by Brian Aikins, firstname.lastname@example.org
Posted on Fernet, 2 October 1997
Reproduced with permission.
One of the pages we are planning
to put on this site is about growing ferns from spores. Brian Aikins
posted this excellent article to Fernet, and I asked if I could use
it instead of duplicating his work. Here is his article.
Developing sporangia on the underside
of mature fern fronds start out green and gradually turn brown, black,
or yellow. After ripening and releasing their spores, the sporangia
look fuzzy and slightly pale. Ripe sporangia have the most intense color
and look firm or very slightly fuzzy. Place a portion of the fern frond
having ripe sporangia in a loosely closed white paper mailing envelope
and let dry at room temperature for about 2 days. Species with green
spores must be sown within a day or two of being shed. Spores of most
other species are viable for a year or more. Their viability can be
extended by keeping the spores in the refrigerator (about 40ºF).
I use a 50-50 mixture, by dry uncompressed
volume, of Canadian peat moss (sometimes sieved through 1/8th inch screen)
and washed sand having 1/16th inch grain size. Crushed perlite of the
same size can be substituted for sand. Perlite has some advantages:
it holds water, it reflects light, it might have less contaminants than
sand and it usually crushes instead of denting or scratching. Sometimes
I add 1/16 teaspoon of ground dolomite per cup of dry peat moss to partly
counteract its acidity. After adding tap water (about 50% of total dry
volume), 'sterilize' using microwave (4 minutes per cup of mixture in
a 800 watt oven) or pressure cooker (25 minutes at 15 psig). Pouring
boiling water through the soil also works but leaves the soil a little
too wet. Other media I have tried include commercial potting mix, milled
sphagnum, vermiculite, crushed terra-cotta, filter paper, rockwool,
agar, and weak fertilizer solutions. The peat moss/sand mixture is hard
Wash sowing containers
and all utensils
I use 2.75 inch diameter by 1 inch
high clear plastic fishing lure containers with stacking screw-on lids.
K-mart and Pay-Less sell them. Instead of stacking, I just use the top
one as a clear lid. I suppose you could save room by using them stacked
with side lighting. Any plastic or glass container covered with plastic
wrap would also work well. I've tried using 20mm diameter by 60mm high
borosilicate glass vials with rubber lined screw-on lids but growth
was slow and early transplanting was required. The obvious advantage
of glass is that the soil can be sterilized while in the container.
All equipment should be disinfected using either heat or clorine bleach.
If it can withstand heat (fishing lure containers cannot), boil for
5 minutes. If not, soak in 10% bleach solution for 30 minutes and rinse
once or twice with previously boiled water.
into sowing containers
Fill each container with about 1/4
inch deep of soil. One cup of soil is enough to fill 15 to 18 fishing
lure containers. If the soil is warm while you transfer it to the sowing
container, rising air currents help prevent contamination. It's best
to do this, and actual sowing of spores, in a room that is unlikely
to have airborne mold spores. My success rate seems to vary most due
to this factor alone. Someday I hope to build or buy a positive pressure
hood for this work; or maybe I'll disinfect the interior of a walk-in
closet and use it strictly for fern sowing.
Set up sowing
Prepare a table for sowing spores
by wiping it down with 10% bleach solution. I place the following items
at hand: #2 natural bristle artist's paint brush, 3 inch artist's spatula,
clean smooth white paper (childrens finger painting paper) cut into
2 inch squares, and heat gun or blow dryer.
Separate spores from chaff by putting
the shed mixture on a paper square and tapping while tilting the paper;
the spores stay behind while the chaff bounces forward. Better separation
can be had by sifting the mixture through a fine stainless steel mesh
(40um openings). Use the spatula or brush to pick up or brush off spores
into sowing container. Sow thinly so that crowding does not require
transplanting (drop from about 2 inches a volume of spores equivalent
to approximately 1/64th of an inch cubed). Be sure not to open the sowing
container for more than a few seconds. Use the hot air gun (set to 250ºF)
or the hair dryer to heat the spatula and/or brush between sowings.
Place spore containers
in warmth and light
I keep temperatures between 60º
and 80ºF by placing them about one foot below two 40 watt 'cool'
or 'warm' fluorescent tubes with a white painted reflector. These can
be left on 24 hours a day or turned off during warm hours to keep the
Wait for ferns
If the sowing container is sealed,
no watering is necessary. The fishing lure containers are almost air-tight
and only need watering about every 2 months. If watering is necessary,
mist with distilled water; or if growth is yellow, add 1/4 strength
nitrogen rich fertilizer. Gametophytes (prothallia) first appear usually
in 2 to 4 weeks (6 months maximum for some species). The first fronds
(sporophytes) appear about 6 to 12 weeks later (up to a year later for
some species). Since fern fertilization requires liquid water, I usually
mist with distilled water when the gametophytes are about 1/8th inch
When fronds have reached about
3/8 to 3/4 inch high, transplant using tweezers into small pots of peat
moss or potting soil and keep in a mostly covered container. I transplant
into .75 inch square seedling pots and place in a "mini-greenhouse"
--11 x 22 x 2.5 inch plastic trays with snug-fitting clear covers.
Mold and algae growth can be controlled
by lightly misting with a solution of 1/4 teaspoon Physan per gallon
distilled water. Physan-20 is benzalkonium chloride; other brand names
are Physan, Green-Shield, Barquat MB-50, BTC, Roccal, Zephiran, Consan,
and RD-20. I usually transplant individual ferns instead of fern clumps
in order to observe the growth characteristics of the individual plants.
Growth and survival rates are similar with either method.
Start hardening them by removing
some of the cover so that relative humidity drops to 60%-80%. Aseptic
technique is less important after they are transplanted. During the
first year or so, as the ferns begin to mature, they gradually start
requiring the environmental conditions of the full grown plant. For
unfamiliar ferns, I always transplant about 2 or 3 times as many as
needed to cover losses during the first 2 years. By the end of the first
year, most medium-sized ferns fill 2.5 inch pots and have fronds 4 to
12 inches long.
Save unused contents
of sowing container
Most left over gametophytes and
ferns can be kept indefinitely (8 years and counting) if kept in a cool
moist dimly lit place. I put all leftovers in the same sealed clear
plastic tackle box that is kept on a shelf about 6 feet from a window
in our basement. Temperatures range from 40º to 65ºF. No attempt
is made to use sterile techniques. Although the plants do not grow,
most stay healthy and can be transplanted at any time.