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Klamathweed

Hypericum perforatum

Last reviewed: October 2026

Klamathweed (Hypericum perforatum)
Photo: (c) Thomas Gyselinck, some rights reserved (CC BY), uploaded by Thomas Gyselinck

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) 426-4435 and 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.

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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.

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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.

See all plant problem guides

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