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Tropaeolum
Tropaeolum majus
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Brassicales
Family:	Tropaeolaceae
Genus:	Tropaeolum L.
Species
About 80 species, see text.

Tropaeolum (/trˈpiːələm/), commonly known as Nasturtium (/næˈstɜːrʃəm/; literally "nose-twister" or "nose-tweaker"), is a genus of roughly 80 species of annual and perennial herbaceous flowering plants and the only genus in the family Tropaeolaceae. It should not be confused with the Watercresses of the genus Nasturtium, of the Mustard family. The genus Tropaeolum, native to South and Central America, includes several very popular garden plants, the most commonly grown being T. majus, T. peregrinum and T. speciosum. The hardiest species is T. polyphyllum from Chile, the perennial roots of which can survive underground when air temperatures drop as low as -15°C (5°F).

They have showy, often intensely bright flowers, and rounded, peltate (shield-shaped) leaves with the petiole in the centre. The flowers have five petals (sometimes more), a three-carpelled ovary, and a funnel-shaped nectar tube in the back.

Tropaeolum species are used as food plants by the larvae of some Lepidoptera species including Dot Moth and Garden Carpet. A very common "pest" found on Nasturtium in particular is the caterpillar of the Large White (Cabbage White) Butterfly.

The nasturtiums receive their name from the fact that they produce an oil that is similar to that produced by Watercress (Nasturtium officinale), from the family Brassicaceae.

History

The first nasturtium species to be introduced into Europe was named Tropaeolum minus by the Swedish botanist Carl Linnaeus. He chose the genus name because the plant reminded him of an ancient custom. After victory in battle, the Romans used to set up a trophy pole called a "tropaeum". (Latin: Tropaeum from Greek: Tropaion, source of English: "trophy"). On this the armour and weapons of the vanquished foe were hung. Linnaeus was reminded of this by the plant as the round leaves resembled shields and the flowers, blood-stained helmets.

Nasturtiums were also known as "Indian cress". This was because, when they were introduced they were used as a salad ingredient and they originated from South America which at that time was known as the Indies. The 16th century herbalist John Gerard, in his book "Of the Historie of Plants", called the plant "lark's heel". He wrote: "unto the backe part(of the flower) doth hange a taile or spurre, such as hath the larkes heele, called in Latine Consolida regalis."

Description

Tropaeolum is a genus of dicotyledonous annual or perennial plants, often with somewhat succulent stems and sometimes tuberous roots. The alternate leaves are smooth and entire or palmately lobed. The leaf stalks are long and in many species are able to twine round other stems to provide support. The flowers are bisexual and showy, set singly on long stalks in the axils of the leaves. They have five sepals which form a spur below, five irregular petals, eight stamens and a superior ovary.

Cultivation and uses

In cultivation, most varieties of nasturtiums prefer to be grown in direct or indirect sunlight, with a few preferring partial shade.

The most common use of the nasturtium plant in cultivation is as an ornamental flower. It grows easily and prolifically, and is a self-seeding annual.

All parts of the plant are edible. The flower has most often been consumed, making for an especially ornamental salad ingredient; it has a slightly peppery taste reminiscent of watercress, and is also used in stir fry. The unripe seed pods can be harvested and pickled with hot vinegar, to produce a condiment and garnish, sometimes used in place of capers, although the taste is strongly peppery. The mashua (T. tuberosum) produces an edible underground tuber that is a major food source in parts of the Andes.

Companion plants

Nasturtiums are also considered widely useful companion plants. They repel a great many cucurbit pests, like squash bugs, cucumber beetles, and several caterpillars. They have a similar range of benefits for brassica plants, especially broccoli and cauliflower. They also serve as a trap crop against black fly aphids. They also attract beneficial predatory insects.

Taxonomy

Tropaeolum was previously placed in the family Tropaeolaceae along with two other genera, Magallan and Tropaeastrum. Magallan (1 species) was characterised by having winged fruit and Tropaeastrum (2 species) by having no spur while Tropaeolum (86 species) was only diagnosed by the absence of the characteristics of the other two genera. A molecular study undertaken in 2000 found Tropaeolum to be paraphyletic when the other two genera are segregated so Magallan and Tropaeastrum were reduced to synonyms of Tropaeolum. Tropaeolaceae was thus rendered monogeneric.

Species

References

1. Sunset Western Garden Book, 1995:606–607; "Tropaeolum". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
2. "nasturtium". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
3. ^ Perry, Frances (1972). Flowers of the World. The Hamlyn Publishing Group Ltd. pp. 298–300. ISBN 060001634x. {{cite book}}: Check |isbn= value: invalid character (help); Cite has empty unknown parameter: |coauthors= (help)
4. Allaby, Michael (ed.) (1992). The Concise Oxford Dictionary of Botany. Oxford: Oxford University Press. p. 418. ISBN 0198661630. {{cite book}}: |first= has generic name (help); Cite has empty unknown parameter: |coauthors= (help)
5. Andersson, Lennart and Andersson, Stephan (2000). "A molecular phylogeny of Tropaeolaceae and its systematic implications". Taxon. 49 (4). Taxon, Vol. 49, No. 4: 721–736. doi:10.2307/1223973. JSTOR 1223973.{{cite journal}}: CS1 maint: multiple names: authors list (link)

External links

• Tropaeolum by J. S. McFarlane
• Chilean Tropaeolum, by Chileflora
• Poor Man's Capers: How to make gourmet capers from nasturtium seed pods

• Ill-formatted IPAc-en transclusions
• Flowers
• Tropaeolum
• Medicinal plants