Polemonium caeruleum, known as Jacob's-ladder or Greek valerian, is a hardy perennial flowering plant. The plant produces cup-shaped, blue or white flowers. It is native to temperate regions of Europe. It is the type species of the phlox family, Polemoniaceae.

Polemonium caeruleum (Jacob's Ladder) is an erect perennial prized for its loose sprays of cup-shaped, deep blue flowers, 1 in. across (2.5 cm), adorned with prominent yellow stamens in mid to late spring. Borne atop stiff leafy stems, they rise well above the foliage mound of finely divided, fern-like, bright green leaves.

Polemonium caeruleum, commonly known as Jacob’s ladder or Greek valerian, is a species of flowering plant in the Polemoniaceae family. This lovely plant is native to the temperate regions of Europe and Asia. It grows most often in rocky areas, woodlands, damp grasslands, and meadows. Jacob’s ladder is more than meets the eye.