has a pungent, slightly bitter taste, with a peppery snap (Herbst 2001). It is popular in salads and as a garnish, and may be used in soups, salads, and diverse cooked dishes (Herbst 2001). Watercress is one of the main ingredients in [[V8 (beverage)| V8 Vegetable Juice]].  
  
−
==Health benefits and cancer defense==
+
Many benefits from eating watercress are claimed, such as that it acts as a mild [[stimulant]], a source of [[phytochemical]]s and [[antioxidant]]s, a [[diuretic]], an [[expectorant]], and a [[digestive]] aid. It also appears to have [[cancer]]-suppressing properties (LSE 2007). It is widely believed to help defend against [[lung cancer]] (Hecht et al. 1995; Aisen and Cavender 2005; Bhat 2007).
−
Watercress contains significant amounts of [[iron]], [[calcium]] and [[folic acid]], in addition to vitamins [[vitamin A|A]] and [[vitamin C|C]].<ref name=lse>[http://www.lse.co.uk/ShowStory.asp?story=GE1534106Y&news_headline=watercress_diet_can_cut_the_risk_of_cancer Watercress Diet 'Can Cut The n Risk Of Cancer' - UK News Headlines<!-- Bot generated title —>]</ref> In some regions watercress is regarded as a [[weed]], in other regions as an [[aquatic plant|aquatic]] [[vegetable]] or [[herb]]. Watercress crops grown in the presence of [[animal]] [[waste]] can be a haven for [[parasite]]s such as the [[Liver Fluke|liver fluke]] ''[[Fasciola hepatica]]''.{{Fact|date=February 2007}}
 
  
−
Many benefits from eating watercress are claimed, such as that it acts as a mild [[stimulant]], a source of [[phytochemical]]s and [[antioxidant]]s, a [[diuretic]], an [[expectorant]], and a [[digestive]] aid.{{Fact|date=February 2007}} It also appears to have [[cancer]]-suppressing properties.<ref name=lse>[http://www.lse.co.uk/ShowStory.asp?story=GE1534106Y&news_headline=watercress_diet_can_cut_the_risk_of_lung cancer Watercress Diet 'Can Cut The Risk Of Cancer' - UK News Headlines<!-- Bot generated title —>]</ref> It is widely believed to help defend against [[lung cancer]].<ref>[http://cebp.aacrjournals.org/cgi/content/abstract/4/8/877 Cancer Epidemiology Biomarkers & Prevention] - Effects of watercress consumption on metabolism of a tobacco-specific lung carcinogen in smokers</ref><ref>[http://www.medicalnewstoday.com/articles/30696.php Medical News TODAY] - Compounds in broccoli, cauliflower, and watercress block lung cancer progression</ref><ref>[http://www.timesonline.co.uk/tol/news/uk/health/article1388394.ece Times Online] - Eating raw watercress every day may reduce risk of cancer</ref>
+
In some regions, watercress is regarded as a [[weed]] (USDA 2008), in other regions as an [[aquatic plant|aquatic]] [[vegetable]] or [[herb]]. Watercress crops grown in the presence of [[animal]] [[waste]], such as near a cattle or sheep growing area, can be a haven for [[parasite]]s such as the [[Liver Fluke|liver fluke]] ''[[Fasciola hepatica]],'' which causes [[fasciolosis]].
  
 
==References==
 
==References==
−
{{Reflist}}
+
* Aisen, C.F., and L. Cavender. 2005. [http://www.medicalnewstoday.com/articles/30696.php Compounds in broccoli, cauliflower, and watercress block lung cancer progression.] ''Medical News Today'' September 16, 2005. Retrieved April 12, 2008.
−
* Al-Shehbaz, I. and R. A. Price. 1998. Delimitation of the genus ''Nasturtium'' (Brassicaceae). ''Novon'', 8: 124-126.
+
* Al-Shehbaz, I. and R. A. Price. 1998. Delimitation of the genus ''Nasturtium'' (Brassicaceae). ''Novon'' 8: 124-126.
−
 
+
* Bender, D. A., and A. E. Bender. 2005. ''A Dictionary of Food and Nutrition''. New York: Oxford University Press. ISBN 0198609612.
−
==See also==
+
* Bhat, D. 2007. [http://www.timesonline.co.uk/tol/news/uk/health/article1388394.ece Eating raw watercress every day may reduce risk of cancer.] ''Times Online'' February 17, 2007. Retrieved April 12, 2008.
−
* [http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=22993 Rorippa nasturtium-aquaticum] (ITIS)
+
* Hecht, S. S., F. L. Chung, J. P. Richie, S. A. Akerkar, A. Borukhova, L. Skowronski, and S. G. Carmella. 1995. [http://cebp.aacrjournals.org/cgi/content/abstract/4/8/877 Effects of watercress consumption on metabolism of a tobacco-specific lung carcinogen in smokers.] ''Cancer Epidemiology Biomarkers & Prevention'' 4(8): 877-884.  
−
* [http://www.watercressfestival.org www.watercressfestival.org] - The Alresford Watercress Festival
+
* Herbst, S. T. 2001. ''The New Food Lover's Companion: Comprehensive Definitions of Nearly 6,000 Food, Drink, and Culinary Terms. Barron's Cooking Guide.'' Hauppauge, NY: Barron's Educational Series. ISBN 0764112589.
−
* [http://www.watercress.co.uk www.watercress.co.uk]
+
* Life Style Extra (LSE). 2007. [http://www.lse.co.uk/ShowStory.asp?story=GE1534106Y&news_headline=watercress_diet_can_cut_the_risk_of_cancer Watercress diet "can cut the risk of cancer."] ''LifeStyleExtra.com'' February 15, 2007. Retrieved April 12, 2008.
−
* [http://www.watercress.com www.watercress.com]
+
* Plants for a Future (PFAF). 2000. [http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Nasturtium+microphyllum ''Nasturium microphyllum.''] ''Plants for a Future''. Retrieved April 12, 2008.
−
* [http://www.watercressline.co.uk www.watercressline.co.uk] - The [[Watercress Line]]/[[Mid-Hants Railway]]
+
* United States Department of Agriculture (USDA), Natural Resources Conservation Service. 2008. [http://plants.usda.gov/java/profile?symbol=NAMI2 Plants profile: ''Nasturtium microphyllum.''] ''United States Department of Agriculture''. Retrieved April 12, 2008.
−
*[http://www.chalkevalleywatercress.co.uk Chalke Valley Watercress]
 
−
* [http://www.alresford.org Alresford's Chamber of Commerce site]
 
  
 
[[Category:Life sciences]]
 
[[Category:Life sciences]]

Latest revision as of 17:54, 20 August 2008

Watercress
Nasturtium microphyllum, a watercress
Nasturtium microphyllum, a watercress
Scientific classification
Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Order: Brassicales
Family: Brassicaceae
Genus: Nasturtium R. Br.
Species

Nasturtium officinale W.T. Aiton Nasturtium microphyllum Boenn. ex Rchb.

Watercress is the common name for a fast-growing, aquatic or semi-aquatic, herbaceous, perennial plant, Nasturtium officinale (formerly Rorippa nasturtium-aquaticum) of the mustard family Brassicaceae, characterized by hollow stems, pinnately compound leaves, and small flowers. The term also is used for a similar and closely related plant, Nasturtium microphyllum (formerly Rorippa microphylla), which is sometimes listed as Nasturtium officinale var. microphyllum and commonly known as onerow yellowcress (USDA 2008; PFAF 2000). N. officinale is sometimes referred to as "green watercress," with N. microphyllum referenced as brown or winter watercress (Bender and Bender 2005).

Watercress is among the oldest known leaf vegetables consumed by human beings. These two species are botanically related to garden cress and mustard—all noteworthy for a peppery, tangy flavor. Added to salads, soups, or sandwiches, or used as a garnish, watercress provides a nutritious addition to food, while its pungent, peppery flavor adds to the culinary experience.

Description

The two species of watercress belong to the flowering plant family Brassicaceae (or Cruciferae), also known as the crucifers, the mustard family, or the cabbage family. (Cruciferae is an older name for the family. It means "cross-bearing," because the four petals of their flowers are reminiscent of a cross.)

The family contains species of great economic importance, providing much of the world's winter vegetable supply. In addition to watercress, members of the Brassicaceae family include cabbage, broccoli, cauliflower, brussels sprouts, collards, and kale (all cultivars of one species, Brassica oleracea), Chinese kale, rutabaga (also known as Swedish turnips or swedes), seakale, turnip, radish, and kohl rabi. Other well known members of the Brassicaceae include rapeseed (canola and others), mustard, horseradish, and wasabi.

Brassicaceae consists only of herbaceous plants with annual, biennial, or perennial lifespans. The leaves are alternate (rarely opposite), sometimes organized in basal rosettes. They are very often pinnately incised and do not have stipules.

The structure of the flowers is extremely uniform throughout the family. They have four free saccate sepals and four clawed free petals, staggered. They can be disymmetric or slightly zygomorphic, with a typical cross-like arrangement. They have six stamens, four of which are longer (as long as the petals, so relatively short in fact) and are arranged in a cross like the petals and the other two are shorter (tetradynamous flower). The pistil is made up of two fused carpels and the style is very short, with two lobes (Superior ovary). The flowers form ebracteate racemose inflorescences, often apically corymb-like.

Pollination occurs by entomogamy; Nectar is produced at the base of the stamens and stored on the sepals.

Brassicaceae fruit is a peculiar kind of capsule named siliqua (plural siliquae, American English silique/siliques). It opens by two valves, which are the modified carpels, leaving the seeds attached to a framework made up of the placenta and tissue from the junction between the valves (replum). There is often an indehiscent beak at the top of the style and one or more seeds may be borne there. Where a siliqua is less than three times as long as it is broad, it is usually termed a silicula. The siliqua may break apart at constrictions occurring between the segments of the seeds, thus forming a sort of loment (for example, Raphanus); it may eject the seeds explosively (for example, Cardamine); or may be evolved in a sort of samara (for example, Isatis). Unsurprisingly the fruit is often the most important diagnostic character for plants in this family.

Nasturtium officinale and N. microphyllum are fast-growing perennial plants native from Europe to central Asia. The hollow stems of watercress are floating and the leaves are pinnately compound. Watercresses produce small white and green flowers in clusters.

Nasturtium nasturtium-aquaticum (nomenclaturally invalid) and Sisymbrium nasturtium-aquaticum L. are synonyms of N. officinale. Nasturtium officinale var microphyllum (Boenn. ex Reich.) Thellung is a synonym of N. microphyllum (ITIS, 2004). These species are also listed in some sources as belonging to the genus, Rorippa, although molecular evidence shows that the aquatic species with hollow stems are more closely related to Cardamine than Rorippa (Al-Shehbaz and Price, 1998). Watercresses are not related to the flowers in the genus, Tropaeolum (family Tropaeolaceae), popularly known as "nasturtiums."

Watercress cultivation

Watercress beds in Warnford, Hampshire, United Kingdom

Cultivation of watercress is practical on both a large scale and a garden scale.

Being semi-aquatic, watercress is well-suited to hydroponic cultivation, thriving best in water that is slightly alkaline. It is frequently produced around the headwaters of chalk streams. In many local markets, the demand for hydroponically-grown watercress exceed supplies. This is due in part to the fact that cress leaves are unsuitable for distribution in dried form and can only be stored for a short period.

However (in the United Kingdom at least), the use by supermarkets of sealed plastic bags under some internal pressure (a plastic envelope containing moisture and pressurized (inflated) to prevent crushing of contents) has allowed the distribution of watercress (and sometimes a mixture of it with other salad leaves). This has allowed national availability with a once purchased storage life of one to two days in chilled/refrigerated storage.

If unharvested, watercress can grow to a height of 50-120 centimeters. Also sold as sprouts, the edible shoots are harvested days after germination.

As with many plants in this family, the foliage of watercress becomes bitter when the plants begin producing flowers.

Culinary and medicinal uses

Watercress is a rich source of vitamin C, a good source of vitamin A, and a source of calcium, iron, and folic acid (Bender and Bender 2005; LSE 2007).

Watercress has a pungent, slightly bitter taste, with a peppery snap (Herbst 2001). It is popular in salads and as a garnish, and may be used in soups, salads, and diverse cooked dishes (Herbst 2001). Watercress is one of the main ingredients in V8 Vegetable Juice.

Many benefits from eating watercress are claimed, such as that it acts as a mild stimulant, a source of phytochemicals and antioxidants, a diuretic, an expectorant, and a digestive aid. It also appears to have cancer-suppressing properties (LSE 2007). It is widely believed to help defend against lung cancer (Hecht et al. 1995; Aisen and Cavender 2005; Bhat 2007).

In some regions, watercress is regarded as a weed (USDA 2008), in other regions as an aquatic vegetable or herb. Watercress crops grown in the presence of animal waste, such as near a cattle or sheep growing area, can be a haven for parasites such as the liver fluke Fasciola hepatica, which causes fasciolosis.

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