How to grow Polemonium (Jacob’s ladder)

Polemonium caeruleum is a hardy, early summer flowering perennial that does well in partial shade. It’s known as Jacob’s ladder because of its ferny foliage on alternate sides of its stem, resembling a ladder. The name also refers to the bible story where Jacob dreams of a ladder ascending to heaven.

The upright stems produce clusters of bell-shaped lavender or white flowers in June. Cultivars include the white flowered variety ‘White Pearl’ or the lavender flowered ‘Brise d’Anjou’, which is grown for its striking bright green, variegated foliage. It’s a prolific self seeder, which is a bonus if you want extra flowers for free. To restrict its spread, deadhead the plants before they release their seed or collect the seed to sow yourself.

Jacob’s ladder is the perfect cottage garden plant, happy in partial or dappled shade, beneath deciduous trees, in a wildlife or woodland garden or in flower borders that don’t receive too much direct sun. It also grows well in grassy areas.

How to grow polemonium

Jacob’s ladder (polemonium) is a low-maintenance plant that does best in a partially shady spot. It has bell-shaped flowers on tall stems in late spring to early summer and could be planted beneath trees or in a border. It’s deciduous and will die down in the autumn.

Where to grow polemonium

Choose a partially shaded spot for this plant as it will struggle in soil that dries out too often. Ideally, it needs moist, well-drained soil. It will do well in a border or growing in grass.

How to plant polemonium

Plant Jacob’s ladder in early spring or autumn while the soil is warm and moist, to give it the best chance to establish and put down roots before the summer. Water well before planting and plant it at the same depth as it was in its pot. Firm in and water regularly after planting.

How to care for polemonium

Jacob’s ladder is a low-maintenance plant and doesn’t need much care. Keep it well watered until established. Deadhead regularly to encourage more flowers and cut out any dead stems. Once it’s finished flowering, cut back the plant to encourage another flush of flowers. Polemonium doesn’t need pruning. Cut down the plant in the autumn to ground level. Mulch around plants in the border in autumn or spring to keep moisture in the soil.

How to propagate polemonium

Jacob’s ladder self-seeds freely around the garden, but to control where new plants appear, collect the seeds and raise young plants yourself. Wait until the faded flowers have turned into dry, brown pods. Collect these and store the seeds in a paper bag. You can sow in autumn and overwinter the small plants undercover or save the seed and sow in the spring, but bear in mind that those plants won’t flower that year. Alternatively you can buy seed, sow in autumn or under cover in early spring for flowers in the same year.

Divide plants in spring to make more plants. Dig up the plant in early spring. Separate the root ball into sections, pulling the clumps apart with your hands. If it’s a big clump, use a spade to split it in half or into smaller sections. Replant each section, firming them in well.

Pests and diseases

Polemonium isn’t attacked by any particular pests but a white powdery substance on the leaves could be powdery mildew. Cut out and destroy any affected foliage and in autumn. To prevent it from reoccuring, avoid the leaves when watering and don’t plant susceptible plants too close together to increase air circulation.