Spore Propagation - Gametophyte to Sporeling

Having successfully sown our spore and placed the pot in a suitable position we sit back and start the clock. Depending on the freshness of the spore and the climatic conditions it may take from 1 to 6 weeks for some form of physical indication that the spore is germinating. But what does the germination process involve? What is actually going on? In this section we will briefly look at the germination process and in more detail will describe how we can nurture our dormant spore through to the baby tree fern stage.

So after roughly 6 weeks you ought to start seeing a green fuzz appear on the surface of the soil as shown in the image below. This green fuzz is made up of thousands of individual gametophytes. Each one has developed from the individual spores and will ultimately grow to produce a male and female sex organ on its underside.

On this image below you can clearly see how the gametophytes are developing into heart shaped discs. Each one of these gametophytes below is less than 2mm in width. At this point in its development it is crucial to ensure that the soil surface does not dry out. A very careful misting may be required just to keep the humidity high. The downside here is that if you mist too often or too heavily you may encourage rot and some species appear more prone to rotting than others so keep it minimal.

Depending on the species it may take between 2 and 6 weeks for the gametophytes to reach maturity. This image below is of a mature Cyathea rebeccae gametophyte which measures roughly 3mm in width. Here we can be fairly certain that it is ready to be fertilised. The fertilisation process quite literally involves the sperm travelling on the underside of the pad to the egg. Remember that this gametophyte has produced both its own egg and sperm and so in effect is fertilising itself.

The sperm cannot travel to the egg without the assistance of moisture through which it swims so we can encourage this by carefully misting the surface. Again, not too much - just enough to moisten the surface and most certainly not leaving any residual water to pool. The timing at which you do this is by no means crucial. Fertilisation often takes place regardless of whether you choose to mist the pot provided there is sufficient moisture.

Once fertilisation has occured (for which there is no visual clue) it is not long before the first signs of the baby tree fern become apparent. This baby tree fern is actually known as a sporophyte though is often referred to as a prothallus or sporeling. The image below is of a very young sporophyte whereby we can clearly see the first frond emerging from the underside of the gametophyte. Interestingly, the new fern is growing as an entirely seperate plant from the gametophyte and is hitching a ride in these early days.

Reaching this point in the spore growing process is usually a seminal moment for the grower. Finally all of the laborious sterilisation of soil and pots combined with the mind-numbing wait for any signs of success are rewarded with this first tiny little frond which looks more like a little green hand than a miniature frond. The road to this stage can be rocky however and frought with danger from mold, algae or rotting. This is why it is absolutely essential that you do not allow foreign matter to enter into the spore pot. Even the water that you use for misting the pot must be sterilised by boiling and allowed to cool down. I fill my spray gun with boiled water from the kettle and allow it to cool with the sprayer cap firmly screwed tight.

Should algae appear on the surface of your pot during the development of the gametophytes it is not necessarily a disaster as the gametophytes will keep growing but mold will usually signal the end of the campaign. Ensure that you lift the propagator lid or open the plastic bag as infrequently as possible so as to minismise the risk of nasties getting in and also keep an eye on the temperatures, avoiding extremes which will slow the development.

If you've got this far with no setbacks then it's time to rejoice - the next bit is even more fun!