Jacob's Ladder Plant (Polemonium Caeruleum) Care Guide - Growing Info + Tips

by Max - last update on December 2, 2019, 4:46 am
Polemonium caeruleum

Jacob’s ladder plant is so-called because of the pinnate leaf pattern, which resembles a ladder. Its delicate foliage is just as attractive as the cup-shaped flowers that bloom in mid to late spring and throughout the summer.

The flowers appear in clusters on top of tall stems, most commonly in shades of blue and purple, though some varieties produce white, yellow, or pink blooms. This plant is a hardy perennial that thrives in partial shade, making it a great way of adding color and vibrancy to corners of gardens that would otherwise be dark and dull. Jacob’s ladder is low-maintenance, provided it is grown in its preferred conditions and is therefore popular among beginner gardeners and those who favor easy-care plants.

Jacob’s Ladder Plant Overview

Quick Facts

Origin Europe
Scientific Name Polemonium caeruleum
Family Polemoniaceae
Type Perennial flowering plant
Common Names Jacob’s ladder plant, Greek valerian, American great valerian
Height Up to 24 inches
Toxicity Non-toxic
Light Full to partial shade
Watering Maintain moist soil
Pests Slugs

 

Varieties

There are two species of plants that are referred to as Jacob’s ladder plants; these are Polemonium caeruleum and Polemonium reptans. Polemonium caeruleum is native to woodlands in temperate regions of Europe and has been cultivated for use in gardens across the US. It is this Jacob’s ladder plant that is commonly found in nurseries and home gardens. It is rare to find this plant growing naturally in the wild.

Meanwhile, Polemonium reptans is natively found in the northeast US and is a threatened plant species. As a means of ensuring this plant's survival, transplanting wild specimens of this plant to home gardens is heavily discouraged. It is also not beneficial for the gardener to do so, as this species has a tendency to get very leggy and does not make a good garden plant.

Within the Polemonium caeruleum species, several varieties exist, including the following.

Bressingham Purple

Polemonium 'Bressingham Purple'
Polemonium 'Bressingham Purple' - Credit to je_wyer

This Jacob’s ladder variety is a shade lover. It has variegated foliage in green with splashes of purple.

Stairway to Heaven

Stairway to Heaven

Another variegated Jacob’s ladder, this plant produces milky cream foliage.

Caring for Your Jacob’s Ladder Plant

Polemonium caeruleum caring

Watering

Jacob's ladder likes to be kept in consistently moist soil, though it does not like soggy conditions. For this reason, ensuring you have well-draining soil is key, as it will prevent the soil from becoming waterlogged in the event of overwatering, which will protect against root rot.

One of the most important things to know about watering this plant is that it doesn’t like inconsistency. It won’t react well to sporadic watering where it is moist some weeks and dry on other weeks. Instead, work to ensure you water your Jacob’s ladder with consistency. The frequency with which you should water this plant will depend on the light it receives. If in a position of full shade, the water will evaporate from the soil much more slowly than those planted in partial shade, and therefore will need to be watered less frequently.

Aim for evenly moist soil around the plant, only offering more water when the top layer of the soil has started to dry out, as this will prevent the soil from becoming too wet. Once the plant is well-established and has a strong root system, it can adapt to become drought tolerant. However, it would still prefer to be kept in moist soil.

Ensuring the plant has enough moisture during its growing season will result in more flowers and a longer blooming period. Jacob’s ladder can have problems with fungal leaf spot and powdery mildew, which typically occur when the environment is too humid, and moisture sits on the foliage of the plant.

As the plant generally grows in the shade, water will not evaporate quickly from the foliage as it would if kept in the sun, making ideal conditions for fungal disease to thrive. To help avoid this problem, always water the plant at soil level to prevent the leaves from getting wet and succumbing to fungal disease (Royal Horticultural Society).

Light

Polemonium caeruleum in the light

This plant grows best in partial shade or dappled shade. Ideally, plant it under the canopy of a tree with branches that aren’t too dense, allowing for dappled sunlight to come through and reach the Jabob’s ladder plant. Alternatively, you could grow this plant in a shady corner or in a spot that receives a few hours of morning sunlight but is shaded by a fence or building in the afternoon.

The reason this plant likes shade is that too much sun or heat will scorch the foliage. However, the plant doesn’t like to be in full shade as it requires some sun for the production of its flowers. This means partial shade is best, striking a good balance with some shade and some sun.

There are varieties of the plant that will cope with sunlight better than others. Generally speaking, the plants with dark green foliage fare better in direct sunlight, while the varieties with variegated leaves are more sensitive to sunlight and will require more shaded protection. The climate you are growing the plant in will also affect the amount of light it can handle; Jacob’s ladder growing in warmer regions will need a higher proportion of shade throughout the day than those grown in cooler climates.

Temperature

Polemonium caeruleum grows best in USDA hardiness zones 3 to 8
Polemonium caeruleum grows best in USDA hardiness zones 3 to 8

Jacob’s ladder is a hardy plant that does well in a wide range of climates. It will grow best in USDA hardiness zones 3 to 8, but it can also be grown anywhere up to zone 12, though care requirements will vary slightly depending on your climate.

If grown in zones 8 to 10, Jacob’s ladder will need to be grown in almost full shade. This will result in fewer flowers than those plants grown in dappled shade, but it will help to keep the plant cool. Jacob’s ladder does not like to get too hot, and therefore relies on the shade to lower the temperature by a few degrees and keep the plant happy.

If the plant gets too hot, it can wilt and die, while too much sun exposure will scorch the foliage. In cooler climates, the plant will act as an annual rather than a perennial. If you grow the plant in zones lower than zone 6, you can expect the plant to die off in the winter, but new plants will appear the following spring, where the previous plant self-seeded.

Propagation

There are several ways to grow new Jacob’s ladder plant, including planting from seed, division, and stem cuttings.

The plant is a prolific self-seeder, so if you are happy for new Jacob’s ladder plants to appear each year, then all you need to do is refrain from deadheading the spent flowers. Spent flowers that are left alone will develop and drop seeds, which will then provide new plants the following spring.

To prevent an overwhelming amount of new plants, you should deadhead most of the spent flowers but leave a few intact. If too many flowers do appear, you can simply thin them out to allow growing room. If you would prefer not to allow the plant to re-seed, you just need to deadhead all spent flowers.

You can also grow this plant from seed yourself, either directly in the ground, or get a head start by sowing the seeds indoors a few weeks before the final frost is expected. To sow the seeds outside, sprinkle them on moist soil after the last frost, and lightly cover with more soil.

Maintain moist soil, and once seedlings appear, they can be thinned out to around 18 inches between each new plant. The sow the seeds inside, follow the same process using a seed tray a few weeks earlier, and then transplant the seedlings outside once the risk of frost has passed.

The division is also a good method of propagating Jacob’s ladder. Once a plant has reached maturity, carefully dig it up and tease the roots apart, separating the plant into two. Tangled roots can be cut with sharp scissors, but take care to keep as many of the roots intact as possible. Once separated, plant the two Jacob’s ladders back into the ground.

It is possible to propagate this plant from stem cuttings, but this is not commonly done as the success rate for this is quite low.

Pruning

Jacob’s ladder plants are great for beginner gardeners as they are very low-maintenance. No pruning of this plant is necessary at all for the health of the plant; however, if you wish, you can prune it occasionally to keep a neat look. Leggy stems can be cut back to maintain a uniform shape, and some of the stems can be thinned out to encourage airflow if the fungal disease is a problem.

 If the plant dies back in winter, you can cut away the brown stems to make space for the new growth that will appear the following spring. Deadheading is also a pruning method you can use to encourage more blooms and a longer flowering period. To deadhead, this plant, cut stems right back to the base once the flower is spent (University of Wisconsin-Madison Extension).

If you have any questions about Jacob’s ladder plants, leave a comment below, and please share this page with other plant growers!

Jacob's Ladder Plant (Polemonium Caeruleum) Care Guide - Growing Info + Tips

Add new comment

The content of this field is kept private and will not be shown publicly.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Back to top