Nasturtium is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of five plant species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in the family Brassicaceae

Brassicaceae

Brassicaceae, a medium sized and economically important family of flowering plants , are informally known as the mustards, mustard flowers, the crucifers or the cabbage family....

 (cabbage family), best known for the edible watercress

Watercress

Watercresses are fast-growing, aquatic or semi-aquatic, perennial plants native from Europe to central Asia, and one of the oldest known leaf vegetables consumed by human beings...

es Nasturtium microphyllum (Rorippa microphylla) and Nasturtium officinale (R. nasturtium-aquaticum). Nasturtium was previously synonymised with Rorippa

Rorippa

Rorippa is a flowering plant genus in the cabbage family , containing approximately 80 species native to Europe through central Asia, Africa, and North America. Rorippa species are annual to perennial herbs, usually with yellow flowers and a peppery flavour.Rorippa formerly included several species...

, but molecular evidence supports its maintenance as a distinct genus more closely related to Cardamine

Cardamine

Cardamine , is a large genus in the family Brassicaceae. It contains more than 150 species of annuals and perennials. The genus grows worldwide in diverse habitats, except in the Antarctic. Genus Dentaria is a synonym for Cardamine.The leaves can have different forms, going from minute to...

than to Rorippa sensu stricto (Al-Shehbaz & Price, 1998; Al-Shehbaz, Beilstein & Kellogg, 2006).

These plants are related to garden cress

Garden cress

Garden cress is a fast-growing, edible herb that is botanically related to watercress and mustard, sharing their peppery, tangy flavor and aroma...

 and mustard

Mustard plant

Mustards are several plant species in the genera Brassica and Sinapis whose small mustard seeds are used as a spice and, by grinding and mixing them with water, vinegar or other liquids, are turned into the condiment known as mustard or prepared mustard...

, noteworthy for a peppery, tangy (pungent) flavor. The name Nasturtium comes from the Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 nasus tortus, meaning "twisted nose", in reference to the effect on the nasal passages of eating the plants.
Nasturtium foliage is used as food by the caterpillar

Caterpillar

Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...

s of certain Lepidoptera

Lepidoptera

Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...

, including Orthonama obstipata (The Gem).

One species, Nasturtium gambelii

Nasturtium gambelii

Nasturtium gambelii is a rare species of flowering plant in the mustard family known by the common names Gambel's yellowcress and Gambel's watercress. It is known from three to four scattered occurrences in California, and it has been reported to exist in central Mexico and Guatemala...

, is a federally listed endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 in the United States.

Nomenclature

The genus Nasturtium should not be confused with the common name Nasturtium, referring to the genus Tropaeolum in the Tropaeolaceae family, which includes the popular garden annual

Annual plant

An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...

 of that name (Tropaeolum majus

Tropaeolum majus

Tropaeolum majus is a flowering plant in the family Tropaeolaceae, originating in South America in the Andes from Bolivia north to Colombia. It is of cultivated, probably hybrid origin, with possible parent species including T. minus, T. moritzianum, T. peltophorum, and T...

). Though not related, the leaves of the garden Nasturtium also have a peppery taste.

Species list

One database names 316 species.

• Nasturtium africanum Syn. Nasturtium mesatlanticum O.E. Schulz
• Nasturtium floridanum Florida yellowcress
• Nasturtium gambelii Gambel's yellowcress, or Gambel's watercress
• Nasturtium microphyllum Water cress, Onerow yellowcress
• Nasturtium officinale Water cress

Sources

• Al-Shehbaz, I. A. and R. A. Price, 1998. Delimitation of the genus Nasturtium (Brassicaceae). Novon 8: 124-126.
• Al-Shehbaz, I. A., M. A. Beilstein, and E. A. Kellogg, 2006. Systematics and phylogeny of the Brassicaceae (Cruciferae): an overview. Plant Systematics and Evolution 259: 89–120
• USDA Plant Database for Nasturtium officinale