The Fern Society of Victoria Inc.

ABN 85 086 216 704

D.cycadina,
germinating
spore

Growing ferns from spore

Besides being beautiful to behold ferns also have a fascinating life cycle. Growing ferns from spore is an interesting challenge requiring little but patience and persistence.

Collecting spore is simple but it is necessary to get the timing right. Towards this end a hand lens (10x magnification) is very useful although with experience it is often not necessary. Difficulty may be due to immature spore which may not shed properly, or more commonly all the spore may have been already shed in which case only dust from the spore cases may be collected. Regular examination of a fertile frond over a period of time is useful education. Sometimes immature spore, ripe spore and empty cases may be found on the one frond.

To collect spore simply place the fertile frond on a sheet of paper. In most cases, if the spores are ripe they will be shed overnight, but leathery fronds may take longer to dry out. A small section of the frond may be used as a test to see if the spores are ready to be shed.

Separation of the spores from the spore cases can be done by gentle tapping on a sheet of sloping paper. This causes the spore cases to move down the paper at a faster rate than the spore. Separation of the spore from the spore cases is not essential if sending material into the spore bank as the spore bank has a special sieve to do the job.

The collected material should be identified with the name of the species and the collection date, and wrapped in paper in such a way that the spore is not able to escape. The folded paper packets as presently used by the spore bank is one way to achieve this. Ordinary envelopes may be used but the corners need to be turned over and taped, otherwise the spore tends to puff out through the corners.

Green spore (e.g. Todea barbara) survives for only a few days and should be sown straight away. Spore from some other species (e.g. Blechnum) may not store well. However if stored in a cool dry spot most spore will survive for a couple of years, and some for much longer.

Preparing a Suitable Medium.

Any fairly coarse, porous material seems to be suitable. Old shredded soft treefern fibre gives excellent results if available. Peatmoss, crushed terra-cotta pots, charcoal or Elkhorn fibre (or a combination of these) have also been used successfully.

Pots 5 or 6 cm square are quite sufficient to grow a large number of ferns, enabling a few different species to be raised in a relatively small space. The pots may be filled with the chosen medium or a 2-3 cm layer may be added on top of your normal potting mix. The mixture may be sterilised by carefully pouring hot water through the mix and then standing the pots in hot water, up to the rim, in a closed container for an hour. Alternatively the mix can be microwaved to give about 10 minutes of steam treatment. Over cooking the mixture should be avoided as it may cause the release of some harmful products.

Sowing the Spore

Open the paper envelope containing the spore carefully. The paper packets from the spore bank should contain enough spore to sow at least one container but may have enough for 3 or 4. If the spore are sown too heavily the resultant prothalli may have to be pricked out early to avoid overcrowding problems. To sow the spore, hold the open envelope about 6-7 cm above the pot and give it a gentle tap to allow the spore to float down onto the top of the mixture. This must be done in a perfectly still room, completely free from any draughts or breezes.

Conditions for Germination.

Spore may be sown at any time of the year, but germination will be faster in the warmer months of the year. For successful germination spore must be kept moist at all times. This is simply achieved by placing the sown pots in a closed container (e.g. plastic ice-cream container, food crisper, glass aquarium covered with a sheet of glass, or just placed in a plastic bag). Provided the container is reasonably well sealed the pot should remain moist almost indefinitely. If it becomes necessary to add water, stand the pot in cool boiled water, watering from above may wash spores away. The pot should be placed in a well lit position but not in direct sunlight. In a warm well lit position germination usually occurs in about 4-6 weeks and appears a very small green specks which gradually grow into flat heart structures (prothalli) about 1/2 to 1cm in diameter. The initial growth may be mistaken for moss. Germination may take several months if conditions are not good.
Some spore require the presence of microbial organisms for successful growth, and the spores of a few of the less common species will only germinate in the dark.

The prothalli, which are the intermediate stage of the life cycle of the fern, may be mistaken for moss or liverworts. They are small flat green structures, afew millimetres in diameter. Each has a male and a female portion located on the underside, the male portion releases sperm which swim across to fertilise the egg. The fertilised egg then starts to grow and produces the fern proper. The first appearance of fronds may vary from 2-3 months in very rapid species to years.

Most problems result from overcrowding of the prothalli (from too heavy sowing) or from contamination due to poor hygiene. Fungi, mosses, algae may overgrow or damage the prothalli. Overcrowded prothalli may be pricked out into another container as soon as the problem is noticed. Fungi may be controlled by spraying with half strength Benlate provided the prothalli are a reasonable size.

Mosses and algae are best avoided by careful hygiene - proper sterilisation of the mix and only using water which has been boiled. An open loose mix helps to avoid algal growth.

Pricking out and Potting on

The thickness of the growth of the prothalli will often determine when to prick out. If the surface of the mix is heavily covered with prothalli pricking out should be done at this stage, pricking out small clumps of prothalli into a mix prepared and sterilised as for the original sowing. Usually pricking out is done when the sporeling has one or two fronds although it may be done at any stage. The young ferns may be transplanted into standard propagating mix, or into a mixture of about 2 parts peat moss, 2 parts washed river sand and 1 part mountain soil.

The sporelings should first be hardened off by gradually exposing them to air, and then, after transplanting, placing them under glass or other cover until they have settled down when they can be again gradually exposed.

It should be possible to lift the little fern off the pot with its prothallus still attached. At this stage true roots will usually not be well developed, and the prothallus can be gently pushed down onto the surface of the new pot or tray to support the tiny fern plant. This should be done fairly quickly and in a cool, draught-free location as the delicate young ferns will not survive for long out of the humid atmosphere they are used to. As soon as possible, transplanted sporelings should be very gently watered and placed under glass again. Treatment with a product such as 'Maxicrop' or 'Plant Starter' will assist establishment of the new plant.

If the sporelings are allowed to grow too large and crowded before they are picked out, they may be scooped put in clumps with a spoon, placed in a saucer of water, and then gently separated and planted into tubes or trays. Again they should be replaced under glass without delay.

The newly transplanted sporelings should be allowed to develop under glass until their fronds are about 5-10 cm high. At this stage they may be very gradually acclimatised by slowly raising the glass cover, a few millimetres at a time, over a period of about two weeks.

Using the techniques outlined above, it is not unusual to grow one or two hundred ferns from each 5-6 cm pot sown with spore.

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