This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
A large genus of beautiful-flowering herbaceous plants having either bulbs or rhizomes. For market purposes the German (I, germanica) and Florentine (I. florentina) are the best. They grow in any soil and are easily accommodated in out-of-the-way borders, or between rows of standard and half-standard fruit trees. They are chiefly valuable for the large splendid purple and pale-lilac or white flowers which are produced in great profusion in May, and generally sell well, although the individual flowers do not last a long time. With the German and Florentine Irises market growers would do well to associate other "bearded" and gaily coloured kinds as follows: aphylla, with frilled flowers having bright colours on a white ground; amoena, with white standards, and falls of various shades; neglecta, with standards varying from lavender to purple; pallida, with flowers mostly of lavender, blue, or rosy shades; squalens, shades of copper, bronze, and pale brown; variegata, standards yellow with claret-brown falls. In each of these sections there are numerous varieties (some with fancy names), and they may be all regarded as valuable market plants - chiefly for cut flowers, but also for the "roots".
Fig. 211. - Iris laevigata (Koempferi).
The next most important commercial Iris is the Spanish one (7. Xiphion), a beautiful bulbous species in which a fine trade is done in the bulbs amongst amateurs, market, private, and public gardeners in the autumn. Hundreds of thousands of bulbs are imported from Holland. Market growers usually purchase to obtain cut flowers in early summer before the open-air blossoms appear in May and June. The bulbs are placed in shallow boxes or 2 or 3 in. apart in large pots in good rich soil, and buried an inch or two below the surface. Root action is established out-of-doors or in cold frames, and the pots or boxes are brought into the greenhouses from Christmas onwards as required. Forcing is very gentle, 60° to 65° F. being sufficient, and better than a higher temperature. When grown in pots, the plants, flowers, and all may be sold as they stand, if worth while. The chief trade, however, is in the cut flowers, and if these reach market at a favourable time good prices are realized. Even in May and June, prices for blooms of Spanish Irises are by no means to be despised, although much lower than for those of earlier indoor crops. Outdoor plants flourish in any good and well-drained garden soil in a warm sunny position. Perhaps the foot of a south wall where Peaches, Nectarines, or other fruit trees are grown is one of the best positions for them; and although the bulbs gradually die out, a crop may be secured for several seasons after the first planting in early autumn.
Fig. 212. - Iris Susiana.
Another class of business is done in Spanish Iris. Unopened spikes of bloom from Southern France, etc, find their way to Covent Garden and other British markets, and are purchased by market growers, who take them home and open them in the warmth of a green-house, the stems of course being placed in jars of water. In a day or two the blossoms open, and are then taken back and resold to florists and others, leaving the enterprising mar-ketman and the foreigner both more or less satisfied. There are many beautiful kinds of Spanish Irises with fancy names, the colours varying from fine white to white with orange or yellow blotches, and pure yellows, pure blues light and dark, lavender, bronze, etc, many being beautifully fumed or smoked. Some varieties cost much more than others, but good results are obtained from fine mixtures.
Another Iris in which some trade is done is the variegated form of the Common British Flag (1. pseudacorus). The leaves in spring are beautifully variegated with green and gold, and in this state roots sell well for a time owing to the ornamental appearance. During the summer and autumn, however, the variegation gradually disappears, but reappears the following spring with the new leaves. Moist and half-shady spots should be chosen to grow this variegated plant well; also the variegated form of the Gladwin or Roast Beef Plant (1. foetidissima).
While the Irises mentioned above constitute the bulk of the market grower's stock in trade, many more species are dealt in by hardy plant growers, but of course in comparatively small quantities. The trade, however, is increasing of late years, as owners of gardens are beginning to recognize the decorative value of the numerous species of Iris, and the ease with which most of them may be grown. These Irises may be divided into bulbous and rhizomatous groups, the latter including the Japanese Iris, I. loevigata or Koempferi (tig. 211), and also the gorgeous-flowered "Cushion" or "Oncocyclus" Irises. The reader will find full botanical and cultural details of these charming Irises either in the Practical Guide to Garden Plants or in The Bulb Booh (J. Weathers). Special attention, however, may be called to Iris Susiana (fig. 212), a magnificent species rather difficult to grow; and to the English Irises (fig. 213), which are similar to the Spanish Irises, and might very well become more popular for cutting purposes amongst market growers.
Fig. 213. - English Irises (Iris xiphioides).