Klamathweed
Hypericum perforatum
Last reviewed: June 2026
Klamathweed is toxic to dogs and cats.
Listed as toxic by the ASPCA Animal Poison Control Center (last reviewed 2026-05-21). If your pet has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435and your veterinarian's emergency line.
Pollinator Patch flags toxic plants so you can choose a pet-safe native alternative for your yard.
Light
part shade
Water
low
Size
12"–24" H × 12"–18" W
Bloom
Jun, Jul, Aug, Sep
Native to
MA
Pollinators
bees, beetles
Browse plants for this ecoregion
St. John's wort is a low-growing perennial herb with bright yellow flowers that bloom from summer into early fall. This compact plant forms neat clumps and tolerates partial shade and dry conditions well. The flowers are attractive but the plant can spread aggressively in some conditions.
In an HOA neighborhood
Klamathweed takes more care to keep looking intentional in a front yard. Maintenance level: moderate. Consider it for backyard or mid-zone beds rather than the street edge.
Works well in: backyard only.
- Non-native invasive species
- Can spread aggressively
- May be considered a weed by neighbors
Wildlife value
The bright yellow flowers attract bees and beetles during the long summer blooming period. However, this non-native plant provides limited overall wildlife value compared to native alternatives.
Native range data from the USDA PLANTS Database and regional native plant society lists. Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.
Pollinator Patch flags toxic plants like Klamathweed and shows pet-safe natives for your ecoregion instead.