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Hypericum perforatum
Also called Perforate St John's-wort, St John's wort, Common St. John's Wort, St. John's Wort, Klamath Weed, Perforate St. John's Wort, Goatweed
St. John's wort is a hardy, weedy perennial herb with yellow flowers and woody roots that spreads readily by seed and rhizomes. It thrives in sunny, open, well-drained sites and is often treated as a wild or invasive weed.
Hypericum perforatum, commonly known as St. John's wort (sometimes perforate St. John's wort or common St. John's wort), is a flowering plant in the family Hypericaceae. It is a hairless, perennial herb with woody roots, yellow flowers marked by black glands, and leaves that appear perforated due to translucent glands, producing thousands of seeds per plant.
H. perforatum is the type species of its genus, known for its historical use in folklore and traditional medicine. Probably a hybrid between the closely related H. attenuatum and H. maculatum (imperforate St. John's wort) that originated in Siberia, the species has spread worldwide. It can further hybridize with related species due to its allopolyploid nature.
Use of H. perforatum may produce adverse effects when combined with other antidepressants through an increase in brain serotonin levels called serotonin syndrome, which may be life-threatening and is associated with rapid heart rate, acute hypertension, mydriasis, and fever. Photosensitivity and acute neuropathy upon sun exposure, and reduced response to chemotherapy are other possible effects.
Common side effects of St John's wort products are headache, nausea, fatigue, dry mouth, sleepiness, and gastrointestinal upset. It should not be consumed during pregnancy and breastfeeding.
Text excerpted from the Wikipedia article Hypericum perforatum by its contributors, under CC BY-SA 4.0; the excerpts and the care summary drawn from them are shared under the same licence.
The care summary was written by AI (Claude, Anthropic) from the sources on this page, with general growing knowledge where they are silent. Check before relying on it.
Life form, climate and native range: World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 3.0), reformatted; see Plants of the World Online.
Pet safety from the ASPCA toxic and non-toxic plant lists.
