Jacob's ladder

Jacob's ladder: how do you recognise it?

Habit

Clump 45–60 cm tall and about 40 cm wide, with upright flower stems above a rosette of leaves.

Leaves

Pinnate, with about twenty narrow, pointed leaflets in two rows, like the rungs of a ladder; fresh green.

Flower

Cup-shaped, about 2 cm across, in loose clusters at the stem tips, with striking orange-yellow stamens.

Colour

Sky blue to lavender blue; also in white.

Fruit

Small capsules full of seed: it self-seeds readily.

Flowering: May–July · Sowing: March–May · Plants: March–May and September–October · Pruning: March and July

Why grow it?

• Bright blue flowers from May to July, a rare colour in the border.
• The pinnate foliage is decorative from spring to autumn.
• Bees and bumblebees love visiting the flowers.
• Easy and tough: it grows in sun or partial shade and is extremely hardy.
• After cutting back it produces fresh leaves and sometimes a small second flush of flowers.

Jacob's ladder: where does it grow best?

• Sun to partial shade; in full sun only if the soil does not dry out.
• Loam or clay rich in humus, acid to chalky.
• Normal soil that stays moist but is not waterlogged.
• Plant 30–40 cm apart, about seven plants per m².

Light

Sun and partial shade

Soil type

Loam or clay

Acidity

Not fussy

Moisture

Normal

Size

0.6 m tall, 0.4 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Lady’s mantle: Lime-green flower heads that contrast nicely with the blue.
• Columbine: Flowers at the same time, in the same partial shade.
• Peony: Large pink flowers beside the delicate blue clusters.
• Cranesbill: A low, flowering base in the same soil.
• Masterwort: Pink or white flowers that take over in summer.

Jacob's ladder: when and how to plant it?

Plant in March–May and September–October.

1. Plant from March to May or in September–October, when the soil is not frozen or waterlogged.
2. Dig a hole twice as wide as the pot and mix in compost.
3. Set the plant at the same depth as it was in the pot, with the rosette at soil level.
4. Firm the soil and water in thoroughly straight away.
5. Mulch with compost or leaf mould to keep the soil cool and moist.

Care

Water

Water in dry spells, especially in sun: otherwise the leaf edges scorch.

Feeding

A layer of compost in spring is enough.

Cutting back

After flowering, cut back to the leaves at the base: this limits self-seeding and gives fresh foliage.

Support

Usually not needed. On rich soil or in a windy spot a few twigs help.

Rejuvenating

It is often short-lived. Divide older clumps every three years or keep a few seedlings.

Tip: After flowering, cut back to the leaves at the base: you limit self-seeding and get fresh new foliage for the rest of the summer.

Jacob's ladder: when to prune it?

Pruning months: March and July.

When: In July, after flowering, cut the flower stems back. In March, clear away the old leaves.

How:

• Cut the spent flower stems back to just above the leaves at the base.
• If you want seedlings, leave a few stems until the seed is ripe.
• In March, cut away the dead leaves before the new rosettes start to grow.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Indoors in March in a seed tray, or outdoors in April–May. Cover thinly and keep moist; they germinate within a few weeks. Plant out once they are sturdy enough. Variegated forms do not come true from seed.

Division

In March–April or September, lift a clump and split it into pieces with a few rosettes each. Replant straight away and water.

Jacob's ladder: how does it get through the winter?

Hardy to −35 °C.

• Extremely hardy, to about −35 °C: no protection is needed in Belgium.
• Most of the foliage dies back; new rosettes appear in early spring.
• In a pot: stand it in a sheltered spot and do not let the compost dry out or become waterlogged.

Diseases and pests

• Powdery mildew: White powder on the leaves in dry summers. Water and cut back after flowering.
• Slugs: They eat the young rosettes in spring. Pick them off in the evening.
• Scorched leaves: Brown edges in hot, dry sun. Water, mulch or move it to partial shade.
• Too many seedlings: Cut back after flowering or weed out the young seedlings in spring.

Through the year

• March: Cut away old leaves. Sow indoors. Plant.
• April: Sow outdoors. Plant or divide.
• May: Flowering begins. Sow outdoors.
• June: Full bloom. Water in dry spells.
• July: Cut back after flowering for fresh leaves.
• August: Water in dry spells.
• September: Plant or divide.
• October: Plant.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The name Jacob’s ladder refers to the ladder to heaven in Jacob’s dream in the Bible: the leaflets are lined up like rungs.
• In French it is called ‘valériane grecque’, although it is not a valerian: the plant used to be known as Valeriana graeca because its leaves resembled those of valerian.
• Jacob’s ladder gave its name to a whole plant family, the Polemoniaceae, which also includes phlox.