Jacob's ladder (Polemonium caeruleum), also commonly known as Greek valerian, is a woodland-type wildflower with attractive bell-shaped flowers in its signature deep blue color. Jacob's ladder grows best in shady, moist conditions and requires only dappled sunlight, well-drained, and neutral soil, and cool summer temperatures. Jacob's ladder earned its common name due to the rung-like arrangement of its pinnate, light green leaves. The species form and its various cultivars send up clusters of flowers atop long stems in mid to late spring.
Direct seed in early spring and it will grow tall and start blooming in mid-spring, sometimes continuing into summer so you can continuously enjoy these fragrant and wildlife-resistant plants.
|Common Name||Jacob's ladder, Greek valerian|
|Botanical Name||Polemonium caeruleum|
|Plant Type||Herbaceous, perennial|
|Mature Size||12-30 in. tall, 12-24 in. wide|
|Sun Exposure||Partial, shade|
|Soil pH||Acidic, neutral|
|Bloom Time||Spring, summer|
|Flower Color||Blue, purple, white, pink, yellow|
|Hardiness Zones||4 to 9 (USDA)|
|Native Areas||Northern Asia, Europe; has naturalized in Eastern North America|
Jacob's Ladder Care
Here are the main care requirements for growing Jacob's ladder.
- Grow in average, well-drained, and consistently moist soil.
- Plant in shady locations, even where few flowering plants will thrive.
- Feed in early spring and again when blooms have faded.
- Deadhead spent flowers in the spring to prompt a potential second bloom period.
Jacob's ladder plants prefer partial or dappled shade. Varieties with dark green leaves can handle more direct sun than the variegated varieties, so long as the soil is kept consistently moist.
Plant Jacob's ladder in loose, rich, well-draining soil that will remain moist but not wet. It is fussier about moisture than about soil pH but does best with a relatively neutral or slightly acidic soil pH.
Jacob's ladder plants that receive regular watering will bloom longer and remain attractive into summer. Water regularly to maintain medium moisture levels but avoid soggy conditions. During dry periods, you may need to water more frequently to keep the plants lush.
Temperature and Humidity
Greek valerian prefers a relatively cool summer climate, and it can succumb to high heat in warm southern gardens. Very humid conditions can bring on leaf spot fungal diseases or powdery mildew.
Give the plants a boost in early spring with a dose of balanced fertilizer as the new growth is emerging. Feed them again once the faded flowers have been cut back.
Types of Jacob's Ladder
Look for these kinds of Jacob's ladder for your garden:
- Polemonium caeruleum 'Album': This variety has white flowers.
- P. caeruleum 'Bambino Blue': Beautiful light blue flowers adorn this variety.
- P. caeruleum 'Snow and Sapphires': With variegated leaves and blue flowers, it is somewhat hardier than the plant's similar cultivar 'Brise d'Anjou'.
- P. reptans 'Stairway to Heaven': This variety exhibits blue flowers on variegated foliage that blushes pink in cool weather.
Polemonium Reptans vs. P. Caeruleum
A closely related plant is Pelamonium reptans, a native wildflower of eastern North America. It has a similar appearance to P. caeruleum, but it is somewhat shorter and even more tolerant of cool conditions. It is a short-lived perennial, however, often behaving as a biennial. The native species is rarely planted in gardens, but there are some good cultivated varieties available, including 'Blue Pearl' and 'Brise d'Anjou'. Despite the name, this plant does not spread by creeping rhizomes, but it spreads readily by self-seeding.
In general, Jacob's ladder requires minimal maintenance. If the foliage starts to look tattered, it can also be cut back and cleaned up. New growth will replace the trimmed foliage.
Propagating Jacob's Ladder
Jacob's ladder propagates easily by being divided. Mature Jacob's ladder plants should be divided every three to four years, or they will start to die out in the center. They divide most easily and successfully in early spring. Here's how:
- Locate the plant to separate and carefully unearth the clump so you can see to divide it into two sections.
- Gently pull apart the roots to separate them into sections, but you might find you have to slice through the clump with a spade.
- Replant each section in the desired and proper growing site, and water just enough to moisten the soil.
- When planting a divided section from a mature plant in your garden, place Jacob's ladder at approximately the same depth as it was previously (the same rules apply if planting from a container from the nursery).
How to Grow Jacob's Ladder From Seed
If you already have a Greek valerian plant, it will self-seed on its own from seeds dropped from flower heads. You can also collect the seeds to replant elsewhere. Jacob's ladder can be direct seeded in either spring or fall. Loosely cover the seed with soil, then water. Keep the soil moist, and be sure to mark the spot so that you do not disturb it.
To start seed indoors, sow two months before your last frost date if you want to transplant in spring, or sow in mid-summer if you want to transplant in the fall. The seeds take up to a month to germinate and should be kept moist until then. Transplant outdoors in spring just before your last frost date, or in early to mid-fall.
Prepare this plant for winter by cutting it down completely in the fall after the first frost. After cutting it, place a thin layer of compost over the roots as this will help make the soil nutrient-rich, preparing it for the spring.
Common Pests & Plant Diseases
Jacob's ladder plants are generally problem-free, but there are a few pests and diseases that will attack, particularly if the plants are stressed. These potential problems include:
- Leafminers: Control leafminers by removing affected leaves and/or by treating them with neem oil.
- Slugs: Eliminate slugs with various homespun methods (such as tuna cans or eggshells) or apply an organic treatment (such as diatomaceous earth or a natural commercial repellent).
- Leaf spot: Prevent leaf spot by pruning to ensure good air circulation and watering in the morning so the foliage dries during the day.
- Powdery mildew: Control powdery mildew by keeping the foliage dry (water the ground, not the leaves), pruning for good air circulation, removing affected leaves (as practical), and applying a fungicide as needed.
How to Get Jacob's Ladder to Bloom
Jacob's ladder blooms mainly in the mid-spring and early summer months, from April to May. The foliage stays green all summer, and there is potential for a few repeat blooms in the late summer months of August or September.
What Does Jacob's Ladder's Flowers Look and Smell Like?
Most varieties of Jacob's ladder flowers come in shades of purple and lavender, but there are also white, pink, and yellow varieties available, and all attract common pollinators, such as butterflies, bees, and hummingbirds. The bright blue or purple varieties are among the most popular, blooming in clear tones offset by yellow centers. Many people liken the smell of the blue-colored flowers to that of a grape.
How to Encourage More Blooms
Keep the soil moist, not soaked, to help lengthen the flowering time of Jacob's ladder. Once the flowers finish blooming, cut the flower stalks back to the plant's base to encourage repeat blooms.
Deadheading Jacob's Ladder's Flowers
Extend the flowering of these delicate fragrant flowers and get a second blooming period deadheading any spent flowers from the first bloom.
Common Problems With Jacob's Ladder
This can be a slightly temperamental garden plant, reacting badly to soil that is too dry or too wet, or to an area that gets too much sunlight. Insufficient water and sun scorch can cause the foliage, or just the leaf tips, to start browning.
Does Jacob's ladder plant spread?
These plants will very easily self-seed and spread in an uncontrolled (but not invasive) fashion in the garden unless the spent flowers are removed before the seeds can fall.
Do Jacob's ladder plants come back every year?
Polemonium caeruleum is a long-lived perennial in the right conditions and if it is fed properly.
Does Jacob's ladder plant like sun or shade?
The delicate foliage and the fluorescent color of the flowers make Jacob's ladder a favorite for richly shaded moist areas that receive a minimum of dappled sunlight.
Polemonium caeruleum. Missouri Botanical Garden.
Rooney-Latham, S. & Bischoff, Joseph. First Report of Powdery Mildew Caused by Podosphaera euphorbiae-hirtae on Euphorbia tithymaloides in California. Plant Disease. 96. 1822, 2012. doi:10.1094/PDIS-05-12-0461-PDN