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St. John's Wort
Hypericum perforatum
セイヨウオトギリ
A perennial in the Hypericaceae/Clusiaceae family, native to Europe and naturalized worldwide, including Japan. In summer, many bright yellow 5-petaled flowers open; held to the light, the leaves show translucent oil glands. Known as 'St. John's Wort' in Western herbalism for treating mild to moderate depression, with hypericin and hyperforin as active ingredients. Notable for many drug interactions — especially with oral contraceptives and anticoagulants.
Identification Points
- ✓Many bright yellow 5-petaled flowers
- ✓Translucent oil-gland dots on leaves
- ✓Reddish-brown erect stems, 30–60 cm tall
Habitat
Grasslands, roadsides (naturalized)
Season
June to August (flowers)
Morphological TraitsAI-estimated, needs verification
Leaf arrangement
Opposite
Leaf type
Simple
Leaf shape
Ovate
Growth form
Herb
Petal count
5 petals
Flower color
Yellow
Flowering season
Summer
Habitat
Grassland
Phylogenetic Positionオトギリソウ科 →
Phylogenetic Position
Angiosperms > Eudicots > Core eudicots > Malpighiales > Clusiaceae
Divergence Era
Late Cretaceous to Paleogene (about 80–70 million years ago)
Sources & References
AI-generated, needs verification