Ferns – Accommodation Requirements
There are something in the region of 9,000 fern species, growing throughout the world. The pleasure from growing them is immense, for though they do not produce exoticthey more than compensate for this by their grace, soothing colours and diversity of form. They can be divided roughly into five groups for the purpose of their cultural and accommodation requirements: the tropical group, the temperate group, the filmy ferns, the epiphytic group and the hardy group.
The tropical group
Many of these are fascinating subjects that will grow fairly easily under greenhouse conditions. The temperature range must be maintained around the 21°C (70°F) level, dropping during the winter months to 20°C (67-68°F) to eliminate the risk of etiolation through the effects of poor light and excessive temperature.
The glasshouse used must be equipped with some means by which it can be shaded during the summer from direct sunlight. Heating is best achieved by hot water, through small-bore piping. Hot air heating is not suitable for fern culture, as this dries the atmosphere considerably, and the all-important relative humidity level drops too low. Humidity is one of the most important factors to consider when cultivating ferns. The use of the capillary bench system raises the atmospheric humidity level quite considerably, while also allowing the plants to take up water themselves, thus saving both time and effort. Not all ferns respond favourably to this method of culture, many requiring a very free-draining compost or growing medium. However, a simple system of benching with a shingle, gravel or ash layer 5-7.5cm (2-3in) thick, on which the containers and plants are stood, is still a very satisfactory way of housing the plants.
The floor and benching, if of the last type, should be kept moist by damping with a can or hose two or three times per day, more damping being necessary in the summer than winter months.
Ventilation will hardly be required, and should be applied with extreme caution if at all. A little air if and when the temperature reaches 29-32°C (85-90°F) could be given, but the humidity level must be watched and the young growth not allowed to flag badly.
If space and conditions allow, one can landscape an area of the greenhouse and plant out selected ferns to give a more natural appearance. Some of the larger species, eg tree ferns, which include the Cyatheas, lend themselves to landscape work, and can be underplanted with other species, eg, Tectaria or Nephrolepis, to give a pleasing effect. This is a way of saving labour, as such a planted area will hold plenty of moisture and watering need not be carried out so frequently.
Suggested subjects: Nephrolepis spp and cultivars, eg Nephrolepis cordifolia, N. exaltata, N. davallodes; Pityrogramma spp (the gold and silver ferns); Adiantum tenerum, Adiantum raddianum.
The temperate group
This next largest group contains many very pleasing plants, and indeed some from high-altitude tropical regions also. The cool-temperate fern house requires the same general refinements as does the tropical. Blinds must be provided and an efficient heating system is necessary, although the temperature here is kept at about 10 — 13°C (50-55°F) during the night and up to 18°C (65°F) during the day, above which ventilation must be applied. Being a cooler house, the humidity level is not so critical and is easier to maintain. Plants may be grown in containers on benching, or in a landscaped area. It is possible to incorporate the two methods in one house, using the specimens from the staging as they become larger to replace old plants, or fill gaps in the landscaped section.
Many of theare good specimens for such a house. cretica and its cultivars, P.s longifolia and P. vittata are all fast-growing plants. P. altissima and P. tremula provide larger specimens attaining 60cm-1.2m (2-4ft) in height. These can all be raised from . Also suggested: Cyrtomium falcatum, Cyrtomium fortunei, C. caryotideum; the spleenworts bulbiferum, mayii.
The filmy ferns
This is possibly the most interesting of the fern groups. The plants are usually quite small and, as the name suggests, very delicate, much of the fronds being only one cell layer thick, giving the appearance of a thin film of tissue. They are exciting to grow, and some could be accommodated in the cool temperate house if grown in a closed case or frame (there are one or two designs on the market which would prove very suitable). One may, however, experience difficulty in obtaining material of these plants, due to their scarcity. A number are natives of New Zealand and they are all members of the family Hymenophyllaceae.
Humidity is particularly important for the filmy ferns. They require to be grown in a moisture-laden atmosphere, although not liking their feet inconditions. They will not take full sunlight either, so must be partially shaded on all but the dullest days. A house devoted entirely to the culture of these plants need only be fitted with enough pipe heating to exclude frost. It must have good ventilation to enable it to be kept cool, but not to lower the atmospheric moisture-level. The proven method is to have a double opaque glass roof, with the ventilation applied between the glass layers.
There are some filmy ferns which originate from tropical environments, and these would require much higher temperatures.
Suggested subjects: Hymenophyllum demissum, Hymenophyllum wilsonii; Trichomanes venosum.
The hardy fern group
This last group comprises the hardy and slightly tender species. They are natives of the colder parts of the globe, including Britain, and have to tolerate frost during part of the year, but need protection during the winter as much from excessive dampness as from cold. They may be housed in a cold greenhouse or cold frame, with some method of protection against the worst frosts.
These plants must have a dormant period in which to build up reserves, and most form a resting crown of young fronds tightly packed around the centre growing part of the plant. Water should be withheld during the winter, or applied only if the compost becomes quite dry. In this way slight frost will not damage the resting crowns.
Suggested subjects: Phyllitis scolopendrium; Adiantum venustum;aristatum.
The epiphytic group
The cultural needs of this group are discussed fully below.
General Fern Culture
A basic general compost for most terrestrial ferns consists of 3 parts by volume moss peat, 1 part by volume loam, 1 part by volume coarse sand. The peat need only be put through a 1.8cm (3/4in) sieve to eliminate the very large lumps. The loam should be passed through a 1.6m (1/4in)riddle and sterilized, preferably by steam. No fertilizers need be added to this mixture, as when the plants have fully permeated their allotted compost with roots, a liquid feed can be used to give added nutrient. To this compost, ‘pea’ gravel or granite chippings can be added for the temperate group of ferns. This gives sharper , so necessary during wet or cold spells. Special composts can be bought.
The epiphytic group requires a free-draining compost that will retain sufficient moisture without becoming waterlogged and sour. A large number of these epiphytic plants are in the family Polypodiaceae. They respond well to the following compost: 3 parts by volume moss peat, 2 parts by volume fibrous bracken peat, 2 parts by volume sphagnum moss, 1 part by volume charcoal, 1 part by volume leaf-mould or bark chippings.
The majority of ferns object to being over-potted, ie given a large quantity ofto root in, so it is usual to pot on in small stages, giving only one increase in pot size eg. 1.25cm (1/2in) at a time. There are exceptions to this, however, and a strong-growing plant during the spring and summer months will take a larger move without setback. When repotting, care should be taken not to damage the root ball, as this may cause the fronds to wilt and desiccate as a result. Some types produce a short rootstock and, when repotting, this ought to be partly covered by the new compost. Examples of this type of growth are to be found in Pteris species, eg. Pteris altissima, Pteris pacifica, P. tripartita. Others produce a creeping rhizome or rootstock which must not be buried deeply, but kept at soil level and given adequate room to spread over the soil surface.
When potting, one must be guided for drainage not only by the system used but by the plants themselves. With capillary benching no crocking is the general rule: one is aiming at a good contact between bench and compost. However, certain fern species appear to become over-wet with this method, and it is preferable to revert to the old system of crocking and placing rough peat over this, before adding the prepared compost and potting.