Fine seed should be sown broadcast — sprinkled on the surface — because if buried too deep, it will run out of energy before it reaches the surface.
Seeds have only a limited food supply to last until they form roots and begin to photosynthesize. If they are buried too deep, they run out of food before the y reach this stage and die.
The easiest way to handle extremely fine seed is to mix it with silver sand before sowing, so that it can be seem. As with any seed, always be guided by the instructions on the seed packet regarding the depth at which to plant the seed, as well as whether it should be covered.
If there is no packet, the general rule is that the smaller the seed, the less covering it needs; very fine seed may need no covering at all. After sowing, cover the? pot with a plastic bag, held securely in place with a rubber band, or place a sheet of glass over the seed tray. Place in a shady spot at a temperature of approximately 60—70°F (15—20°C) until germination occurs.
Remove the covering when germination starts, and transfer to a bright situation, out of direct sunlight. Turn regularly if the light is lopsided, to prevent the seedlings becoming drawn and bent. As soon as the young plants have two ‘true’ leaves (which appear after the first “seed” leaves), they can be pricked out into small, individual pots of soil. Handle by the leaves at this stage, not the stem, because bruising the stem now will kill the plant. Settle by watering gently, rather than pressing the soil with fingers or a dibble, because this can damage the roots.
Select a mature frond with sporangia on the underside and check the ripeness of the spores by touching them gently — a dust-like deposit on the finger indicates that they are ready. Detach the frond with a clean, sharp knife and lay it face-up on a piece of clean, white paper, where any activity is clearly visible. Keep in a warm place for a day or two, so plenty of spores are shed.
Sow the spores onto moist, sterile soil, enclose in a plastic bag, and place in a warm position with plenty of bright light, but not direct sun. Mist twice a week with sterilized water (boiled and allowed to cool) until the soil is covered with green “moss (this takes approximately 6—12 weeks). Prick out small pieces of “moss” onto sterile soil and mist with lukewarm boiled water.
Finally, seal into plastic bags and keep them in a warm, bright place, misting daily, until tiny ferns develop. These can be transplanted as soon as they are large enough to handle.
The process of loosening the growing seedlings and transplanting them from their seed tray into individual pots is called “pricking out”. Gently grip the seedling by the leaves and use a dibble to plant it into fresh soil.
- To sow very fine seed, fill a pot or seed tray with seed and cutting soil. Level the surface by scraping off the excess with a straight edge across the rim.
- Use a hoard to firm the soil vet y gently and create a level surface.
- Sieve a fine layer of soil over the top to form the seedbed.
- Sprinkle pinches of the seed-and-sand mix evenly onto the soil.
- Water by standing the tray inside a larger one containing water.