Definition of St. John's wort in US English:

St. John's wort

(also St. Johns wort)


  • A herbaceous plant or shrub with distinctive yellow five-petaled flowers and paired oval leaves, used in medicinal preparations to treat various disorders, including depression.

    Genus Hypericum, family Guttiferae: many species, in particular H. perforatum

    • ‘Psychiatrist Dr David Wheatley has published two independent clinical trials which shows that 60% of patients with mild to moderate depression respond to St John's wort.’
    • ‘Products such as St John's wort may act as a mild monoamine oxidase inhibitor or as a serotonin reuptake inhibitor.’
    • ‘Taken internally, St John's wort is used for mild to moderate depressive moods, anxiety, and nervous unrest.’
    • ‘Marie-Ange began by lighting the candle, which was a hollow tube infused with honey and herbs including sage, St John's wort and camomile, which are believed to have medicinal and healing properties.’
    • ‘The widely used herbal remedy St John's wort appears to amplify the action of the popular blood-thinning drug clopidogrel, sold as Plavix, a small new clinical study finds.’


So named because some species come into flower near the feast day of St John the Baptist (24 June).