Klamathweed
Hypericum perforatum
Last reviewed: August 2026
Klamathweed is toxic to dogs and cats.
Listed as toxic by the ASPCA Animal Poison Control Center (opens in new tab) (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
Pollinators
bees, beetles
Native alternatives to Klamathweed
Klamathweed is not native to the United States. These natives fill a similar role in a planting, matched on bloom season, bloom color and mature size.
Before you buy
Your city may pay you to plant this
Cities and water utilities offer rebates for replacing lawn with native and water-wise plants. We track 452 programs across 44 states, each with a link to the provider and the date we last checked it.
Find rebates in your areaSt. 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.
Common questions
- How much sun does Klamathweed need?
- Klamathweed grows best in part shade conditions.
- When does Klamathweed bloom?
- Klamathweed blooms in June, July, August, and September.
- Is Klamathweed toxic to dogs?
- Yes. Klamathweed is listed as toxic to dogs by the ASPCA Animal Poison Control Center (aspca.org). If your pet has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435.
- Is Klamathweed toxic to cats?
- Yes. Klamathweed is listed as toxic to cats by the ASPCA Animal Poison Control Center (aspca.org). If your cat has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435.
- What pollinators does Klamathweed attract?
- Klamathweed draws bees and beetles.
- Is Klamathweed HOA-friendly?
- Klamathweed takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.
Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.
If something looks wrong
Common plant problems, and what to check first
These come up on almost any plant. Each guide lists the likely causes in the order they are worth ruling out, with one thing to check before you act on any of them, and links to the source it came from.
- It is dying right after planting
- Leaves turning yellow
- Wilting even though I watered it
- Brown crispy leaf tips
- Bugs on the plant
Pollinator Patch flags toxic plants like Klamathweed and shows pet-safe natives for your ecoregion instead.
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