They are perennial herbaceous plants with blue or sometimes white flowers that open from pink-tinged buds.

Mertensia is native to most of North America and to a large part of Asia from western China to northeastern Russia.

Section Mertensia consists of all of the North American species plus M. rivularis, a denizen of the Russian half of the Beringian floristic region.

[11] Albrecht Wilhelm Roth, in 1797, separated what are now M. virginica, M. maritima, and M. sibirica from Pulmonaria to form the genus Mertensia,[6] based on their smaller and differently structured calyx, their different anther position, and the presence of nectar glands on the inner surface of the corolla.

[20] The section Stenhammaria was named for the Swedish naturalist and clergyman Christian Stenhammar, who is best known for his work in lichenology.

After Gray completed his monograph of Mertensia, many species were discovered by botanical expeditions in the western United States.

[21] This reclassification has been confirmed by molecular phylogenies which place Pseudomertensia closer to Myosotis than any of the genera that have been sampled so far.

More recently, molecular phylogenetics has greatly clarified the ancestral and derived character states in Mertensia.

Ancestral states in Mertensia include short plant height (< 40 cm), long stamens (> 1.5 mm), filaments inserted higher in the corolla, calyces divided at least 2⁄3 of the way to the base, and acute to acuminate calyx lobe apices.

Their derived alternatives are greater plant height (> 40 cm), short stamens (< 1.5 mm), filaments attached lower in the corolla, and calyces divided less than halfway to the base, and obtuse calyx lobe apices.

A molecular clock analysis has estimated that Mertensia diverged from Asperugo in the late Oligocene or early Miocene.

[1] Mertensia originated in Asia and dispersed over the Beringian land bridge to North America.

Most of the groups that originated in Asia are more diverse there,[23][24] but Mertensia is a conspicuous exception in having most of its species in North America.