A close look at the foliage of Jacob's ladder (Polemonium caeruleum) explains its common name. Evenly divided leaves run up the stem like rungs on a ladder. In early summer, airy clusters of blue flowers appear above the arching, fernlike foliage.
Large plantings of this North American native, set in an expansive, woodland setting, will provide a sea of blue when in bloom. While you can also grow Jacob's ladder in sun, it's a frequent companion for perennials that like dappled shade, such as Siberian bugloss (Brunnera macrophylla), Virginia bluebells (Mertensia virginica), and spotted dead nettle (Lamium maculatum).
Common name: Jacob's ladder, Greek valarian
Botanical name: Polemonium caeruleum
Plant type: Perennial
Height: 12 to 36 inches
Zones: 4 to 9
- Sun: Sun or dappled shade
- Soil: Average, well-drained soil
- Moisture: Evenly moist
- Mulch: Add 2 inches of organic mulch to keep soil cool and moist.
- Fertilizer: Use one application of balanced fertilizer in the spring, if needed.
- Pruning: Cut spent flower heads in summer.
- ‘Brise d'Anjou' (pictured above) has arching sprays of variegated foliage and a light showing of blue flowers in the spring. It grows in part to full shade (full shade in southern regions) and does best with some winter mulch, applied after the ground freezes. It grows 18 to 24 inches tall. Zones 4 to 8.
- P. caeruleum var. album has white flowers, green foliage, and grows 12 to 36 inches tall. Zones 4 to 9.
- In southern regions, Jacob's ladder does best in part shade. In northern regions, it does fine in sun.
- In sunnier garden locations, combine Jacob's ladder with cushion spurge (Euphorbia polychroma), small shrub roses, or columbine (Aquilegia spp.).
Pests and diseases
- Powdery mildew may occur on the foliage. Provide good air circulation to discourage fungal diseases.
- Divide plants in late summer.
- Take cuttings in late summer.
All in the family
- Leafy polemonium (Polemonium foliosissimum) is a larger version of Jacob's ladder. It grows 32 inches tall with bell-shaped blue, ivory, or white flowers in early summer. Zones 4 to 8.
- P. reptans is a shorter Jacob's ladder. ‘Blue Pearl' has fragrant blue flowers. Place it where it will get late-day shade. Grows 12 inches tall. Zones 3 to 8.
Text by Mary Pestel, photo courtesy of Blooms of Bressingham