This shrub is native to the Great Lakes region and grows to a size of about 1 to 4 feet tall. In July and August, the plant blooms with yellow flowers that complement its blue-green leaves. Found naturally growing along lakes, rivers, and cliffs, Kalm’s St. John’s Wort is the most cold-hardy species within the Hypericum genius, and it is especially well-adapted to growing in moist, alkaline soils.
Though it prefers wet to moist conditions, it can also temporarily tolerate shallow water, making it suited to the changing water conditions of a Michigan rain garden. Various bees pollinate the plant as they collect nectar from the flowers. Its shallow, spreading root system can help filter stormwater runoff as it drains through the soil.
(Click on images for a larger view.)