Bracken Fern - our deadly enemy (or is it?)

Bracken fern

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Bracken or Fern brake (Pteridium aquilinum and other Pteridium species) is known to have carcinogenic contents, also vitamin inhibiting components that cause other symptoms, including death, in animals that graze on it. It can spread rapidly from rhizomes, and in the right climate, also widely by fine seeds or spores. However, the shoots are widely used as a vegetable in Eastern Asia, a starch is extracted from the root that makes noodles and a Japanese sweet formerly eaten by Royalty, and it also makes a superb mulch and compost for the garden (see this summary document for example). How can all these things be reconciled and understood so that we can use it safely?

I’m interested in bracken because it grows widely here in the UK. In fact it is a persistent weed for much of the world’s landmass, excluding only extremes of temperature and water logged soil; it won’t grow in marshes. I’ve been researching it more recently and believe that it is possible to use it safely if you take some precautions. I’m not an expert, just an interested amateur, so if you have heard differently please comment below and share your information.

Bracken taking over sheep grazing

I’m not going to go into the problems caused to livestock eating bracken. If someone who is interested in livestock management wants to add more information that would be great. I understand that normally they will avoid it unless there is nothing else for them to eat. This has the effect of the bracken gradually taking over meadows unless action is taken to reduce it, although trampling on the emerging crosiers can reduce the growth somewhat. Because bracken has also anti-insect properties, there is little that will normally reduce the bracken itself.
Other uses of bracken include animal bedding, insulative underthatch for roofs, various medicinal uses, a dyestuff and fibre for basket weaving, See also Bracken.

Bracken fern shoots in spring

The main carcinogen and allelopathic component in bracken is ptaquiloside (PTA). The amount of PTA in bracken varies with the part of the plant and the time of the year. There also appear to be some strains of bracken in the USA and New Zealand that are entirely PTA free (ref.)  although you would presumably need to have a laboratory test your bracken to be sure of this. In general there is most PTA in the growing shoots in spring, less in the mature stems and the least in the roots.  The PTA is easily destroyed by the action of heat, and water. Blanching fronds in slightly alkaline boiling water for just 2 minutes was found to reduce the PTA by 65%, boiling for 20 minutes in water reduces it by 99%, reducing it to a level considered safe. Good practice appears to be to wash the fresh fronds, rubbing off the tips and stem hairs, strain, then boil 5 mins in fresh water, dry (2 days in sun) steam ½ hour, dry again (one day in sun). The shoots can then be stored for whenever you want to eat them. When it comes to cooking them rehydrate with boiling water, leave to soak overnight, then stir fry or cook into stews.
To be honest I’m more taken with the idea of extracting starch from the rhizomes. They contain about 65% starch by dry weight, although much of the fresh weight is water so the extraction rate is more like 5% from fresh rhizomes. However the amount of bracken root has been estimated to be up to 5kg dry weight per m2 in the UK (ref.). The starch can be extracted and stored to be used as a cooking ingredient. Also apparently Maoris and other Pacific peoples, as well as North American first peoples, pit roasted and ate the rhizomes as a vegetable, although online reports suggest that this is not palatable to modern tastes. The roots were also dried by the Maoris for ease of carrying during trips.
From this paper “products, mainly those based on rhizomes, were found to contain no PTA …... Rhizomes and rhizome-based products could be considered safe concerning PTA toxicity and when prepared from rhizomes collected in winter, which seems to be the practice in China”. There is more PTA in the roots in the autumn, as the nutrients from the leaves are being stored, rather than in spring when the new shoots are growing, but generally the amount of PTA is less than half that of the shoots (ref.) . Again much of the PTA will be leached into the water whilst extracting the starch, or destroyed during the cooking process.
To extract the starch the roots need to be cleaned of mud by scrubbing and rinsing with water, the roots are then crushed or minced, the starch is then rinsed out into water and the fibrous solids filtered off. The water is then left to settle overnight and the water poured off leaving the starch. This may need cleaning by rinsing with clean water and filtering 2 or 3 times. The starch can then be dried and used for cooking. This video is one I found that shows the full process: .
Alternately, a thin batter can be made from the starch and steamed to make pancakes which are then dried, then rehydrated and sliced to make noodles (more videos showing the process: https://www.youtube.com/watch?v=miMZwMiDSN4, https://www.youtube.com/watch?v=oR7SvmM7c-Y). The worst bit of processing seems to be the cleaning of the roots.
The starch is apparently somewhat like potato flour in character and is used in Japan to made warubi mochi, a kind of jelly confectionery coated in soybean powder. Because of the expense of pure bracken starch, which is available commercially from China and Japan ( example and another example) for about £100/kg these are normally actually made from blends of other starches.

Bracken competes with other plants in various ways. First there is the canopy it forms, which shades out other plants. Bracken can grow up to 6 foot tall in the UK. In addition the PTA washing off the top growth inhibits seed germination (ref.) although it is short lived in the soil, quickly being degraded by microbial action (ref.). So mulching with fresh bracken will inhibit weed seeds from germinating, but not affect established plants, and will break down to form good compost in time: my blog post on bracken compost.
There is a possibility that PTA can leach into drinking water supplies in high rainfall areas, and also be present in milk of cows that include it in their diet, which could theoretically be of concern in some areas (ref.). Spores are released from mature plants in hot weather, but are quickly washed out of the air by rain.

I think we can make a resource out of a nuisance, however I still wouldn’t suggest introducing it onto your land if it doesn’t grow there currently. Chances are it won’t be far away anyway and the landowners there will be only to happy for someone to take some away.


I apologise for the length of this post, I just thought people might like to have the information I have gathered in one place.

Having enjoyed gosari namul/fernbrake/ bracken fern in Korean meals many times, I had no idea I was flirting with danger!

This was very interesting from the perspective of having eaten it without knowing much about the big picture of the plant. I had only really heard of it otherwise for contaminated soil remediation.

I am guessing as a pioneer plant it produces plenty of organic matter that drops to the ground.
I hope that then builds the soil quality.
I have never thought of eating it though!

Every spring, I see people in foraging/gardening groups on Facebook talking about which ferns are edible and the dangers of bracken. I keep this link queued up to paste into all those discussions. Some of my favorite Sichuanese pickles have bracken in them.

Christopher Weeks wrote:Every spring, I see people in foraging/gardening groups on Facebook talking about which ferns are edible and the dangers of bracken. I keep this link queued up to paste into all those discussions. Some of my favorite Sichuanese pickles have bracken in them.

Yes that link was one I found in my searches. I did actually try a (singular!) bracken fern crosier this spring. Being the first time, I boiled, soaked and recooked it three times, which I think was overdoing it in the end! It turned out quite tasteless. Maybe I've been brainwashed into being too scared of it still.

I'm still trying to work out how to harvest the rhizomes though. I'm thinking getting paid twice - by the land owner for 'clearing' the bracken, and then £100/kg for bracken root flour! Alternatively it could be a useful starch source in hard times. I'm a bit surprised there doesn't seem to be more of a history in the UK of using it as famine food, given how ubiquitous it is. I could only find a few references to medicinal uses of the root.

Bracken Fern does have some redeeming qualities.

Just one is the remediation of heavy metals:

https://academicjournals.org/journal/AJEST/article-full-text-pdf/7CE1F3765071

Growing potatoes by chop & drop bracken:

   

Part 2: Harvest four months later  

It looks like they got a reasonable crop - so conclusion may be that potatoes don't mind whatever allelopathic compounds the bracken fern gives out - good info thanks!

I haven't done any further experimentation this year, but did stumble accross this useful article on ethnobotanical uses for bracken: https://historicengland.org.uk/content/docs/advice/bracken-the-palaeoethnobotany-of-pteridium-aquilinum/

Cut green bracken gives off cyanide gas so was used for packing and displaying soft fruit and fish until relatively recently.

They can also be used to help store root vegeatbles and potatoes in a 'clamp' over winter:

A thick layer of bracken about 0.75m wide was laid down and the potatoes, as clean and dry as possible, were put on top, tightly packed together. A layer of bracken was placed over the potatoes followed by another layer of potatoes. The whole was finished off by a15cm layer of bracken. This was then covered with a thick layer (30cm or more) of earth dug from the sides of the clamp or with turves or peat

Used as building materials (in 'wattle and daub') and also for thatching, fuel and bedding materials.

There is a suggestion it was used in textile processing - although not suggested in the text I wonder whether dyeing might be a possibliity? In the table it suggests green and brown colours can be obtained.

Also bracken spores gathered on midsummer's eve makes you invisible (allegedly)

This really was a fascinating read, I had no idea about Bracken aside from it being a nuisance at times when moving through the woods doing some photography. It really is a big problem here in the UK now, and have certainly noticed an upsurge in density through woodlands in general.

Hey there, my family and I routinely eat Bracken fern shoots in the spring. Should we eat them from Forest fire areas vs from healthier ecologies only is the thing up for debate. And that’s just because it’s morel season. And we use them as a gauge if morels are coming yet (if the eagle’s claw has opened, it’s morel time). And I’ve made coil baskets with them. Good for restoring areas. Keeps weeds out.

Elizabeth Cramer wrote: And I’ve made coil baskets with them.

Hi Elizabeth - I don't think I found making baskets as a use for bracken...Do you use them green? I find the stems rather brittle once they are mature. What do you use the baskets for? How durable do you find them?

Nancy Reading wrote:

Elizabeth Cramer wrote: And I’ve made coil baskets with them.

Hi Elizabeth - I don't think I found making baskets as a use for bracken...Do you use them green? I find the stems rather brittle once they are mature. What do you use the baskets for? How durable do you find them?

Hey Nancy, thank you for your question. I wanted to offer some validity to what the post was about, how it said that it could be used for thatching. Yes, it can be used for all types of textile things, including baskets. So, I am not somebody who prepares when I make my basket. I’m somebody who walks around and grabs things in real time. I tend to use the tops and not the stems because I like the way the fronds stick out. The better ones are ones where they have gone through an entire winter. I’m guessing the brittle part that you mentioned probably gets retted away in the decay of winter . The green does not work. The barely dead does not work.

Another material that is quite similar (but stronger) in how it functions as a basket material is sword fern if you happen to have any near you.

How I use the baskets is variable, and I have done each of what I am about to say. The basket ends up being very floppy and malleable. And so gorgeous. They make great inserts for metal hanging planters and you can plant right in them. The other use is as a seed starting ‘pot’. I’m guessing they taste bitter because creatures seem to be avoiding of them but plants don’t seem to mind them at all. I have one little hand size bracken basket that has made it inside for two years now as a planter for an orchid. But finally, I use them as decorative add-ons for their color and their fronds. They do not make the best exclusive material for baskets. But they are gorgeous bonus material.

I had heard that Bracken helps made Phosphorus (P) more available for plants.
This article - https://academic.oup.com/jpe/article/15/4/783/6376063 - supports what I heard.

What I can't remember for sure from my original, long lost source, is whether it said that once the Bracken had rebalanced and made available P in the soil, it would tend to decline or other plants would be more able to out-compete it?

Certainly, if I had animals at risk of eating bracken out of desperation, I would need to do something about it. But that may just mean that it's warning me that the soil in an area is struggling, so rather than being an "enemy", maybe it's a "messenger"?

Being that I forage fiddleheads most springtimes, but I flash boil then bake (liver cancer from fluke being a concern, also salmonella.) usually I make a soufflé.

I know when it's fiddlehead time because the trilliums blossom, the black fly are chronic, the wild leeks are poking up, and the angelic dragon flies have yet to arrive.

I freeze all my fiddleheads until the ferns have matured then go back to my collection site and ensure there are only edible ferns in the spot where I collected. Then I go ahead and start dipping into my frozen fern heads, a couple weeks later or so at my convenience.

I had never heard of eating the shoots, but where I live ostrich ferns are dominant and there aren't many spots where bracken grows -- probably too cold, too wet, perhaps too acidic. (Moraine, poor soil, and mixed forest Quebec)
Edit: reading below, NOT because it's wet, cold, acidic, perhaps just providence,!

Brackens can tolerate acidic and poor soil. One place I remember seeing lots of brackens is a subtropical secondary forest with high soil iron oxides. The red clay mountain has very limited diversity, dominated by pines and brackens.

Yes bracken tolerates a very wide range of soil conditions (which makes them so successful) The one thing I believe they can't take is permanently waterlogged soil. Wet and draining is OK, or they wouldn't take ovet the sheep paddocks round here so well. I suspect if it is too hot and dry they won't like it either, and they are happy in a lot of shade in hotter climates than mine. Even here they grow pretty happily under my spruce trees.

People here use pigs to clear bracken. I wonder if the pigs are getting some food from the roots or rhizomes.

We had a lot of trouble here with goats and bracken our first few years here. Most adult goats can nibble a bit here and there without problems (so long as there is other food there for them), but our baby goats used to have a very low tolerance to it. Over the years the goats that we've bred either have a higher tolerance for bracken when young, or have inherited some instincts to stay away from it, I'm not sure which.

Kate Downham wrote:People here use pigs to clear bracken. I wonder if the pigs are getting some food from the roots or rhizomes.

They do the same thing here - you can see the patches where the pigs were penned for a few years, then the bracken will move back in. I suppose even pigs will leave scrappy bits that regrow. There is quite a bit of starch in the rhizomes, so there is probably quite a bit of nutrition for the pigs.

As regards goats, I don't know. I gather that eating the foliage causes mal absorption of vitamins (vitamin A perhaps?) which can cause quite severe sypmtoms. Most animals will know, or learn, to avoid the bracken f they have a choice of foodstuff to browse. It would be interesting if others have knowledge there to share.