Growing ferns from spores

Propagating Ferns: Growing Ferns From Spores And Division

Ferns are an ancient plant family over 300 million years old. There are over 12,000 species in almost all parts of the world. They provide airy foliage and texture for the home gardener, both as indoor and outdoor plants. Propagating ferns is easiest by division but they can also be grown from their spores. Growing ferns from spores, which takes many months up to a year, is an interesting process that provides an educational experience for the whole family.

What are Fern Spores?

In nature, these lovely plants reproduce through their spores. Fern spores are the tiny genetic bases for new plants. They are found contained in a casing, called sporangia, and grouped into bunches, called sori, on the underside of the leaves.

Spores look like little dots and may be harvested for fern spore propagation by the intrepid gardener. Timing and some skill are required when propagating ferns with these minute specks.

Care and Propagation of Ferns

Ferns are easy to grow and thrive in indirect light and high humidity. The soil doesn’t need to be very wet, but humidity is a crucial requirement for the plants.

Ferns don’t need to be fertilized in the garden but potted plants many benefit from once a month feedings with a liquid fertilizer diluted by half.

Prune off the fronds as they die back to make room for new growth and to improve appearance.

Gardeners can approach propagating ferns by division or from growing the spores:

Growing Ferns from Spores

Harvest spores when they are plump and slightly furry in appearance. Remove a healthy frond and put it in a plastic bag to dry out. When the leaf is dry, shake the bag to let the dry spores float down to the bottom.

Place the spores in a peat mixture in an unglazed pot. Set the pot in a saucer of water to allow the moisture to seep up through the entire mixture. Next, put the moistened pot into a plastic bag in a sunny, warm location of at least 65 F. (18 C.).

Fern spore propagation will take some time. Watch for a slime-like green coating on the surface of the peat. This is the beginning of the process and over many months you will begin to see small fronds appearing out of the slime.

How to Propagate a Fern with Division

A vigorous, healthy plant is more quickly reproduced from division. Any gardener that knows how to divide a perennial will recognize how to propagate a fern.

In very early spring, dig up or remove the plant from its pot. Cut it into sections between the rhizomes, leaving several sets of healthy leaves on each section. Repot in peat and make sure it is moderately moist while the new plant establishes.

Care and propagation of ferns couldn’t be simpler. This durable plant group will provide you with a lifetime of beauty and an unending supply of plants.

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.

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

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 – Patch 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
Ideally, patch out when the fern plants have several leaves and are clearly growing. Patching 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

STEPS 3 & 4 – Spore pan ready for patching out, and a tray of patchings 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

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

Germinating Ferns

SERIES 19 | Episode 08

Normally ferns are bought as ready grown plants and this often means paying a premium price – but there’s a cheaper way to grow ferns. It involves using their spore and it’s much more fun.

The place to look for fern spores is on the undersides of the fronds. They look like brown raised spotted areas. Break off the fronds (with the spores) and put them in an envelope. Hang it somewhere cool, dry and airy for two or three days until the spores are released into the envelope.

Next find a clean pot – one that’s been scrubbed clean in hot soapy water – and get some fresh propagating mix.

To give spores the best possible chance to grow, it’s best to pasteurise the soil surface – this removes any fungi or algae that might compete with the spores as they germinate. Find a piece of card and put it on the soil surface. Take some recently-boiled water and pour it over the card – it’s this process that pasteurises the soil.

Remove the card and wait until the soil has cooled down, then tap the spores onto the surface. (Remember this is a job for a still day because the spores are just like powder.) They take a few weeks to germinate and during this time it’s important to keep them evenly moist. A tip is to make a mini greenhouse from a plastic container, with a lid on it – a little cane could be used to hold the lid open for some ventilation.

It will take several months for the spores to be large enough to pot up and then you’re ready to start landscaping with your own ferns.

Sori containing spores on the underside of a fern frond.

Ferns certainly are very odd plants with a unique life cycle. Unlike most other plants we know, they bear neither flowers nor seeds. Instead, they mainly reproduce by spores.

Easier to Grow Than You’d Think

If you look on the Internet, you’ll find many sources of fern spores.

Few seed companies offer fern spores, probably because they’re convinced that growing ferns from spores is beyond the capacity of the average home gardener. But I beg to differ. I’ve grown all sorts of ferns from spores, starting when I was a child, and I’ve never found them all that difficult to grow.

What is true though is that growing ferns from spores takes a while, largely because the spore gives birth not to a fern, but to a preliminary life stage, the prothallus, and it is only after fecundation that a new fern is produced.

In the wild, it can take up to 4 or 5 years for a fern to reach its full size. However, patient gardeners will discover that it’s possible to grow most garden ferns to a useable size in only a year or two if you start them indoors, as they’ll be able to grow all year long rather than having to stop for a long winter’s rest, plus you’ll be offering them better conditions than in the wild (especially, not competition), so they are essentially able to put on 2- or 3-year’s growth in just one season. In most cases, if you sow fern spores in the spring, you’ll have a small fern ready to plant out the following spring.

The same goes for the tropical ferns grown as houseplants: most will be small but useable plants after only one year.

A Two-Phase Life Cycle

Ferns undergo a two-phase life cycle called the alternation of generations.

The life cycle of a typical fern.

Spores are produced on the fern’s fronds (frond is the term used for a fern leaf). Mostly they appear underneath the frond, but some species have separate “fertile fronds” (spore-bearing fronds) that are physically quite different from the others.

The sori under this frond almost look like scale insects… but scale insects never line up so symmetrically.

What you see under a typical frond are the sori (singular sorus), also called or spore cases, that contain the spores. They usually look like small bumps or lines, usually placed in a symmetrical pattern, and are often green at first, becoming brown or golden at maturity.

Inside the sori are clusters of sporangia (spore-producing cells).

The spores themselves, tiny to the point of being virtually invisible, are very light and usually carried by the wind. They are haploid (they contain half the number of chromosomes of an adult fern).

Harvesting Spores

If you can’t easily find commercial sources of fern spores (although, if you look on the Internet, you ought to be able to find a supplier), it’s easy enough to harvest spores from wild ferns or houseplant ferns. Here’s how:

Sterile Ferns

The vast majority of ferns produce fertile spores… but at least two commonly grown houseplant ferns do not. Both the Boston fern (Nephrolepis exaltata ‘Bostoniensis’) and its many variants, and also the crested elkhorn fern (Polypodium punctatum ‘Grandiceps’ produce deformed spores that aren’t viable, so there is no use harvesting and trying to sow them. Instead you can multiply sterile ferns from division or offsets.

Slip a mature frond bearing sori into a white envelope and in just a few days it will start to release spores.

When sori of a fern show their maturity by turning brown, cut a frond or part of a frond and slip it into a white envelope. After 2 or 3 days, you should see brown dust contrasting with the white paper inside the envelope: these are spores. You can sow them immediately (ferns that have green spores, especially, have a short “shelf life” and should be sown without delay) or store them until you are ready to sow them. Most can be stored for up to a year if you keep them cool and dry.

Sowing Spores

Sowing fern spores is not very different from the method used by most gardeners to start fine seeds indoors. There is one difference, though, and that is that fern seedlings are highly sensitive to contaminants (fungi, mold, moss, etc.). It is therefore wise to sterilize everything thoroughly before starting.

Sterilize the growing mix in a microwave oven.

To sterilize soil, mix it with water to dampen it thoroughly and place it in a plastic sandwich bag. Put it in the microwave oven without sealing the bag. Set the oven to maximum for 2 to 3 minutes. If no steam starts to condense on the inside of the bag, try a few minutes more. When the bag does steam up, take it out of the oven and seal it. Steam (which is actually the soil sterilization agent) will continue to form for several minutes. Let it cool to room temperature before you use the soil.

While you wait for your potting mix to cool down, sterilize all pots and tools by pouring boiling water over them.

When the potting mix reaches room temperature, spoon it into the pot you chose and smooth out the soil surface.

Broadcast sow the spores.

Broadcast the spores over the surface of the potting mix by holding the envelope so its top is pointing slightly downward, then gently tapping the envelope as you move it back and forth. That should spread the spores out nicely. Don’t cover them with soil: they need light to germinate.

Now place the pot inside a clear plastic bag (it will serve as a mini-greenhouse) and seal it shut. Move it to a warm, modestly well-lit spot, but with no direct sun, perhaps under a fluorescent lamp.

After a few weeks or months, small green growths, generally translucent, heart-shaped and looking a lot like liverworts or mosses, will form on the surface of the potting mix. They’re called prothalli (singular prothallus or prothallium) and are the sexual phase of the fern’s life cycle. They too are haploid, with half the number of chromosomes of an adult fern.

Fern Sex (readers 10 years and younger should be accompanied by an adult!)

The prothallus often looks like a heart-shaped, translucent liverwort.

Each prothallus produces many haploid male gametes (sperm) and one haploid female gamete (egg). (Okay, a few ferns produce a unisexual prothallus, but that doesn’t change our story much). The prothallus’ male gametes are mobile, but need the presence of a thin film of water to swim to the female gamete of another prothallus, hence the importance of maintaining high humidity inside the bag. When the haploid male gamete finds a haploid female gamete, fecundation takes place, forming a diploid cell, that is, one with a full complement of chromosomes. What was half is now whole and the alternation of generations is complete!

(Possibly there is a small moment of ecstasy as the two cells join together, but I’m not sure that’s been studied.)

The first frond appearing from a bud on the prothallus. Soon there will be many fronds.

After another few weeks, a small diploid sporeling (baby fern) will become visible, first with just one small frond, then another and larger one, then another, etc. The prothallus will soon fade away, leaving you with a small but independent fern!

When the plant reaches this stage, it’s time to acclimate it to outside growing conditions. Do so by opening the plastic bag bit by bit over a period of a week or so the young fern can adapt to the lower humidity outside. Then you can remove the bag entirely.

From Baby to Big

From this point on, you’ll be maintaining your baby ferns (yes, you’re much more likely to have dozens than just one!) like any other seedling.

Offer them good light, decent air humidity, regular moisture (most ferns don’t like to dry out), a bit of fertilizer from time to time and, when the ferns start to crowd together, transplant them into individual pots. Their growth will accelerate considerably at this point and soon they’ll be big enough to plant outdoors (hardy ferns) or to grow as houseplants (tropical ferns).

There you go: growing ferns from spores is not that different from growing plants from seed. It’s even a fascinating project any gardener can handle. Pencil it into your busy gardening schedule for this season!

If you’re not in the know about ferns, then you’re missing out. They’re actually quite an interesting plant. They’re one of the oldest living organisms on the face of the Earth. Botanists have estimated that the fern is over 350 million years old. They’ve been around a while. They’ve even managed to develop twelve thousand different types of ferns found all over the world in several different types of settings.

So somehow the excellence of ferns has escaped you throughout the span of your life, but we’re here to help you overcome this lack of knowledge. Here is a quick summary of a few of the most interesting facts about the glorious fern.

Ferns reproduce using spores.

Ferns don’t reproduce like other “flowering” plants do. They reproduce asexually, meaning they don’t need pollen like most other plants. Ferns actually have spores, kind of like mushrooms. If you look underneath their leaves (or fronds), you’ll see a plethora of little spots. Those are the little sacks that protect the plant’s spores.

Ferns are fickle in their reproduction. Their spores have to have just the right type of setting for growth to occur. They need thoroughly moist and rich soil to successfully root themselves properly. They like to grow underneath a thick canopy, which is why the fern thrives in the rainforest environment.

Ferns are great filters for the air.

Just like most plants, they take in carbon dioxide from the air and release oxygen. They do a lot more than that, though. NASA scientists have discovered that ferns are capable of ridding the air around us of formaldehyde, xylene, and toluene. These pollutants have been known to be cancer causing agents when inhaled by humans.

Identify the different parts of the fern.

It’s already been mentioned that the leaves or branches of a fern are called the frond. Underneath the fronds of the plants, you will find a bunch of raised, speckled dots. These are called sori. They are clumps of sporangia or spores. You won’t always find these spots on the underside of the fern’s frond, but if you do, this means that this part of the fern is fertile.

Not all ferns look the same or live in one specific area of the globe. Ferns actually can be found on every continent, except for Antarctica. The climate is a bit too extreme for anything to grow in Antarctica.

Ferns come in all different shapes, sizes, and colors.

If you’re like most people, then you just assume that ferns are green, but they’re not always green. They all grow in similar environments, but some species of the plant actually grow in bright vibrant colors. Sometimes their new growth comes in oranges, reds, and yellows. One species, the Japanese Painted Fern, grows in with beautiful purplish, red stems and leaves. They form a wonderfully natural contrast with its silvery leaves.

The size of the fern also produces a sense of variety. Some ferns stay low to the ground and only grow a few inches high. Others can grow anywhere from fifteen to thirty feet high.

Propagation

Growing Ferns From Spore courtesy of Sue Olsen

Ferns are reproduced from spores that are gathered in clusters called sori, which are usually on the underside of the fronds. The spores can be yellow, green, brown, or black. The sori are sometimes covered with a membrane called an indusium, which will lift up when the spores are ripe. In the Pacific Northwest, spores ripen from late May through October and will waft off like fine dust.

To gather the spores, pick a frond or portion of a frond and place it between two sheets of white paper. If ripe, the spores should drop within 24 hours and will leave a pattern on the paper. Frequently, chaff will drop as well, and this must be removed before sowing. To get rid of the chaff, tilt the paper slightly and tap gently. The chaff will fall away while the spores remain behind. (Practice with a non-important fern first!!)

The spores are then ready to be sown. I use a clear plastic container with a sterilized earthworm compost mix, but there are many other options. The spores are dusted on the top of the mix and the lid put on the container, which is then placed under cool white fluorescent lights that are turned on for 14 hours a day. The spores must be out of direct sunlight.

In time perhaps as soon as several weeks a thin, green haze will form on the mix. This will grow into a carpet of prothallia, which are small, green, heart-shaped structures and contain the sperm and the egg. When the prothallia are approximately ¼ inch, they should be lightly misted to hasten fertilization. If no little sporelings appear in several weeks, mist again.

I then move small clumps of prothallia/sporelings to a mix of peat, vermiculite, and compost potting soil in a covered mini-greenhouse. This is also placed under fluorescent lighting where the sporelings are grown on until they are about one inch tall. At that time I harden them off by gradually lifting the lid of the greenhouse. They are then transplanted into pots, and finally moved out of doors when they are four to six inches tall depending, of course, on the season.

Prothalli with the first true frond coming up on the right.

Removing Spores From Leather Leaf Fern

Ask the Expert: I have problem with the Spores on Leather Leaf .
The spores are popping and leaving a mess in fresh flower arrangement’s, What can I do to stop this, The wholesaler says its normal for this time of year but I cant send out flowers with fern spores leaving a mess everywhere. Vonda

Flower Shop Network Plant Expert Reply:
The wholesaler is correct about this being the time of year (June-July) that ferns release their spores. However, that knowledge doesn’t solve your problem. You may need to remove the spores just like you have to remove pollen in lilies.

I personally haven’t removed ferns spores before, but I researched spore removal. When fern growers need spores to create new plants, they take the fronds with ripe sori (the part of the leaf containing the spores) and fold a piece of paper over them. In a day or two, the spores drop on to the paper.

In the flower shop, I would recommend wiping the back side of the frond with a soft paper towel. Any ripe spores should detach from the leaf. If the spores won’t release, gently taps the frond.

Hopefully, this will be a solution to your problem. Please let us know if this solves your problem.

If you’re one of those people who hates waiting for seeds to germinate, then raising ferns from spores is definitely not for you. The lengthy process of spores transforming from prothallium to baby ferns can take anywhere from 6 to 18 months. Fortunately for impatient gardeners, several ferns can be propagated from rhizome cuttings or better yet – ready to root, tiny plants. One such species is Polystichum setiferum or Soft Shield Fern. There are many different cultivars or forms of this lovely semi-evergreen plant, many of which (including ‘Proliferum’ and ‘Herrenhausen’) are noted for this particular trait of developing baby ferns along the midribs of mature fronds. The best examples of this spontaneous reproduction come from the lower fronds, which have been sheltered from the elements and kept nearly constantly moist. Propagation is really quite easy – simply cut the stems (with the baby ferns growing out of them) into 1-2″ long pieces, prune the side leaflets to half their original length and pin this segment (using a piece of wire) to the moist surface of a sterile growing mix. You can do this in a flat or 4″ pot, but you will need to cover it with a plastic dome (or sheet) for light and humidity. I kept my cuttings in an openly shaded area, where they rooted in about 6 weeks.

Leave a Reply

Your email address will not be published. Required fields are marked *