Ferns can be propagated in two main ways: by dividing an established plant or by growing new plants from spores. For most home gardeners, division is the quicker and more predictable method when the fern has a creeping or branching rhizome, several growing points or multiple crowns. Spore propagation is slower, but it allows you to raise ferns that cannot be divided and can produce many plants from a single fertile frond.

The two methods are not interchangeable. A division is a piece of the parent plant and keeps the same characteristics. Spores are part of the fern's sexual life cycle, so the resulting plants can differ from the parent. That distinction matters particularly with named cultivars and hybrids.

If you are new to fern growing, start with division where the plant's growth habit allows it. Try spores when you want to understand the full fern life cycle, raise larger numbers or propagate a fern that does not naturally make suitable divisions. For broader guidance on siting and caring for established plants, see our complete guide to growing ferns in Ireland.

1. Choose the right propagation method for the fern

Before lifting a plant or collecting spores, look at how the fern grows.

Division suits ferns with more than one viable growing point

Division works best on ferns that spread through creeping or branching rhizomes, form several crowns, or produce rooted offsets away from the parent. The important point is that every new division must contain enough living plant material to continue growing, especially an active growing tip or complete crown and a useful amount of root.

Long-creeping ferns can often be separated along the rhizome. Clump-forming ferns with several branching growing points can be split into substantial sections. Stoloniferous ferns such as ostrich fern, Matteuccia struthiopteris, may produce young plants at some distance from the parent that can be lifted and replanted individually.

Spores suit ferns that cannot be divided

Some ferns have a single, unbranched growing point and provide no sensible place to divide the plant. These generally need to be raised from spores unless they have another specialised vegetative method such as buds or bulbils.

Spore propagation is also useful when you want more plants than division could reasonably provide. A fertile fern can produce a very large number of spores, but the trade-off is time and the need to keep the young stages clean, humid and consistently moist.

2. When should you divide a fern?

Choose a time when the divided plant can re-establish without being asked to support a full canopy of soft new fronds at the same time.

• Early spring: divide before the new fronds have fully expanded. This gives the plant a growing season in which to rebuild its roots.
• Autumn: division can also work where winters are mild, particularly after active top growth has slowed.
• Avoid stressful conditions: do not divide during hot, dry weather or when the plant is already struggling with drought, damaged roots or another serious problem.

In cooler or more exposed Irish gardens, spring is the safer general choice because the new division has more mild growing weather ahead of it. In sheltered gardens with mild winters, autumn division can also be practical.

3. How to divide a fern step by step

Step 1: Find the growing points

Look at the base of the plant and identify where new fronds arise. On a creeping rhizome, this means finding active tips. On a multi-crowned fern, look for complete crowns rather than cutting blindly through the centre of a rosette.

Do not reduce a fern to tiny fragments simply to maximise the number of plants. Larger divisions generally have a better reserve of roots and stored energy and establish more reliably.

Step 2: Lift enough of the root system

Use a fork or trowel to loosen the soil around the section you want to remove. Preserve as many fine roots as reasonably possible. Fern roots are often fibrous and close to the surface, so rough digging can remove the very roots the division needs for recovery.

For a large clump, it may be easier to lift the whole plant and divide it where you can see the crowns and rhizomes clearly. For a spreading fern, you may only need to lift an outer section or a rooted offset.

Step 3: Make a clean division

Use a clean, sharp knife, spade or pair of garden forks, depending on the size of the plant. Separate the fern at a natural branch, joint or clear division between crowns where possible.

Each piece should contain:

• at least one healthy growing point or complete crown;
• a useful portion of rhizome where the species has one;
• healthy roots;
• enough frond or bud material to support continued growth without leaving an excessive leafy top.

If the plant has several crowns, take whole crowns with roots attached. Cutting a crown in half may leave a weak, misshapen division and can damage the growing point.

Step 4: Remove damaged material

Trim broken or dead fronds and damaged roots. If the division has lost a substantial amount of root, reducing some of the older foliage can lower water loss while the root system re-establishes. Do not strip away healthy new growth unnecessarily.

Step 5: Replant promptly

Do not leave divisions sitting with exposed roots. Replant them at approximately the same depth at which they were growing before, firm the soil gently around the roots and water thoroughly to settle the root zone.

A newly divided fern benefits from a sheltered, shaded position and consistently moist soil while it establishes. It should be moist, not permanently saturated. If you are moving the new plant to a different part of the garden, our guide to planting ferns covers position, planting depth and establishment in more detail.

4. How to care for a newly divided fern

The first priority is to balance the remaining foliage with the reduced root system. A division may wilt even when the parent plant was previously well established because it can no longer draw water from the same volume of soil.

• Keep the soil evenly moist while new roots develop.
• Protect the plant from strong sun and drying wind during early recovery.
• Do not keep adding water to already saturated soil. Poor aeration around damaged roots can encourage further decline.
• Delay heavy feeding. New divisions need roots and stable moisture more than a strong flush of soft growth.
• Expect some older fronds to deteriorate after division, especially if root loss was unavoidable.

Successful establishment is shown by firm new growth and roots beginning to occupy the surrounding soil. Once the plant is growing normally, return to the usual care for that species.

5. Fern spores are not seeds

Spore propagation makes more sense once you understand why it is different from sowing flower or vegetable seed.

The familiar leafy fern is the sporophyte. When mature, it produces spores inside tiny structures called sporangia, which are commonly grouped into visible patches or lines called sori on the underside of fertile fronds.

A spore does not grow directly into a miniature version of the adult fern. It first develops into a tiny, thin green plant called a gametophyte or prothallus. This stage produces the fern's reproductive cells. A film of water allows sperm to reach an egg, and after fertilisation a new leafy sporophyte begins to grow from the prothallus.

This is why spore propagation needs persistent surface moisture and humidity. The moisture is not simply there to stop the compost drying out. It is part of the reproductive process itself.

6. How to collect ripe fern spores

Do not collect simply because you can see brown marks under a frond. Sori change as they mature, and collecting too early may give you immature material while collecting too late may mean the spores have already been released.

Look for mature fertile fronds

Depending on the fern, ripe sori may become darker and any covering over them may begin to lift as the sporangia mature. The exact colour and arrangement vary between genera, so the most useful test is whether the frond actually releases fine spore material.

Use the paper test

1. Cut a small fertile section of frond that appears mature.
2. Make sure it is dry on the surface.
3. Place it between or over a clean sheet of plain paper.
4. Leave it undisturbed while the sporangia release their contents.
5. Remove the frond and separate the fine spores from larger pieces of chaff as carefully as you can.

Ripe spores can form a fine dust-like pattern on the paper. Cleanliness matters because fragments of old frond and other debris can carry algae, moulds or fungi into the sowing container.

Fresh spores are generally the best starting point. Some green-spored ferns have particularly short-lived spores and need to be sown promptly.

7. Prepare a clean container and growing medium

The most common failure in home spore propagation is not that the fern biology is too complicated. It is that algae, moss, mould or other contaminants take over the moist surface before the fern develops.

Use a small clean container that can be covered with a clear lid, glass or transparent plastic. It should be deep enough to hold a shallow layer of fine growing medium with room above for the young plants.

A fine, moisture-retentive but aerated medium is easier for tiny prothalli to colonise than a coarse mix. Before sowing, reduce contamination by treating the medium. A practical home method described in fern-growing references is to pour boiling water carefully through the prepared medium, then keep it covered while it cools completely.

Do not sow until the container and medium are cool. After treatment, avoid touching the surface unnecessarily.

8. How to sow fern spores

1. Moisten the medium first. It should be evenly damp but not waterlogged.
2. Sow very thinly. Spores are tiny, so a small amount can cover a surprising area. Dense sowing creates overcrowded prothalli and makes later separation harder.
3. Leave the spores on the surface. Do not bury them under compost.
4. Cover the container. A clear lid maintains humidity and greatly reduces the need for repeated watering.
5. Give bright indirect light. Keep the culture away from direct sun, which can overheat a closed container and dry or damage the developing growth.
6. Keep conditions steady. Avoid repeatedly opening the container to check progress.

Once the spores are sown, patience becomes part of the method. Germination can take weeks, and some species are much slower than others.

9. What happens after the spores germinate?

First you see a green film

The first obvious sign is often a fine green haze on the surface. This develops into a carpet of tiny prothalli. At this stage you still do not have recognisable fern fronds.

Moisture allows fertilisation

As the prothalli mature, a fine film of water allows fertilisation to take place. In a covered culture, humidity is normally high, but if the surface is no longer adequately moist, a very light mist can help. Avoid flooding the container.

Young sporophytes appear

After fertilisation, tiny leafy ferns begin to emerge among the prothalli. The earliest fronds may not look like the adult fern. As the young sporophyte grows, later fronds gradually develop the characteristic form of the species.

Separate them gradually

When young ferns are large enough to handle, move small groups rather than trying to tease apart every microscopic plant. Pot them into a fine, well-drained fern mix and keep humidity high while they recover from transplanting.

As they become established, harden them off slowly by increasing ventilation over time. Moving young ferns abruptly from a sealed humid container into ordinary room or outdoor air can make them wilt quickly.

10. How long does it take to grow ferns from spores?

There is no single timetable. A green haze may appear within several weeks under suitable conditions, but producing a sturdy young fern takes much longer. Depending on the species and conditions, the process from sowing to a useful young plant can take many months, and slower ferns may need a year or two or more before they are robust enough for normal garden handling.

This is the main practical difference between the methods. Division starts with a plant that already has roots, rhizome and a growing point. Spore propagation starts at the beginning of the fern life cycle.

11. Common problems when propagating ferns from spores

Nothing germinates

The spores may have been immature, already shed, too old, or unsuited to the conditions provided. Try again with fresh, visibly fertile material and keep the culture consistently moist with indirect light.

Green slime or moss takes over

Contamination usually gains an advantage when the sowing medium, container or collected material carries unwanted organisms. Start with cleaner spores and a freshly treated medium rather than trying to rescue a culture that has been completely overwhelmed.

The prothalli grow but no young ferns appear

Overcrowding can interfere with successful development, and the reproductive stage also depends on adequate surface moisture. Thin an excessively dense culture into a second clean container and maintain a moist, humid environment.

Young ferns collapse after opening the container

This usually points to a sudden drop in humidity. Harden young ferns gradually by opening the lid a little more over several stages rather than removing it permanently in one step.

Young plants rot after potting

A pot that is too large or a mix that stays saturated can leave the small root system surrounded by wet, poorly aerated compost. Use modest pot sizes, a fine but free-draining mix and careful watering.

12. Will a fern grown from spores be identical to its parent?

Not necessarily. Division is vegetative propagation, so the new plant is a clone of the piece you removed. Spore propagation is normally sexual, which means the offspring can vary genetically.

This is especially important with named cultivars. Some cultivars may reproduce their distinctive features from spores, but others do not. A seedling-like sporeling may resemble the parent without being an exact copy. Many fern hybrids are also sterile or produce poor spores, so division or another vegetative method may be the only reliable way to preserve them.

If your aim is to increase one particular garden cultivar exactly as it grows now, divide it where its structure allows. If your aim is to raise species ferns, produce larger numbers or simply explore fern propagation, spores are the more interesting route.

Frequently asked questions about propagating ferns

Can I grow a fern from a normal frond cutting?

Usually no. An ordinary piece of fern frond does not behave like a stem cutting from many flowering plants. Some specialised ferns produce buds, bulbils or plantlets on their fronds, and those can be rooted, but that is a particular feature of those ferns rather than a general cutting method.

Can every fern be divided?

No. Division depends on having more than one viable growing point, a branching or creeping rhizome, multiple crowns or removable offsets. A fern with one unbranched crown may be badly damaged or killed if that single growing point is cut apart.

Should I divide a fern into as many pieces as possible?

No. A larger division with healthy roots and a complete growing point generally has a better chance of establishing than a collection of tiny fragments. Aim for strong new plants rather than the maximum possible number.

Do fern spores need to be covered with compost?

No. Sow them thinly on the surface of the prepared medium. The container is then covered to maintain humidity, but the spores themselves are not buried.

Why is cleanliness so important when sowing spores?

The warm, damp conditions that suit fern gametophytes also suit algae, mosses, moulds and other organisms. Reducing contamination at the start gives the slow-growing fern stages a much better chance to establish.

Division or spores: which should you choose?

Use division when the fern has a suitable rhizome, several crowns or rooted offsets and you want another plant with the same characteristics. Use spores when division is not possible, when you want to raise many plants, or when you want to grow a fern through its full reproductive cycle.

For the average garden fern, division is the practical first choice. Spore propagation requires more patience, but once the sequence from spore to prothallus to young sporophyte makes sense, it becomes a manageable home-gardening project rather than a mysterious process.