The medicinal power of water beetle herb

Water beetle grows in moist soil, swamps or in water. Water beetle is an annual plant that can grow to a height of one and a half meters. It originally grows in Europe and Asia up to Siberia. It has white flowers and is very similar in appearance to fennel; hence it is called water fennel. The water fennel has lacecap flowers, just like regular fennel. Unlike some closely related species, the plant cannot be eaten. It is even a poisonous plant. The fruit of this plant is used medicinally in phytotherapy, albeit in very small quantities; 100 to 200mg each time. This plant is also used in homeopathy. 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.

Botanical drawing of water beetle / Source: K√∂hler’s Medizinal Pflanzen, Wikimedia Commons (Public domain)


  • The poisonous water beetle herb
  • Water beetle herb in traditional medicine
  • Naming
  • Active substances
  • Medicinal effects of water beetle herb
  • Dose and safety

The poisonous water beetle herb

It is a poisonous plant for horses, but cows can tolerate the leaf well. However, if they eat the root, a cow can die. There have been many cases of poisoning among humans and animals from water beetle weed, or its drier brother, beetle weed. As is often the case, a poisonous plant is a medicinal plant as long as you take minute doses of the plant. Water beetle herb has traditionally been a medicinal plant for coughs and flatulence and it is used to increase urine production.

Water beetle herb in traditional medicine

The fruit or seed of water beetle is diaphoretic, a diuretic, has an expectorant effect and is a tonic for the lungs. It is used in the treatment of chronic conditions such as dyspepsia, intermittent fever and persistent ulcers. This plant should be used with caution and should only be taken under the guidance of an experienced physician. If too much is taken it can cause dizziness and poisoning.


In Latin, water beetle is called Oenanthe aquatica . In Dutch, water fennel is an alternative name. The leaves of the plant look a bit like those of a fennel plant. A Latin synonym of this plant is Oenanthe phellandrium . There is also a plant called beetle herb. This has almost the same medicinal properties as water beetle herb. The Latin name of beetle herb is Oenanthe fistulosa . It is closely related to water beetle; the Latin similarity in name also indicates this. Alternative Dutch names for beetle herb are Grape flower, Pipe herb and Fragrant water rushes. In German, water fennel is called Wasserfenchel; that’s the main name. In English this plant is called fine-leaved water-dropwort, but it is also called water fennel. In Old Dutch the plant was called common waterchervil. It was given this name because its growth habit is somewhat similar to that of chervil.

Oenanthe aquatica, water fennel or water beetle / Source: Christian Fischer, Wikimedia Commons (CC BY-SA-3.0)

The medicinal properties of water beetle herb are similar to those of fennel. Water beetle herb is less strong.

Active substances

The fruit of water beetle herb is used for phytotherapeutic purposes. It contains the following important active ingredients: essential oil including betafellandrene, pinene and sabinene.

Medicinal effects of water beetle herb

  • Water fennel or water beetle is a weak carminative. It can therefore be used for flatulence and meteorism or abdominal distension.
  • Water beetle herb is a mild expectorant and antitussive. It can be used for cough and bronchitis.
  • Water beetle herb is diuretic and diaphoretic. This makes it an herb that can purify the blood.

In homeopathy, water fennel is a plant that is used for respiratory diseases, digestive disorders, gastritis and as an adjuvant for tuberculosis.

Dose and safety

There are three ways to use this medicinal plant.

  • 40 drops of mother tincture three times a day.
  • A cup of tea made from 0.5 to 2 grams of seeds several times a day.
  • 100 to 200 mg of fruit powder per day, gradually increasing to 1 to 6 grams per day.

Anyone who uses the above therapeutic doses should not expect side effects. If you take too much water fennel, you run the risk of becoming dizzy and having an anxiety attack.