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.
The most generally useful kind for market work is F. re-fracta alba, which has almost pure-white tubular blossoms borne in graceful trusses during the winter season. The cut flowers are largely used by florists, and the prices realized by growers are often remunerative - although the bulbs cost 30s. or more per 1000 at first. Several fine hybrids have been raised of late years, and there are now soft-yellow, orange, and pink varieties obtained from crossing refracta with the pink form known as Armstrongi. The American growers have a fine variety called "Purity", which they grow in hundreds of thousands. It is probably identical with the best forms of alba. The following extract on Freesia culture is taken from The Bulb Book (J. Weathers).
"The bulbs should be obtained as early in August as possible, and the pots in which they are to be placed should be well drained with a layer of crocks over the bottom. Although Freesias will grow in any light rich soil, that which appears to suit them best is a compost of 2 or 3 parts fibrous loam, 1 part leaf soil, and 1 part peat, with a little silver sand or grit. Some growers add a little well-decayed cow-manure, but sometimes the plants are a failure when this is the case. Others use no manure from the cow or horse, and obtain excellent results from loam, peat, leaf soil, and sand. The bulbs should be placed about 1½-3 in. from each other in the pots (three to five bulbs to a 5-in. pot), and should be covered with about 1 in. of compost. This should be pressed down fairly firm with the fingers, and afterwards gently watered to settle it. The bulbs thus potted should be placed in a cold frame on a moist bed of ashes or cinders, or even out-of-doors in a sheltered corner, covered with coconut fibre or fine ashes. When growth has well started and the leaves are 3-4 in. above the soil, a few slender twigs or sticks should be inserted round the rims of the pots to keep the foliage from toppling over. Some judgment is required in watering, care being taken not to give too much on the one hand, or too little on the other. The quantity given will depend largely upon the activity or otherwise of the growth. On the approach of frost, say about the end of September or early October, the plants must be taken from the cold frame in which they were started and transferred to a greenhouse with a temperature of 50° to 60° F. All the bulbs need not be brought in at once, and where a succession of blossom is required in winter and spring, it will be necessary to have batches in several stages of development. As the flowers wither they should be cut off (unless seed is required), and by gradually lessening the supply of water to the roots the leaves begin to fade and the bulbs may be left resting in the pots until the following August or September.