Is Fennel Poisonous?

Hesta the Junkie with a craving for juicy young fennel shoots seen in her owners garden near Arundel.


Is Fennel poisonous to horses?


Letter: Please could you tell me if fennel is poisonous to horses? Our mini Shetland has lived in our garden for 6 years and we have not introduced any new plants or herbs.


Last Friday she rapidly went down hill from what we thought was a bout of colic, to the vet not thinking she would survive the night. At her worst she had mucus coming from her nose and mouth which smelt obnoxious, she couldn’t stand properly or focus as though she were drunk. Her temperature and heart rate was ok. She did survive the night and was not as unsteady on her feet. Her bloods showed a high white cell count. She was admitted to hospital for fluids. An endoscopy showed a small inflammation to her throat. She wanted to eat and drink, but couldn’t use her muzzle, as though it was anaesthetised. She could yawn and kept shaking her head. As the day progressed she gradually regained use of her muzzle. 3 days on, she is still quiet although is eating and drinking. The only thing we found in the garden were new shoots of fennel which appeared to have been grazed. The larger plants were untouched.


Please could you advise, if you have come across this before, and what the likelihood is of it being the fennel?


Thank you for your time, Denise




Re: Fennel (Foeniculum vulgare) and near cousin Aniseed (Pimpinella anisum), Star Anise (Illicuim verum). To answer your question, Fennel in small quantities is not poisonous to horses. However, a mini Shetland feasting on Fennel shoots ingesting several times the safe dose is a different story. Fennel contains a volatile oil, the principal constituents being Anethol about 50% to 60%, this has expectorant properties and in excess could cause the excessive mucous you describe. Anethol is also in large amounts sedative and hallucinogenic, which accounts for the staggering and drunkenness.


Anethol is present in the essential oil of Anise as a principal constituent approximately 90%. Essential oil of Anise is found both in Aniseed (Pimpinella anisum) and Star Anise (Illicuim verum). This same volatile oil when mixed with spirits of wine forms the liqueur Anisette.


Yes, Fennel in excessive quantities could bring on the symptoms you describe. The practical solution would be to move the fennel away from the fennel addict who probably loves the liquorice taste.

Leave a Comment

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

Scroll to Top