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.
A very extensive and beautiful genus of hardy and half-hardy bulbous plants, a few of which are natives of the South of Europe and Asia Minor, but the great majority are from South Africa.. Plants with corms or bulb-like rhizomes, and erect slender leafy stems. Leaves broad and strongly nerved or narrow. Flowers spiked or racemose, in some species fragrant, displaying almost every shade and tint of colour imaginable, Perianth-tube curved, widening upwards, more or less irregular. Stigmas 3, flattened upwards. Named from the Latin gladius, a sword, in allusion to the resemblance of the leaves.
Among the European species frequently seen in old gardens we may mention G. communis, a pretty quite hardy plant throwing up numerous spikes of rose-purple flowers in July. There are likewise white and flesh-coloured varieties of this species. G. Byzantinus, is a similar plant with larger flowers of a brighter purple. Of the far more magnificent South African species we must limit ourselves to those more generally cultivated, and from which the numerous garden varieties have been raised : - G. cardinalis, about 2 feet high, with red flowers, the inferior petals bearing in the centre a white or rose spot encircled with purple. G. psittacinus, upwards of 3 feet high, distinguished by its long spike of yellow flowers, whose lower petals are spotted with rusty purple; G. ringens, a superb plant with large slate-coloured flowers exhaling an odour of violets, and finely pitted and striped with violet, the lower petals with yellow spots; G. cuspidatus, large creamy-white flowers bearing brown spots on the lower petals. G. un-dulatus, white rayed with purple in the centre; G. laccatus, rose-coloured; G. ramosus, flesh-coloured; and G. floribundus, purple spotted with white. The species mostly employed in hybridising are G. cardinalis, G. floribundus, and G. psittacinus, and they have given birth to innumerable beautiful varieties either direct from seed or by intercrossing. Among the most notable is the G. Gandavensis (fig. 231), raised in the garden of a celebrated Belgian amateur, the Duke of Arenberg. It is reputed to be the result of a cross between G. cardinalis and G. psitta-clnus. The flowers in this variety are of a bright vermilion shaded with rose, and yellow blotches on the lower petals. The anthers are of a deep violet colour, forming an agreeable contrast with the colours of the perianth. This and G. Brench-leyensis, a beautiful scarlet, may be considered as standard varieties, and they are both extensively employed for planting in large beds.