This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Climbing, trailing, or diffuse annual or perennial herbs, often tuberous-rooted. Leaves alternate, peltate, or palmately-lobed or dissected; stipules none, or minute. Flowers pedunculate, solitary, axillary, irregular, orange-yellow, purple, or blue. Sepals 5, the upper one produced downwards into a free spur. Petals unequal, 5, or by abortion fewer, often fringed or bearded at the base. Stamens 8, free, all antheriferous. Fruit of usually three fleshy indehiscent 1-seeded carpels; seeds exalbuminous. About thirty-five species are known, all inhabiting South America. The name is said to be derived from a trophy. The tubers of some species are used as an article of diet in Peru.
1. T. aduncum, syn. T. peregrinum. - This is commonly known as the Canary Creeper, and sometimes named T. Canariense; but it is a native of America only. It is very distinct, and readily distinguished by its slender stems, 3- to 5-lobed leaves, and bright canary-yellow flowers with narrow petals.
2. T. majus (fig. 60). Taller Nasturtium or Indian Cress. - This is the common tall-growing kind, the carpels of which are used as a substitute for capers. In the typical plant the flowers are yellow, but there are crimson, scarlet, orange, and striped single varieties, and also double-flowered forms, in cultivation. 3. T. minus. Smaller Nasturtium. - Similar to the last, of dwarfer growth, with smaller flowers of a more reddish-orange colour. The varieties of this are very numerous and beautiful. The carpels of this are said to be superior for pickling to those of the preceding species.
Fig. 60. Tropaeolum majus. (1/4 nat. size.)
4. T. Lobbianum. - A strong growing species, more like No. 2 in habit, but the leaves are slightly villous, and the orange and scarlet petals are fringed. Many of the beautiful bedding varieties belong to this species, though it is probable that some of them are of hybrid origin between this and the foregoing.
Perennial tuberous-rooted Species.
5. T. edule. - A climbing species with slender tortuous stems and leaves of 5 to 7 narrow lanceolate glaucous divergent lobes. Flowers orange or yellow. This and all of the perennial species are rather tender, and comparatively rare in gardens on account of the difficulty experienced in growing them.
6. T. tuberosum. - A smaller plant than the last. Leaves smooth, obtusely 5-lobed; lobes rounded. Petals yellow within, spur reddish-orange.
7. T. pentaphyllum, syn. Chymocdrpus pentaphyllus. - A very distinct species with slender tortuous stems. Leaves composed of five distinct oblong-lanceolate leaflets. In this species the calyx, especially the bright red spur, forms the most conspicuous part of the flowers, the petals being small, greenish in colour, and only two in number. The fruit of this, too, is more decidedly fleshy and juicy.