Tropaeolum Linné (Spec. Pl. [ed. 1] 1: 345, 1753). Type: Tropaeolum majus Linné [lectotype, designated by Nash, North Amer. Fl. 25: 89, 1910]. – Distr: S Mexico, Central America, N, W and SE South America (to Patagonia), esp. along the Andes. Etym: Diminutive of Lat. ‘tropaeum’ (from Gr. ‘tropaion’); mark, token, shield or memorial of victory, trophy; from the shield-like peltate leaves and the flower, which in lateral view resembles a medieval helmet.

  • Incl. Acriviola Miller (1754). Type: Tropaeolum majus Linné.

  • Incl. Cardamindum Adanson (1763). Type: Tropaeolum majus Linné.

  • Incl. Magallana Cavanilles (1798). Type: Magallana porifolia Cavanilles.

  • Incl. Chymocarpus D. Don ex Brewster & al. (1833). Type: Tropaeolum pentaphyllum Lamarck [type according to D. Don, Trans. Linn. Soc. London 17: 14, 1834].

  • Incl. Rixaea Morren (1845). Type: Tropaeolum azureum Bertero ex Colla.

  • Incl. Anisocentra Turczaninow (1863). Type: Anisocentra cardiopetala Turczaninow.

  • Incl. Trophaeastrum Sparre (1991). Type: Tropaeolum patagonicum Spegazzini.

Description as for the family.

The genus Tropaeolum was divided into 10 sections by Sparre & Andersson (1991), but based on the molecular phylogeny of Andersson & Andersson (2000), only 2 well-supported clades can be recognized at sectional level: Section Chilensia embraces 29 taxa with entire petals and often reduced nectar spurs; this section can be further subdivided into 5 subsections (Watson & Flores 2010), and Hershkovitz & al. (2006) found some evidence for hybridization amongst several of its species. Section Tropaeolum (here belongs T. tuberosum) consists of 78 taxa with ciliate petals and well-developed nectar spurs; it can be divided into 6 informal groups.

Economic Importance: The only taxon with more pronounced importance is T. tuberosum, cultivated throughout the Andes as food item (see below for details). A number of Tropaeolum species are cultivated as ornamentals in gardens (esp. T. majus, “Nasturtium”, “Indian Cress”, thought to be the ancient spontaneous hybrid T. minus × T. ferreyrae, originating in Peru and introduced to Europe in 1684 (Mabberley 2017, perhaps subsequently also crossed with T. peltophorum, see Sparre & Andersson 1991). Pickled flower buds of T. majus and some other species are sometimes used as a substitute for capers.

T. tuberosum Ruiz & Pavón (Fl. Peruv. 3: 77, t. 314, 1802). Type: Peru (Ruiz & Pavón s.n. [MA, CONC, F, G, MO]). – Lit: Grau & al. (2003: with ills.); Hind (2010: with ills.). Distr: Colombia, SW Venezuela, Ecuador, Peru, Bolivia, N Peru, N Argentina; high Andes.

≡ Chymocarpus tuberosus (Ruiz & Pavón) Heynhold (1840) ≡ Trophaeum tuberosum (Ruiz & Pavón) Kuntze (1891); incl. Tropaeolum suberosum C. Mueller (1857) (nom. inval., ICN Art. 61.1); incl. Trophaeum denticulatum Kuntze (1891).

T. tuberosum is usually divided into 2 subspecies following Sparre & Andersson (1991), ssp. silvestre for naturally occurring plants, and ssp. tuberosum for the cultivated material. However, Grau & al. (2003: 30) argue that the distinction is questionable since at least some wild accessions from Peru produce elongate tubers. On the other hand, chemical differences between the two subspecies are reported (see references in Grau & al. 2003).

The species is widely cultivated in the high Andes of Ecuador, Peru and Bolivia as a valuable staple food; it is known as “Mashua”, “Añu” or “Isaño”, and a variety of further local names are listed by Grau & al. (2003: 8–9). These authors also provide a detailed synopsis of the biology, agronomy, ethnobotany and genetic variation and breeding perspectives of the crop. The tubers have a water content of 78–94 % and a starch content of 7–10.5% (King 1987; Sperling and King 1990; Grau & al. 2003: 24); dry-matter content can be as low as 8 % (vs. 23 % and more for potatoes) (Condori & al. 2008). In Bolivia, T. tuberosum is mostly grown for feeding to pigs, but it is considered to be under-used for human consumption. To make the tubers palatable to humans, they must be boiled, and they are usually used as components in stews and other dishes (Grau & al. 2003: 23). Under optimal conditions, annual yields of 55–60 t/ha or more can be achieved (Grau & al. 2003: 19; Condori & al. 2008). Tuber formation needs short-day conditions, and starts when day length becomes less than 12 h (Grau & al. 2003: 22). The time from planting to harvest is 6–8 months, and material is propagated only vegetatively, although large quantities of seeds are produced (King 1987). Cultivated clones appear to be self-fertile as seed is also formed in plantings of a single clone (Grau & al. 2003: 13). Apart from its use as food item, T. tuberosum is also valued for medicinal and anti-aphrodisiac qualities in Andean folk medicine (see synopsis by Grau & al. 2003). Many local cultivars exist, partly with different tuber colours, and a Bolivian gene bank holds 80 different accessions (Condori & al. 2008).

T. tuberosum was probably first used medicinally, and only became an important Andean food item much later – the earliest archeological evidence of its usage dates from 650–1350 CE, and the taxon is also shown on Nazca ceramcis dated 1000 CE (Grau & al. 2003: 3, and references there cited).

T. tuberosum ssp. silvestre Sparre (in Harling, G. & Andersson, L. (eds.), Fl. Ecuador 2: 9, 1973). Type: Peru, Lima (Asplund 10847 [S]). – Distr: C Colombia, Ecuador, Bolivia (La Paz), Argentina (Jujuy, Catamarca); woodland, cloud forests, grassland, high-mountain meadows or rocky ground in the high Andes, 2400–3000(–3950) m.

Incl. Tropaeolum buchenavianum Hieronymus (1895); incl. Tropaeolum hieronymi Buchenau (1899) (nom. illeg., ICN Art. 52.1); incl. Tropaeolum septemlobatum Heilborn (1930).

Differs from ssp. tuberosum: Smaller and more slender in all parts; Rstock fusiform, tubers absent (but see discussion above).

T. tuberosum ssp. tuberosum – Distr: SW Venezuela to C Bolivia (Cochabamba, La Paz, Oruro); high Andes, cultivated only. – Figs. 1

Fig. 1
figure 1

Tropaeolum tuberosum ssp. tuberosum. (Copyright: Wikimedia, by Peganum, Henfield, England)

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and 2.

Fig. 2
figure 2

Tropaeolum tuberosum ssp. tuberosum (tuber, longitudinally cut). (Copyright: Wikimedia, Public Domain)

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Incl. Tropaeolum mucronatum Meyen (1835) ≡ Trophaeum mucronatum (Meyen) Kuntze (1891); incl. Tropaeolum cubio Bukasov (1925) (nom. inval., ICN Art. 36.1b).

Herbs with climbing (by twining stems and petioles) to prostrate annual stems to 2–4(–12) m, Rstock with tubers 5–6(–15) × 3–4(–6) cm Ø, yellow or greenish with purple blotches, speckles or streaks; stems, petioles and pedicels often reddish; L alternate, petiole to 10 cm, lamina peltate, 4–5(–6) × 5–6(–7) cm, suborbicular, somewhat (3- to) 5- (to 6-) lobed, often incised to 1/3 of the length of the lamina, basally rounded to subtruncate, tip obtuse to truncate, mucronate; stipules inconspicuous, thin, early caducous; Fl solitary, axillary; Ped 150–200 mm; hypanthium red or reddish, orange or sometimes yellow; Sep 5 (–7 in some clones), upper free Sep lobes 8–10 × 4–5 mm, lanceolate to narrowly triangular, lower lobes 12–14 × 4–5 mm, lanceolate, nectary spur tubular, 18–22 × 5–6 mm Ø at the base; Pet 5 (–7 in some clones), spreading, dark yellow or orange with darker veins, or sometimes pale pink to reddish, the upper shortly clawed, lamina 6–9 × 5–8 mm, suborbicular with entire or repand margins, the lower with a long claw, lamina 10–15 × 4–6 mm, elliptic to subspatulate; Fr dark brown to blackish when fully ripe, mericarps 4–5 mm, rugose, somewhat ribbed, ribs crenulate.