Limited distribution in Utah. High priority to eradicate all known populations and prevent new ones.
Quick Facts
Report your sighting through EDDMapS to help us track and respond to new infestations.
Report on EDDMapSCommon St. Johnswort
Hypericum perforatum
Overview
Common St. Johnswort is a perennial herb from Europe that invades rangelands, roadsides, and disturbed areas. It contains hypericin, a photosensitizing compound that causes severe skin reactions and blindness in livestock, particularly in light-colored animals.
How to Identify
Perennial 1-3 feet tall. Bright yellow 5-petaled flowers with black dots along the margins. Leaves are oval with translucent dots visible when held up to light. Spreads by both seeds and rhizomes.
Control Methods
Biological control using the Chrysolina beetle is very effective and widely used. Herbicide treatment for new infestations. Competitive seeding with desirable species.
Herbicide Recommendations
Picloram, clopyralid, or 2,4-D. Biological control (Chrysolina beetles) is preferred for established infestations.
⚠️ Always read and follow pesticide label directions. Contact your county weed superintendent for site-specific recommendations. Permits may be required near water.
Need help managing this weed?
Skyline CWMA can connect you with technical assistance, cost-share programs, and licensed contractors for treatment on your property.
