Hypericum majus, the greater Canadian St. John's wort, is a perennial herb native to North America.

H. majus differs from its relative in its annual habit, thinner leaves, smaller flowers, and doubly branching inflorescence.

The two species became sympatric when north-eastern North America became glaciated and the two now hybridize, most notably in Wisconsin.

Hybrids of the two species are shorter than H. majus and have leaves of intermediate length, width, and vein number.

The hybrid of latter can be distinguished by its intermediate seed capsule shape, similar to H. × dissimulatum though with more broad leaves.

[4] Hypericum majus is a perennial bearing short leafy shoots with solitary or tufted stems.

The roots are fibrous and lack rhizomes or runners but can grow short offshoots in autumn.

The twelve to twenty-one stamens are obscurely five-fascicled, the longest measuring 2.5–3.5 mm (0.098–0.138 in).

[8] Hypericum majus grows in wet or dry open soil in bogs, marshes, ditches, meadows, woodlands, and other damp habitats.