Ferns from Spores

I usually start my fern spores with regular potting soil, but I use fresh mix, not re-used from old pots. Even better is to sterilize the mixture by pouring boiling water on it or putting the moist mix into the microwave for 2 minutes and waiting for it to totally cool.  You can use a small flat, or a 4-6 inch pot.  The best flat is a plastic take-out container with a clear lid. Moisten the soil if it is dry, pat it down, and crumple the fern frond over the surface. If the frond was in a package, it makes sense to use a gentle water spray to wash out any spores that stick to the package itself. Then spritz the soil surface with water. Do not cover the spores with any soil.

Put the pot/flat into a plastic bag, and loosely tie it closed.  Again, best results are obtained with a tight lid*. You want high humidity and minimal air exchange.  Put under light, near a north or east window, or outside (if you wait until spring to start).

Check frequently, and mist the surface to keep it moist, not wet. You will need to check and mist frequently if you do not have a lidded flat. Within 4-6 weeks you should see little green moss-like growths – the prothalli. Sometimes they look like liverworts. This is the sexual stage of propagation, and it is critical that the surface of the soil have a thin moisture layer, so keep misting. If all goes well, you should start seeing “real” fern like leaves beginning to show in another few weeks – these are the asexual fronds that you want. Real liverworts are not a serious threat if they develop.  Molds are a concern and sometimes need to be scooped out.

Transplant the babies carefully, in clumps, to small pots with well drained mix. If you leave them in the original flat they will crowd each other out. Sometimes I move a few teeny ferns, but keep the original pot misted and in plastic and more ferns continue to develop. The highest loss of ferns is in the transplant stage. Do not put them into a large pot, or the soil will get too waterlogged for them. You can pot several small ferns in one larger pot, if that is all you have. Or move the entire mass to the middle of a somewhat larger flat/pot and let it continue to expand. Start them out in high humidity (in a bag) and slowly wean them to regular air with misting before you move them outside. Transplant to final location when they have at least 3-4 fronds over 2 inches long.

* The tighter the lid, the less need to open and mist. Tip: put a label both inside the flat, and outside on the lid! It is easy to lose or render illegible a tag during the long incubation period.

Rosemarie Parker/ Finger Lakes Native Plant Society  2020