It will come as no surprise to readers of this blog that I’ve developed a slight obsession with ferns of late, centred on both tracking down and identifying wild ones and growing them at home. Despite that, I hadn’t yet tackled the seemingly difficult process of growing ferns from spores. At least, not until this year.
Fern Biology
Ferns are among our most primitive plants, and their reproduction, while fascinating, is less sophisticated than that of flowering plants. Cutting a long story short, spores are produced on the underside of the frond in structures called sori (or a sorus if referring to just one).
Ferns are interesting in that they have two distinct life stages. The first is the gametophyte, or sexual stage, in which the spores grow into a curious, shield-like structure called a prothallus. It looks a bit like a tiny green fish scale and, in truth, rather resembles a bryophyte, but with minute pockets that hold the egg and sperm. When conditions are right, fertilisation takes place, with sperm swimming through water droplets to reach the egg of another prothallus. Only after this stage does what we think of as a “proper” fern develop, as the plant enters the second phase of its lifecycle.
Keen to try this myself – and having sufficiently swotted up with a range of fantastic resources online [here] and [here] – I decided to give it a go this summer. Time for an update!
Gathering Spores
Ferns produce spores at different times of the year, though most seem to be ready between June and September. It’s fairly easy to tell when they’re ripe: in most species, the sporangia curl back or fall off entirely, revealing brown, yellow, or even black dust – the spores. Gathering them is incredibly simple. You can either tap a fertile frond over a paper envelope or collect a small section of the frond; a little goes a long way. If you choose the latter, it’s best to let it dry on some paper for a few hours, after which you’ll notice the spores beginning to fall and gather on the surface.
For this little experiment, I gathered spores from a mix of cultivated plants growing in the garden including Brittle Bladder-fern Cystopteris fragilis, Rustyback Asplenium ceterach, Soft Shield-fern Polystichum setiferum, Scaly Buckler-fern Dryopteris remota, and Beech Fern Phegopteris connectilis; as well as a few common wild species growing in public spaces (remember, you need permission to collect even the smallest hint of plant material from private land). In the end, this meant I collected spores from Western Scaly Male-fern Dryopteris affinis subsp. affinis, Borrer’s Male-fern Dryopteris borreri, and Maidenhair Spleenwort Asplenium trichomanes too.
Sowing the Spores
Having gathered our spores, it was time to sow them. This, it seems, is the stage you really need to get right. First, you need an airtight container that seals in moisture and provides the humidity required for the spores to germinate (we used a multipack of cheap plastic Tupperware). Secondly, you need a fine, sterilised compost. We opted for a fine seed compost, zapped in the microwave for three minutes to kill any nasties lurking in the soil. Other sources suggest that pouring boiling water through the compost or placing it in the oven works just as well.
With your materials prepared, all that remains is to sprinkle on your spores, give them a good spritz of water, label the container, and replace the lid before leaving it somewhere bright for nature to run its course. In our case, we placed all our containers under fluorescent grow lights used for our houseplants.
Watch and Wait
Next comes the hard part: ignoring your containers until you notice signs of life. I didn’t manage this perfectly, which may explain some of the problems mentioned later in this post. Generally, sources online suggest that different ferns take varying amounts of time before any activity becomes visible. I was pleasantly surprised that after only a month, each of our test containers hosted a fine, green, algae-like film spreading across the soil. This was the first sign that our spores were starting to grow into prothalli.
Watch the Prothalli Grow
Eventually, after a variable amount of time depending on the species (around three to four months for most of ours), the initial green, algae-like growth began to transform into the shield-like structures recognisable as prothalli. At this stage, the fern grows its first roots and begins to photosynthesise, and it is also the point at which the all-important fertilisation happens, if you’re successful. To help with this, sources recommend a regular spritz of water to aid cross-fertilisation, something that would normally be provided by rain outdoors but must be administered manually when growing ferns indoors. The photos below show a range of more advanced prothalli.
After some time, these prothalli develop into the sporophyte generation, the form we most closely associate with ferns.
Signs of Life
Fast forward to early winter and most of our ferns have now begun transitioning into their sporophyte generation. Some, such as Beech Fern and the larger Dryopteris species, are lagging behind, with only the tiniest hint of their first fronds visible. Others are positively romping away, particularly Brittle Bladder-fern which has already warranted the relocation of larger plants to individual pots (again in sealed containers) for growing on over winter. I have also been impressed with Soft Shield-fern.
As we now have so many young ferns growing in containers, we have broken with the usual advice that recommends leaving sporlings in place until they are large enough to handle. Instead, we have opted to split our batches, leaving some in situ while moving small clumps of prothalli to individual containers to see whether this results in healthier, more vigorous plants. All are being kept under plastic to retain that all-important humidity, but I have already begun removing the lids from larger specimens to gradually accustom them to harsher conditions, with the aim of moving some outdoors come spring.
The images below show various species as of 20 November 2026, which is not bad at all for spores sown in June and July.
A Few Problems
While some of our ferns have been successful, others have failed miserably, and in most cases, this is entirely my fault. I mentioned earlier that you should ignore your spores for a prolonged period, something I confess I didn’t do, as too often I found myself opening the pots for a sneaky look. Doing this, it seems I allowed contaminants into the pots, resulting in mould that quickly overtook many of the young plants. We lost most of our Rustyback specimens this way, but I did discover that you can safely move prothalli to another jar, helping to preserve at least some plants.
Not sterilising the soil sufficiently may also have been a problem, as algae and bryophytes appeared in several pots, leading to competition with the young ferns. The greatest problem of all, however, seems to be overcrowding. It is all too easy to sow far too many spores in a single container, and when this happens, the added competition prevents the prothalli from developing properly. This is currently affecting our Dryopteris affinis containers, but I hope it can be remedied by thinning, just as you would with the seedlings of any other plant.
And with that, the first stage of the challenge is complete. I will post an update further down the line as we progress to potting on and eventually planting out. I am optimistic, as the whole process has been far easier and, dare I say it, quicker than I envisaged at the start. If you have ever fancied growing ferns from spores yourself, I would strongly recommend giving it a go. You may find it slightly addictive and end up with more than you can handle, just as we have.
As a quick further update since drafting this post, we ended up sowing spores from a range of other cultivated species, including Oak Fern Gymnocarpium dryopteris and Limestone Fern Gymnocarpium robertianum, as well as some Narrow Male-fern Dryopteris cambrensis gathered from an unassuming Northumbrian roadside. Being more ambitious, I am also attempting to hybridise Male-fern Dryopteris filix-mas with Borrer’s Male-fern to create Cryopteris × critica, but we will see how that pans out.
