Polemonium caeruleum, known as Jacob's-ladder[2] or Greek valerian, is a hardy perennial flowering plant.

The plant produces cup-shaped, blue or white flowers.

[3] The plant normally prefers soil that is rich in moisture and lime with partial shade.

Leaf spot and powdery mildew can be problems, particularly in humid climates.

[3] Polemonium caeruleum was voted the county flower of Derbyshire in 2002 following a poll by the wild plant conservation charity Plantlife.