GLADIOLUS, a genus of monocotyledonous plants, belonging to the natural order Iridaceae. They are herbaceous plants growing from a solid fibrous-coated bulb (or corm), with long narrow plaited leaves and a terminal one-sided spike of generally bright-coloured irregular flowers. The segments of the limb of the perianth are very unequal, the perianth tube is curved, funnel-shaped and widening upwards, the segments equalling or exceeding the tube in length. There are about 150 known species, a large number of which are South African, but the genus extends into tropical Africa, forming a characteristic feature of the mountain vegetation, and as far north as central Europe and western Asia. One species G. illyricus (sometimes regarded as a variety of G. communis) is found wild in England, in the New Forest and the Isle of Wight. Some of the species have been cultivated for a long period in English flower-gardens, where both the introduced species and the modern varieties bred from them are very ornamental and popular. G. segetum has been cultivated since 1596, and G. byzantinus since 1629, while many additional species were introduced during the latter half of the 18th century. One of the earlier of the hybrids originated in gardens was the beautiful G. Colvillei, raised in the nursery of Mr Colville of Chelsea in 1823 from G. tristis fertilized by G. cardinalis. In the first decade of the 19th century, however, the Hon. and Rev. W. Herbert had successfully crossed the showy G. cardinalis with the smaller but more free-flowering G. blandus, and the result was the production of a race of great beauty and fertility. Other crosses were made with G. tristis, G. oppositiflorus, G. hirsutus, G. alatus and G. psittacinus; but it was not till after the production of G. gandavensis that the gladiolus really became a general favourite in gardens. This fine hybrid was raised in 1837 by M. Bedinghaus, gardener to the duc d’Aremberg, at Enghien, crossing G. psittacinus and G. cardinalis. There can, however, be little doubt that before the gandavensis type had become fairly fixed the services of other species were brought into force, and the most likely of these were G. oppositiflorus (which shows in the white forms), G. blandus and G. ramosus. Other species may also have been used, but in any case the gandavensis gladiolus, as we now know it, is the result of much crossing and inter-crossing between the best forms as they developed (J. Weathers, Practical Guide to Garden Plants). Since that time innumerable varieties have appeared only to sink into oblivion upon being replaced by still finer productions.
The modern varieties of gladioli have almost completely driven the natural species out of gardens, except in botanical collections. The most gorgeous groups—in addition to the gandavensis type—are those known under the names of Lemoinei, Childsi, nanceianus and brenchleyensis. The last-named was raised by a Mr Hooker at Brenchley in 1848, and although quite distinct in appearance from gandavensis, it undoubtedly had that variety as one of its parents. Owing to the brilliant scarlet colour of the flowers, this is always a great favourite for planting in beds. The Lemoinei forms originated at Nancy, in France, by fertilizing G. purpureo-auratus with pollen from G. gandavensis, the first flower appearing in 1877, and the plants being put into commerce in 1880. The Childsi gladioli first appeared in 1882, having been raised at Baden-Baden by Herr Max Leichtlin from the best forms of G. gandavensis and G. Saundersi. The flowers of the best varieties are of great size and substance, often measuring 7 to 9 in. across, while the range of colour is marvellous, with shades of grey, purple, scarlet, salmon, crimson, rose, white, pink, yellow, &c., often beautifully mottled and blotched in the throat. The plants are vigorous in growth, often reaching a height of 4 to 5 ft. G. nanceianus was raised at Nancy by MM. Lemoine and were first put into commerce in 1889. Next to the Childsi group they are the most beautiful, and have the blood of the best forms of G. Saundersi and G. Lemoinei in their veins. The plants are quite as hardy as the gandavensis hybrids, and the colours of the flowers are almost as brilliant and varied in hue as those of the Childsi section.
A deep and rather stiff sandy loam is the best soil for the gladiolus, and this should be trenched up in October and enriched with well-decomposed manure, consisting partly of cow dung, the manure being disposed altogether below the corms, a layer at the bottom of the upper trench, say 9 in. from the surface, and another layer at double that depth. The corms should be planted in succession at intervals of two or three weeks through the months of March, April and May; about 3 to 5 in. deep and at least 1 ft. apart, a little pure soil or sand being laid over each before the earth is closed in about them, an arrangement which may be advantageously followed with bulbous plants generally. In hot summer weather they should have a good mulching of well-decayed manure, and, as soon as the flower spikes are produced, liquid manure may occasionally be given them with advantage.
The gladiolus is easily raised from seeds, which should be sown in March or April in pots of rich soil placed in slight heat, the pots being kept near the glass after they begin to grow, and the plants being gradually hardened to permit their being placed out-of-doors in a sheltered spot for the summer. Modern growers often grow the seeds in the open in April on a nicely prepared bed in drills about 6 in. apart and 1 in. deep, covering them with finely sifted gritty mould. The seed bed is then pressed down evenly and firmly, watered occasionally and kept free from weeds during the summer. In October they will have ripened off, and must be taken out of the soil, and stored in paper bags in a dry room secure from frost. They will have made little bulbs from the size of a hazel nut downwards, according to their vigour. In the spring they should be planted like the old bulbs, and the larger ones will flower during the season, while the smaller ones must be again harvested and planted out as before. The time occupied from the sowing of the seed until the plant attains its full strength is from three to four years. The approved sorts, which are identified by name, are multiplied by means of bulblets or offsets or “spawn,” which form around the principal bulb or corm; but in this they vary greatly, some kinds furnishing abundant increase and soon becoming plentiful, while others persistently refuse to yield offsets. The stately habit and rich glowing colours of the modern gladioli render them exceedingly valuable as decorative plants during the late summer months. They are, moreover, very desirable and useful flowers for cutting for the purpose of room decoration, for while the blossoms themselves last fresh for some days if cut either early in the morning or late in the evening, the undeveloped buds open in succession, if the stalks are kept in water, so that a cut spike will go on blooming for some time.