Growing ferns from spores – a basic practical guide

STEP 1 – Prepare the sowing pots

Clean a suitable sowing container

Suitable containers include small plastic pots, translucent plastic boxes or cut down milk bottles. Ensure they have drainage holes.

Fill with compost to 1-3 cm below rim
Ferns are not generally fussy as to compost – however, peat based is ideal and coir is often not suitable. Do not add any fertiliser at this stage.

Water and sterilise
Sterilise by placing kitchen towel over the tray and pouring boiling water over to thoroughly soak the compost.

Allow to cool
Allow to cool completely before sowing. Remove the kitchen towel immediately prior to sowing.This will remove any stray weed spores that may have landed while the tray was cooling.

Spore pans V2

STEP 1 – A range of containers suitable for spore sowing

STEP 2 – Sow spores and monitor

Sprinkle spores over surface of compost
Thin and even sowing is ideal. Spores are VERY small and dust-like – a small speck goes a long way.

Place in clean, sealable plastic bag, label and keep out of direct sunlight
After sowing each pan, place in a sealable plastic bag and wash your hands to reduce cross-contamination.

Look for the formation of prothalli (see pictures)
Spores do not grow directly into ferns. Initially prothalli are formed. They may form after a few weeks or a few months or even a year after sowing. Be patient!

Look for the formation of small fern plants
Eventually the prothalli will be replaced by small fern plants. This should happen naturally, but may take some time. Something that may speed this process up is spraying with sterilised water if the pots look dry. Something that slows it down is the prothalli being too crowded – try taking out some and hence making holes in the blanket of growth if the spores have been sown thickly.

Little intervention should be needed during these stages  

Prothalii 2 V2

STEP 2 Three examples of fern development. Prothalli just forming, prothalli well grown with true ferns just starting, and prothalli replaced by small fern plants 

STEP 3 – Separate out small fern plants

Prepare pots
Ensure pots/modules are clean and fill with compost.  The same composts can be used as for sowing. Again, additional fertiliser is not normally required.  Water the pots and allow to drain overnight. Choose pots or modules suitable to the size of the plants and of the bags you intend to use.

Prick out individual ferns, or clumps
Pricking out is the process of separating individual plantlets, or clumps, and potting these into small modules to grow on. Ideally, prick out when the fern plants have several leaves and are clearly growing. Pricking out when very small is possible, but tiny fern plants will need delicate handling and aftercare.

Place in clean, sealable plastic bags, label and keep out of direct sunlight
Once potted and sealed, the little fern plants are again fairly trouble free and should be left to grow. They can be slow and it may be up to a year before you will want to pot them on again

Patchings and pottings V2

STEPS 3 & 4 – Spore pan ready for pricking out, and a tray of small plants reading for potting 

STEP 4 – Pot up fern plants

Pot up the small plugs into larger pots, label and keep out of direct sunlight
This is one of the trickiest stages of fern spore growing. This is because the fern plants have been in their own microclimate in the plastic bag since sowing and it’s stressful to be introduced to the outside world. Wait until small plants are filling their pots and are well established so they are more able to survive the move.

Partially cover and/or mist if necessary to lessen shock of removal from plastic bag
Two methods to lessen the shock are possible Either open the bags gradually, allowing more and more air flow, eventually cutting off the top of the bag. After a week or two of acclimatisation, pot them up, water and place in a shady frame. Alternatively, you may pot up the plants and acclimatise them after potting by giving them some temporary cover and misting if they show signs of wilting, again over a week or two. Whatever method you chose, some losses are likely, but many will survive.

Grow on and plant out once established

Potted fern V2

STEP 4  A well grown fern plant ready for planting out in the garden

  This information is also available as the BPS Spore sowing leaflet

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