Ferns have a wide geographical distribution, their species and varieties in nearly 10,000 different kinds being found almost throughout the whole world. Stretching sparsely from the Arctic to extreme density in the tropics, these flowerless plants favour islands and coastal areas more than inland territories.
Usually they flourish under moist conditions, especially in the highland districts of the tropics, the majority being shade loving, and a few strictly aquatic. Species vary from minute moss-like plants a fraction of an inch high to palmlike giants towering to 80 ft. or more in the misty, cooler districts of the subtropical forests. Many of these tree ferns have spread to the more temperate-regions and are to be found in the favoured coastal areas of New Zealand and Australia.
Some are epiphytic and live a mistletoe-like existence in the rain forest, entangled and entwined with vines and climbers, where they provide a snug retreat for the enormous tree spiders that infest these areas.
These ferns of the tropics and sub-tropics are theferns of temperate zones. To cultivate them successfully it is necessary to emulate the conditions under which they grow naturally and to endeavour to foster in the greenhouse the moist, humid, sunless but light conditions so essential to their well-being.
THE FERN HOUSE
There are species that will grow in a greenhouse containing a miscellaneous collection of flowering plants, but when a choice and interesting assortment is desired, it is preferable to devote a house to ferns alone.
The house should be sited with a northern exposure and be shaded from the south, thus ensuring long daylight with protection from scorching sunshine. Though ferns appreciate shade, ample light is necessary in order to develop colour and substance.
The average summer temperature (built up by sun heat) of such a greenhouse is about 60° F. (16° C). This will certainly drop in autumn, when the house should be kept cool and drier; coddling the plants is unnecessary and undesirable, although the house must be kept frost-proof. During the winter, therefore, provide sufficient artificial heat to exclude frost. Too much heat will encourage premature growth, especially in maidenhair ferns.
A minimum of warmth only is required in mild weather, raised during cold spells to an average temperature of 45 to 50° F. (7 to 10° C).
Any form of heating can be employed, including oil stoves, but oil fumes affect some plants, so keep the stove scrupulously clean and use only the best oil. Electricity is the easiest to manage and maintain.
Never allow the atmosphere of a fern house to become hot and dry; give air whenever possible during the growing season (roughly from March to September). Water the plants freely, gradually decreasing the supply at the approach of autumn until winter, when very little water will be required, and then only when dryness is obvious.
CULTIVATION OF FERNS
As in the case of hardy ferns propagation is a job for the specialist, and most amateurs will buy their specimens already potted. The ferns will, however, need repotting from time to time. In a heated greenhouse this can be done at any time of the year.
When a fern has completely filled its pot with roots, move it on to the next size of pot. Be sure the pot is clean inside and out, and place crocks in the bottom to ensure good. Use soil that is similar to that in which the plant would grow in its natural surroundings. It should be light, fibrous, spongy and capable of retaining moisture without becoming soggy or solid. Good materials are clean fibrous , , granulated sphagnum peat, , silver sand, and granulated charcoal or brick rubble. Experience will show what proportions are best for any particular type of fern. Always plant loosely.
The plants listed on this site are all suitable for growing under the conditions described. Those species that demand continuous heat the whole year round are not included.
Too often the range of ferns seen in an amateur’s greenhouse consists solely of the plants most commonly offered for sale in shops, including Pieris cretica, Cyrtomium falcatum, Asplenium bulbiferum and Adiantum amentum, all excellent plants. Although they provide a good backbone for a collection, some of the following will widen the scope.