- Klamathweed, St. John's wort, Goatweed, Tipton weed
- A densely branched, erect herbaceous perennial, 1-2 feet tall.
- oblong or linear
- black or translucent dots
- two edged (two raised lines that make the stem look pressed flat)
- Golden yellow five-petaled flowers with transparent or black dots on petals and numerous prominent stamens. Flowers grow in terminal cymes.
- capsule reddish-brown, 3-chambered, ovate, sticky, 5-10 mm long, styles persist
- seed shiny, black to brown, cylindrical, densely pitted, coated with gelatinous material
- roadsides, disturbed areas
- seeds dispersed by water and by sticking to farm machinery, shoes and animals
- pieces of broken rhizomes can develop into new plants
Key ID Features:
- golden yellow 5 petaled flowers
- numerous stamens
- translucent or black dots on leaves and petals
- Dwarf St. Johnswort (Hypericum mutilum) may resemble common St. Johnswort. It is a rare or uncommon erect plant less than 0.6 m tall. It has flower petals about 2 mm long, petals that are equal to or slightly shorter than the sepals, and 1-chambered capsules.
- Under ideal conditions St. Johnswort can be aggressively competitive and spread rapidly by seed and rhizomes. After disturbances such as logging or fire outbreaks of the plant can sometimes occur.
- On Nantucket, this species tends to exist in small, dense stands.
Growth Form: Herb
Origin: Europe, Asia
Level of Invasiveness for Nantucket: Do not list at this time
Level of Invasiveness for Massachusetts: Not evaluated
Massachusetts Cultivation Restrictions: no