The medicinal power of common oak fern

Common oak fern is a species of fern that occurs naturally in much of the Northern Hemisphere. In North America you will find it in Canada and the eastern US. In Europe it grows extensively in Scandinavia, France, Germany, the Netherlands and Belgium. It likes to grow on rocks and cliffs and in forests where a rocky surface predominates. It does not grow higher than 30 centimeters. The root of the oak fern is edible. It has traditionally been a medicinal plant and is still used today in phytotherapy, especially for reduced liver and bile function, constipation and jaundice. NB! This article is written from the personal view of the author and may contain information that is not scientifically substantiated and/or in line with the general view.


  • Traditional use
  • Naming
  • Active substances
  • The laxative effect of oak fern
  • Oak fern for respiratory diseases
  • Dose and safety
  • Visit a doctor or herbal therapist

Traditional use

The root of oak fern is eaten. It has a bittersweet taste. Sometimes it is used as a flavoring agent for nougat. The oak fern root contains the saponin osladine, which is 500 times sweeter than sugar. Osladine was discovered in 1971. The carrot also contains the sweet carbohydrates glucose, fructose and sucrose. Furthermore, in traditional folk medicine of Europe, oak fern root is seen as a laxative and vermifuge. You could expel the tapeworm with it and then immediately remove it from the body.


In Latin, oak fern is called Polypodium virginianum . Poly means ‘many’ and podium is the Greek word for ‘foot’. Virginianum means ‘From Virginia’. Virginia is the name of an American state where the plant occurs. In German the plant is called Gewöhnliche Tüpfelfarn. In English it is called common polypody. A synonym in Latin is Polypodium vulgare. In Dutch we call the plant not only oak fern, but also angel sweet. That refers to the sweet taste of the carrot. By the way, the plant is sometimes also called Engelsüß in German.

Active substances

The root of oak fern is mainly used for phytotherapeutic purposes. The magazine can be used, but that doesn’t happen often. The carrot contains saponins such as polypadosaponin and osladine. It also contains the carbohydrates sucrose, fructose and glucose, essential oil, catechol tannin, mucilage, starch, fatty oil, phloroglucine derivatives, glycyrrhizin, the bitter substance samambaine and the resin that has antihelminthic or vermifuge properties.

The laxative effect of oak fern

Oak fern root has a mild laxative effect. This is mainly because the bitter substances in the root provide a bile-boosting effect. Because the bile works better, the liver receives more juices to digest the food. Digestion is more efficient and therefore faster and more effective. A liver that no longer works properly generally causes constipation. Due to this medicinal effect, oak fern is prescribed in phytotherapy for:

  • Hepatic insufficiency or weak liver function,
  • Constipation,
  • Icterus or jaundice.

Oak fern for respiratory diseases

Oak fern has an expectorant effect. It promotes coughing up and loosening of mucus. The mucilages contained in this plant are mainly responsible for this. That is why it is used for all kinds of respiratory diseases such as chronic bronchitis and chronic cough.

Dose and safety

Oak fern on the rocks / Source: David Eickhoff from Pearl City, Hawaii, USA, Wikimedia Commons (CC BY-2.0)

There are a number of ways to use this medicinal plant.

  • Mother tincture: 25 drops three times a day.
  • Carrot powder: 2 to 4 grams daily, 1 gram with each meal.
  • 10 grams of a decoct (10%) three times a day.
  • 1 gram of liquid extract three times a day.

No side effects are known at these therapeutic doses. Dried carrot is more active than fresh carrot.

Visit a doctor or herbal therapist

Much of the information about the medicinal plant mentioned in this article comes from the book Groot Handboek Medicinal Plants by Geert Verhelst. That is a handbook in phytotherapy. However, it is not suitable for self-healing. Anyone who suffers from something should consult a doctor or herbal therapist for a good diagnosis and choice of the best remedies, tailored to your personal situation. The knowledge and science mentioned here is of a purely informative nature.