Saint John'swort

Hypericum perforatum

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Also called Klamath weed. Height to 5 ft., usually closer to 2 ft. Five-petaled yellow flowers with black dots; flowers June to August. Leaves are oblong and have translucent dots.


Occurs in fields, forest edges, and pastures; sunny areas that are well-drained, prefers sandy soils.

Location in Nebraska

Fairly widespread throughout Nebraska.

Pathway of Introduction and Spread

Originally from Europe for landscape use, but has escaped into natural areas. Used as a remedy for depression. Seeds spread by animals, wind, and water; colonizes by rhizomes and stolons.


A single plant can produce 15,000-30,000 seeds; Forms dense colonies and can be toxic to livestock. Competes with native vegetation.

Photo Credits: 

“Weeds of the Great Plains” – Nebraska Department of Agriculture