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.
There are, however, potentialities in some Ferns which are entirely latent, and can only be rendered effective artificially. The Hartstongue, of which there are so many beautiful forms, some of which, the Crispums or frilled ones, are perfectly barren, is a case in point. This Fern in time forms a long caudex built up for some inches of persistent bases of the old dead fronds. Lifting such a plant and commencing at the bottom, these bases of a dark colour and sausage-shaped and from ½ - 1 in. long, can be forced off the central core by downward pressure one after another to the number of, it may be, several scores. When the top is nearly reached, the crown may be replanted and will speedily re-establish itself. Each of these bases will be found to be provided with a bundle of roots; these should be snipped off close and the bases then well washed. Not the slightest sign of a bud will be visible, nor normally would one appear, but if these be merely laid upon clean moist silver sand in a glass jar or other transparent receptacle, and kept quite close in a well-lighted place out of bright sunshine, every one will in the course of a few weeks in the growing season, produce first a crop of tiny white pimples or buds, and then a number of rooting plants. One inch-long base taken from a robust specimen bore, in our own experience, no less than thirty-six plants. Other species, such as the Polystichums, are also prone to produce bulbils if the old caudex be damaged, provided all the dead portions be shaved clean off and the remains be treated on the jar system or potted up in very small pots and kept close. One rare variety thus drastically treated broke out into a rash of bulbils which yielded no less than eighty specimens. Experiments in this direction have been mainly effected on British Ferns, and it is very probable that the grower of exotics would find it profitable to continue them in connection with some of the rarer forms which are difficult to propagate on the usual lines. [C. T. D].
Amongst plants grown for their decorative foliage and character Ferns hold a leading place. They are not "flowering" plants in the usual acceptance of the term, but they are intensely interesting from a structural point of view. Leaving out the Selaginellas and Club Mosses (Lycopodium), there are eighty or more distinct genera in the Fern family, and several thousand species. They are to be found in all parts of the world - in tropical, subtropical, and temperate regions north and south of the Equator; and there is great variation in height, appearance, division or non-division of the fronds, the method of veining, and the way in which the spores are borne. All these are matters, however, which interest the botanist more than the general grower. At the same time the latter must have a practical acquaintance with these matters, as he is in the great majority of cases compelled to raise his plants from the spores, or "seeds" as they are popularly called. How these spores produce new fern plants has been already dealt with at p. 213, and every Fern-grower should make himself acquainted with these facts.
During the past thirty years certain kinds of Ferns have increased immensely in popularity amongst market growers. Owing to their decorative character they are in demand all the year round, and there are now many growers who devote their best energies to supplying the most saleable varieties. There are others who also grow many of the rarer kinds for private establishments where an interest is taken in keeping up a good collection of Filices - as Ferns are scientifically called.
For market work Ferns are usually cultivated in span-roofed houses varying from 100 to 200 ft. in length and 12 to 20 ft. in width. Such houses are well provided with hot-water piping and water tanks, as heat and moisture are the great aids to the market grower in producing large crops with the utmost speed and economy. Even then he selects only those kinds that will stand the rough usage of being packed off to market without too much packing, and that will also stand the draughts and chills and variations of temperature to be met with during the winter months in Covent Garden and other markets. Of course glass houses of almost any description, so long as the cultural requirements are attended to, will be useful for Fern-growing, and some very fine crops indeed are turned out every day from most dilapidated-looking structures.
Apart from heat and moisture, Ferns generally are not lovers of ardent sunshine. During the winter the British climate is none too sunny, but during the summer months it becomes essential to shade the Fernhouses heavily with limewash or other mixtures to prevent the fronds assuming a yellowish tint that would in the great majority of cases prevent the plants from being sold.
As all the plants are grown in pots varying in size from 2½ to 5 in. and 6 in. diameter, the Fern-grower is a good customer to the maker of pots. To accommodate these the houses are usually fitted up with stages made of wood battens or concrete - at the sides and centres also in large houses - and house after house is often filled with the same variety. In a market-Fern nursery plants are to be seen in all stages of development - from the spores that have just been sown to the finished article packed ready for market. There is a constant change and displacement going on, and as quickly as one house is emptied of its saleable contents it is filled with others in a less-advanced stage.