Raising ferns from spore is a simple and easy means of increasing your plants or adding new ones to your collection.
Most spore remain viable for a long time with the exception of the Osmunda family and one or two other lesser known species that produce green spore and remain viable for just a few days or for a few weeks.
Fern spores are microscopically small and germinate on the soil surface. The first requirement is moisture which must be continually present for germination and subsequent fertilization to occur. Secondly, the growing medium must be free of pests, soil pathogens and weeds. Mold or moss can take over the soil surface and smother the germinating spore.
Spore produces an alternate generation in the form of a tiny prothallus. This produces eggs and sperm, and from the fertilized egg, a tiny new fern plant begins it’s life.
HOW TO SOW
I use 2 1 /4 inch pots of the soft plastic variety. Larger pots produce many more plants than one would want. Hard plastic pots shrivel when boiling water is poured over them.
Fill the clean pots with sterilized potting soil, gently firming to 1 /4 inch of the top of the pot. Place the pots in the sink, cover with a paper towel and slowly pour on a kettle of boiling water so that the water goes right through the pot of soil.
When the pots of soil have cooled, remove the paper and sow the spore. Place the pot in a plastic "baggie", tie with a "twistem" and label, noting the name, date and source of spore. Put the bags in a bright window away from direct sun or under grow lights. They will need no further attention for several weeks when they can be sprayed with water and the bags checked for leaks.
Several weeks or months may elapse before the green prothalli are visible. These develop rhizoids or hair like roots that take up moisture and anchor the prothallus to the soil. When fertilization takes place, tiny fronds appear and live on the green prothalli until they develop their own roots. These new fern sporelings can be lifted out and potted up separately and enclosed in a baggie for a short time. Gradually open the bag to harden the plants off.
There are other ways of growing fern spore, but for me this method is satisfactory. Sterile pots, soil and strict attention to cleanliness are most important.