Great St. John's-wort

Native range — southern Siberia, the Russian Far East, northeastern and central China, Japan, and eastern North America.

A perennial with an erect four-angled stem up to 120 cm tall, sometimes slightly branched in the upper part. Leaves opposite, oblong-ovate, stem-clasping, acute, 6—10 cm long, glaucous beneath, entire, with numerous translucent glands. Flowers regular, with a double perianth, five-parted, as in all other species of this genus. Flowers very large, up to 4.5—8 cm in diameter, solitary or in groups of 3—5 at the ends of branches.

Calyx deeply five-parted, 2—3 times shorter than the corolla; sepals ovate, obtuse, about 1.5 cm long, less often elongated — up to 4 cm. Corolla composed of five yellow petals. Stamens numerous, grouped into 5 bundles. Ovary superior, five-celled, brown, 5—7 mm long. Five styles united at the base. Fruit a capsule, oblong-ovoid, up to 2 cm long, brown. Seeds oblong, 1.5 mm long, brown, with a membranous wing. Flowers in July—August. Fruits ripen in September.