How to Sow Staghorn Fern Spores: Collecting, Sifting, and Telling Gametophytes from Moss

Spore sowing is slow; know the timeline first

Staghorn fern (Platycerium) sporelings are grown from spores. A few weeks after sowing, gametophytes (prothalli) appear; a few months later come the first tiny fronds, and the first proper shield frond usually takes one to three years (see pups, sporelings and tissue culture). It is where breeding and selection begin. If you want to save time, start with a pup or a young plant that already has true fronds.

Collecting spores: wait for the patches to turn brown

Spores form in the spore patches on the underside of the fertile fronds. When ripe they turn from green to brown and look like a layer of felt. Cut off a small piece, lay it on white paper and leave it indoors out of drafts for a few days; the spores drop as a fine golden-to-tan powder. The less spore-case debris mixed in, the better.

Sifting and sowing: test-sift on a card first

Spores are extremely fine. Poured straight onto the medium they pile up in a heap, and the gametophytes come up crowded, competing for space. Sifting them through a fine mesh lets them fall like a thin dusting.

1. Test-sift: sift once onto a small paper card. If almost nothing passes, the mesh is too fine or there is too much debris; change the mesh or clean the spores again.
2. Prepare the medium: finely chopped peat or sphagnum, moistened, then sterilised with boiling water or in the microwave and left to cool. Use a clear container with a lid.
3. Sow: tip the spores back into the sieve, hold it over the medium and tap it gently. A thin dusting is enough; do not cover with soil.
4. Close it up: keep it warm in bright, diffuse light, out of direct sun, and below 32°C inside the box.

The green that appears: gametophytes or moss?

A sealed, humid box in diffuse light suits moss just as well. Look closely. Gametophytes are flat, slightly translucent, heart-shaped pieces pressed against the surface, like a thin green film. Moss is three-dimensional, with fine stems and tiny leaves standing up in fluffy tufts. Photograph it close and in focus; even experienced growers cannot tell from a blurry picture.

If it is gametophytes, lift clumps onto a fresh box of medium to grow on, giving them room and moving them away from whatever else is in the old box. If the whole box is moss, there is no point waiting. Sifting the spores and sterilising the container and medium beforehand cuts down on moss a great deal.

Once the gametophytes have filled in, mist them now and then with boiled and cooled water so the surface carries a film of water: fertilisation needs it, and only after that do true fronds start to appear.

Do not leave it alone

Open the box every so often while it is sealed, sort gametophytes from moss early, and divide into new boxes when needed. For care once true fronds appear, see caring for sporelings and potted seedlings; to cross two chosen parents, see checkerboard placement for crosses.