Yellow-flowered perennial used medicinally for centuries; flowers around the summer solstice. Considered invasive in Australia and parts of North America.
Hardiness ratings
| System | Rating | Temperature range | How to read it |
|---|---|---|---|
| USDA hardiness zone | Zone 3–9 | −40 °C to −1.1 °C | Plant tolerates down to this zone |
| RHS hardiness rating | H7 | down to −20 °C | Plant needs at least this level of cold tolerance |
| Canadian plant hardiness zone | Zone 3–9 | −34 °C and warmer | Plant tolerates down to this zone |
| Australian (ANBG) zone | Zone 1–5 | −15 °C to 10 °C | Plant tolerates down to this zone |
Growing notes
- Declared a noxious weed in several Australian states — check local rules before planting
- Always consult a qualified medical or herbal practitioner before medicinal use.
Pet caution: St John's wort is listed as potentially harmful to cats and/or dogs. Keep pets from grazing on it, and contact a vet if you suspect your animal has eaten some.
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Related plants
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