St Johns-wort (Hypericum perforatum)
2B, widespread in Montana
Quick ID
- Tiny, transparent glands resembling perforations on the leaves
- Bright yellow flowers with five petals and several stamens
- Glands resembling black dots line the petals
- Opposite leaves
- Woody at the base and rust colored (most visible in autumn)
St Johns-wort
Video Information
Weed Images
Weed Specifications
| Type | Information |
|---|---|
| Toxicity | Toxicity may result in photosensitivity. Light-haired cattle, horses, and sheep are most susceptible. |
| Best Management Practices | Mechanical, chemical, and biological control. |
| Habitat | Grows in well drained, gravelly or sandy soils; favors sunny exposures; favors lower elevations. |
| Root | Taproot may grow as deep as four to five feet. Lateral roots grow two to three inches beneath the soil surface. |
| Leaves | Leaves are opposite, sessile, elliptic or oblong, and tend to be less than one inch in length. |
| Lifespan | Perennial |
| Similar Looking Plants | Western St. Johnswort, Tinker's penny, Canadian St. Johnswort. |
| Important Information | Not a highly competitive plant so will persist in disturbed areas which lack other plant species. |
