Common polypody
Quick Facts
- What it is: The sweet-tasting underground stem of a small Northern European fern, used in Scandinavian folk medicine for coughs and sluggish bowels.
- Main uses: Chesty cough and thick mucus, Mild constipation, Poor appetite, Sore throat
- Active ingredients: Osladin (a sweet steroidal saponin), Polypodosaponin, Ecdysteroids such as 20-hydroxyecdysone, Phloroglucinol compounds, Tannins and mucilage
- Forms: Dried cut rhizome for tea or decoction, Tincture, Powdered root in capsules, Ingredient in traditional cough syrups
- Time to effect: Laxative effect, if any, within a day; other uses have no proven timeline.
- Side effects: Mostly loose stools, cramps and nausea; rare fern allergy.
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What is Common polypody?
Common polypody is a small evergreen fern of Northern Europe. It grows on rocks, stone walls, mossy banks and old tree trunks. The part used is the rhizome, the creeping underground stem.
The fresh rhizome tastes sweet first, then bitter. In Scandinavia it was taken mainly for coughs, for sluggish bowels and as a bitter tonic for poor appetite. Children also chewed bits of the root as a wild sweet.
Here is the honest verdict. There are no good human trials on this fern. Long folk use tells you people trusted it; it is not proof that it works, and it is not proof that it is safe.
One warning about names. Do not confuse it with Polypodium leucotomos, a different fern sold for sun-sensitive skin. That species has its own human studies, and they do not apply to common polypody.
Treat it as a mild traditional herb with thin evidence. The main practical risk is a loose, crampy gut, especially if you take a lot or take it for weeks.
How does Common polypody work?
No study has shown in people how common polypody works, or that it works at all.
The sweet taste comes from osladin, a steroidal saponin. Saponins in general can mildly irritate the gut lining. That is the usual textbook explanation for a looser stool and for a thinner, easier-to-cough mucus.
That idea comes from saponin chemistry as a group, not from trials of this fern. Whether it happens in your chest or your gut is not established.
Bitter compounds in the root may prompt more saliva and digestive juice when you taste them. This bitter reflex is well known in general. It has not been measured for this plant.
Test-tube work on polypody extracts has reported antioxidant activity. A result in a dish says nothing about what happens after you drink a tea.
The root also holds ecdysteroids, which act as hormones in insects. In mammals they have been studied mostly in animals and cells, with unclear results.
What forms does Common polypody come in?
Most often you will find the dried, cut rhizome, sold for tea or a simmered decoction. It is a niche herb rather than a shelf staple.
Other forms turn up now and then. Some makers sell an alcohol tincture. Others sell the powdered root in capsules.
It also appears as a minor ingredient in a few traditional cough syrups and bitter blends.
The fresh root was chewed in the past. Fresh plant material is rarely sold today.
Labels can be vague about species. Check that it says Polypodium vulgare, not Polypodium leucotomos.
Never gather ferns yourself unless you can name them with certainty. Bracken, a common look-alike fern, contains a known cancer-causing compound.
Where it comes from:
Scandinavian country people used polypody rhizome for centuries. Norwegian sisselrot, Swedish stensöta and Finnish kallioimarre all name the same fern.
Herbals and folk records from the 1700s and 1800s listed it for chesty coughs and hoarseness. It was also taken as a gentle laxative and as a bitter for weak appetite.
Older European writers gave it for complaints of the liver and bile, and for what they called melancholy. Those ideas rest on a medical model no longer used.
The sweet root was a children's treat in parts of Norway and Sweden. It was also used in small amounts to flavour other medicines.
These records describe custom and belief. They were not written down as tests of whether it helped.
Who should avoid Common polypody?
- Do not use if you are pregnant or breastfeeding, as safety is unknown and the root can loosen the bowels.
- Never use it if you have a bowel blockage, severe belly pain of unknown cause, or you are vomiting.
- Do not use if you have inflammatory bowel disease (long-term gut inflammation, such as Crohn's disease or ulcerative colitis).
- Do not use if you take digoxin (a heart medicine) unless your doctor agrees.
- Do not use if you have hypokalaemia (low potassium) or take water pills or steroid tablets that lower potassium.
- Do not give it to children unless a doctor advises it.
- Avoid it if you have ever reacted to ferns with a rash, itching or wheeze.
- Never pick wild ferns yourself unless you can identify them with certainty; bracken is a look-alike and contains a cancer-causing compound.
- Do not use it as a daily laxative for weeks on end.
When should you see a doctor?
Stop and see a doctor if you get diarrhoea that lasts more than two days, or cramping that does not settle.
See a doctor if a cough lasts more than three weeks, or if you cough up blood, lose weight or get short of breath.
See a doctor if constipation lasts more than a week, or you notice blood in your stool.
Get emergency help for swelling of the lips, face or throat, trouble breathing, or fainting.
Is Common polypody legal where you live?
In the UK and EU it is sold as a herbal tea or food supplement. It holds no licence as a medicine, and no registered traditional herbal medicine claim.
In the United States it is sold as a dietary supplement, which means it is not reviewed for effect before sale.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
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