Tall bluebells is an herb in the borage family (Boraginaceae) with drooping blue bell-flowers and large ovate leaves. Tall bluebells is a common species across the park, found in floodplains, meadows and open forest in the boreal zone extending into subalpine meadows and shrublands and occasionally in tundra. Mertensia paniculata grows 20-60 cm tall from a short caudex or rhizome. The stem has many leaves, and plant usually has a few are basal leaves (sometimes the only structure to emerge in a given year is a cluster of basal leaves). Leaves are long ovate with acute tips, up to 15 cm long, deeply impressed with a branching network of veins. The leaves have stiff white hairs. The lower leaves have long petioles; the upper leaves are short-petioled or sessile. At the top of the stem, plants produce open panicles of flowers (the source of the scientific name 'paniculata')—a loosely branched inflorescence, with each branch bearing a row of flowers. The heads are nodding, with a short calyx and a much longer, narrow bell for the petals (10-20 mm long). Both the flower stems and sepals are covered in white hairs. The tube is constricted at the base, broadening, and with five short lobes at the tip. In bud, the petals are pink, becoming blue. Fruits are four nutlets per flower, all attached at the center, each with a single seed. No other plant in Denali has similar panicles of drooping blue bell flowers.

Tall bluebells is relatively early flowering. The flowers in a panicle mature sequentially. The young flowers produce pollen, older flowers produce nectar. Bees often rob flowers of their nectar by chewing through the side of the corolla (Morris 1996). However nectar robbery does not appear to reduce fertility of flowers—bees will gather pollen from younger flowers of the same inflorescence. hypothesizes that the benefit of older flowers attracting pollinators outweighs the cost of producing nectar.

Mertensia paniculata is monoecious with bisexual flowers. Flowers are nectar-producing and bee-pollinated (Reeves 2006). Plants can also regenerate from rhizomes, but do not spread clonally (Hicks and Turkington 2000). Flowers separated from pollinators produced far fewer seeds (Morris 1996). Fruits are nutlets, dispersed by gravity and water.

This species prefers neutral soils, not growing in acid bogs or heaths.

Wide-ranging; usually occurs in moist to dry sites.