Flower:

Single flowers or open clusters of a few to several flowers at the tips of stems and branches, with a pair of leaf-like bracts at the base of a flower stalk. Flowers are yellow, less than ¼ inch across with 5 narrowly oval petals with blunt tips. 5 green sepals behind the flower are about as long as the petals, lance-oblong with blunt tips. The center has 3 styles, united at the base, standing erect with the 7 to 18 slender stamens aligned closely around it.

Leaves and stems:

Leaves are simple, opposite and stalkless to somewhat clasping, oblong, oval or elliptic, 3/8 to ¾ inch long, 1/3 to ½ as wide, toothless, hairless, tips and base rounded or tapering to a blunt tip, with 3 to 5 prominent veins from the base. Stems are hairless, freely branching in the upper plant, and multiple from slender underground rhizomes, forming open spreading colonies.

Fruit:

Fruit is an upright, oval to ellipsoid capsule 1/8 to 3/16 inch long, reddish to deep purple.

Notes:

Northern St. John's-wort is one of two small-flowered Hypericum spp. found in Minnesota, the other is Larger Canadian St. John's-wort (Hypericum majus), which has a greater range and is the more common within their shared range. While the individual flower can appear nearly identical, H. boreale sepals are generally more oblong and blunt tipped, its flower clusters are few flowered, more leafy and open, and its leaves are more broadly oval and rounded at the ends. H. majus sepals are more lance-like and taper to a sharp point, its flower clusters have no leafy bracts, are more densely flowered, and its leaves are more narrowly lance-shaped with pointed tips.