Propagation of Ferns
The quickest way of increasing one’s stock is by vegetative propagation. Not all ferns lend themselves to this, however, but many may be so treated.
Quite a number of the ferns produce bulbuls on their mature fronds. In many cases, the frond or part of it with the bulbils attached can be removed, pegged down on to a peat/sand growing medium, and placed in a propagating case for rooting to begin. When the plantlets have become established, they can be removed from the frame, separated and potted into general compost, thereby taking about 18 months to become mature plants. Examples of species that can be propagated in this way are: bulbiferum, viviparum, Diplazium proliferum, Tectaria incisa (viviparous var.).
The great majority of epiphytic ferns colonize new area by means of rhizomes. These can be separated from the parent plant, preferably with a quantity of root intact, and attached by wire pegs to the medium on which they are to be grown, or tied to cork bark or other material if being grown in a truly epiphytic manner. It is not necessary to place it in a propagating case, unless the piece is small or weak, or a shy plant to establish, eg. Oleandra spp, Pyrrosia spp, Microgramma spp.
Rhizome propagation works very well foraureum, Drynaria sparsisora, species of Davallia in general, and some members of the genus .
The best known group which exhibits this feature are the platyceriums, or stag’s-horn ferns. Not all the platyceriums produce root buds, but a number including Platycerium stemmaria, Platycerium bifurcatum and Platycerium alcicorne do so quite readily. When the young plantlets resulting from these adventitious buds have produced their sterile ‘nest’ frond, they may be removed and potted into a 7cm (2-1/2in) pot, or placed immediately on to a piece of cork bark, on which has been placed a small cushion of sphagnum moss and osmunda fibre to accommodate their roots. Eventually they may be transferred to a larger pot or board, or even planted on a rock area to grow to maturity.
Diplazium esculentum produces a mass of young plantlets around the parent, and, if grown in a container, these can be cut out with some root and, potted singly, and will quickly make mature specimens.
This method of propagation can be applied to many species and groups, usually rhizomatous. All that is needed is to slice up the plants. In this way a pan of, say, Dennstaedtia or Drynaria can be divided into halves or quarters, provided sufficient young growth is left in each section. The sections can now be potted or panned into a container of appropriate size and allowed to settle down and colonize their new home. No initial establishment treatment is necessary.
Anyone who has become interested in fern growing will sooner or later want to try to raise plants from. These are tiny dust-like bodies, which can be compared loosely to the seed of higher plants. The germinate to form prothalli, small and usually scale-like. The prothallus is the sexual stage in the life-cycle of ferns, where fertilization takes place. The frond- and spore-bearing fern-plant grows up from the prothallus.
Raising ferns from spores
The best time of year for sowing is roughly from early spring to early summer inclusive. It may be carried out later than this if need be, as the life of some spores is very short and it is possibly better to sow than to store for a long period. There are a number of different methods for raising plants from spores. The following gives good results, provided one pays attention to hygiene.
1. Sterilize sufficient pots for the number of items to be sown. Clay pots are preferable.
2. Fill to within 1.25cm (3/4in) of the lip with compost which should contain the following parts by bulk (each part should be sterilized to 180°F, preferably by steam) screened through a 0.3cm (1/8in) sieve: 3 parts moss peat, 1 part loam, 1 part sand. Put one crock (piece of clay pot) over thehole, to stop the compost falling through. After filling, firm slightly with a firming tool (cut a circle of plywood to the required diameter and affix a handle to it).
3. Write labels for subjects to be sown. Plastic T-shaped labels are best, as they allow the covers to sit neatly on the pot rims.
4. After the pots have been prepared, water thoroughly with boiling water, which can be applied through a metal can with fine rose attachment.
5. Immediately (4) has been completed cover the pots with glass covers (convex watch-glasses are best, but plastic or glass petri dishes can be used; failing this, squares of ordinary glass will suffice).
6. The spore-bearing material, which has been previously collected and dried to allow the spore-cases to dehisce or break open in the packet, may now be sown. One pot is sown at a time, and the glass or plastic cover replaced as soon as sowing is complete. Only a thin dusting of spores is necessary to give the best results. Heavy sowing will cause overcrowding of the prothalli, often resulting in maleonly being produced. Thus fertilization cannot be achieved as early as is desirable and fungal infection is more likely to occur.
7. The sown pots are now placed in plastic watertight trays. A solution of potassium permanganate is poured into the trays to a depth of 125-2cm (½-3/4in), to suppress any algal and fungal growth. To make up this solution, enough permanganate crystals are added to a gallon of water to produce a deep mauve colour. The plastic trays should be kept topped up with the solution as needed. The depth of solution in the trays should not exceed 2.5cm (1in); more would cause water- logging of the compost in the pots. The trays can now be put in the greenhouse, and kept under the staging in partially subdued light, and if possible raised above the ground by some method. This reduces water splashes and prevents water from the dampening process from entering the trays and contaminating the permanganate solution. A green flush of growth will be noticed in some pots after 4-5 weeks. Speed of germination depends on the temperature in which the pots are placed: 18-21°C (65-70°F) for the tropical subjects and around 15°C (60°F) for the temperate ones is adequate. This is the stage when fertilization takes place, and as a result the sporophytes (young plants) will start to appear. The plants must now receive more light, and so can be moved on to the benches, but still kept in the trays, to absorb water from beneath. As the sporophytes develop, the covers on the pots may be gradually removed, and eventually the young plants ‘patched off’ into shallow trays, pans or small pots, depending on the quantity of plants needed. It is better to include three or so plantlets in each group or patch, placing nine or so patches per 10cm (4in) pan. With the tree ferns, eg Dicksonia spp, Ciborium spp. Cyathea spp, a single plant should be selected, as a strong single-stemmed specimen is required.
When the patches have filled their allotted space they may be potted on. Each group can now be placed in a 5cm (2in) pot, containing the general compost mixture, except for epiphytic plants, which require a more open growing medium. As the plants develop, potting on can continue in stages until a pot about 13cm (5in) diameter has been reached. By this time the majority of ferns will be producing spore-bearing fronds, thus completing their life cycle.