Polemonium caeruleum aka Jacob's Ladder

Polemonium caeruleum, or Jacob's ladder, belongs to the Polemoniaceae family. This leafy perennial forms clumps and loses its leaves each year. RHS places its native range in temperate Eurasia, including Britain and Ireland. PFAF also lists it across northern parts of North America. It grows beside streams and along woodland and swamp edges. Some wild sites lie on grassy slopes in limestone hills.

Garden plants reach about 1.6–3.3 feet [0.5–1 metre] tall. Chicago Botanic Garden gives a shorter height of 2 feet [0.6 metre]. Clumps spread about 0.3–1.6 feet [0.1–0.5 metre] wide. The mid-green leaves are pinnate, with leaflets set like ladder rungs. Chicago records 19–27 leaflets on each leaf. The plant has little hair, except near its flowers. RHS describes stiff flower stems, while Chicago notes looser stems below them. Plants take two to five years to reach full size.

Blue flowers rise above the leaves in loose groups. Each flower spans about an inch [0.025 metre], with clear yellow stamens. Chicago describes the blooms as drooping and bell-shaped. Its records place flowering from March through June. RHS gives early summer as the main flower season. The blooms draw butterflies, and deer tend to leave plants alone. Plants can scatter seed freely around the garden. Their leaves and flowers suit border fronts and woodland gardens. They also fit rock gardens, cottage gardens, and natural-style beds.

Grow this plant in fertile soil that stays moist but drains well. It accepts clay, loam, or sand across acid to alkaline soils. RHS allows full sun or part shade. Chicago also lists full shade as a suitable exposure. Too much sun can scorch the leaves. Dry soil can turn the leaflet tips brown. Moderate watering helps meet its need for moisture. RHS rates it H7, while Chicago lists USDA zones 2–7. Sow seed in a cold frame during spring or autumn. Divide clumps in spring, and cut old leaves down after the season.

Pests and diseases rarely cause serious trouble, but slugs need watching. Leaf spot and powdery mildew can occur in humid weather. The leaves may look worn as summer goes on. PFAF lists no known food uses or hazards. That record does not establish safety for people or pets. It reports past use for headaches, fever, and epilepsy. These are historical uses, not proof that treatment works.