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How to grow Jacob's ladder or Polemonium

Jacobs' Ladder or Polemonium flowers attract butterflies and bees in shady areas.
Jacobs' Ladder or Polemonium flowers attract butterflies and bees in shady areas.
Kim Willis

Jacob’s Ladder or Polemonium (Pronounced: po-lee-MOE-nee-um ) is not seen as often in the garden as it should be. Jacobs Ladder is a hardy, perennial, easy to grow plant that thrives in woodland or partly shaded gardens. Its fern-like foliage contrasts nicely with hosta, heuchera, columbine, astilbe, corydalis and other shade loving plants even when its pretty blue flowers are gone. Other common names for the plant include Greek Valerian and Devils Backbone.

There are many native species of Polemonium spread across the cooler areas of the world and only a few are being used as ornamentals, with two species Polemonium reptans and Polemonium caeruleum dominating the garden scene. It is a shame that other species aren’t being utilized more often as there are many interesting members in the genus. Sometimes native species are sold in catalogs but it can be hard to find the more unusual species.

Polemonium has leaves divided into leaflets, which decrease in size as they proceed to the tip, giving it the common name, Jacobs Ladder. Leaves range from a purplish tinge to bright green and there are at least two varieties with pretty variegated leaves. The plant slowly grows into a large mound from 12- 18 inches high depending on variety and growing conditions. Foliage dies to the ground each winter.

Polemonium flowers are produced in clusters on tall stems from the center of the foliage in early summer. The flowers of the most common species have 5 petals and are about a ½ inch in diameter. There is a cluster of yellow stamens in the center, sometimes red tipped. There are species of Polemonium with double flowers and also with trumpet shaped flowers. Most Polemoniums have blue or purple flowers but white “sports” have been developed and are sometimes offered in garden catalogs. One native species has pale yellow trumpet shaped flowers (Polemonium pauciflorum). Pink flowers are rarely seen. One variety of Jacob’s Ladder, ‘Apricot Delight’ is said to be blue with a peach colored center.

Most Jacob’s Ladder flowers are mildly fragrant if the fragrance can be determined at all. One variety offered in catalogs ‘Snow and Sapphires’ is often described as fragrant but that is a debatable term. Polemonium flowers are appealing to bees and butterflies however, and at least one species of moth in North America, Coleophora polemoniella, uses the plant to feed its larvae.

Other varieties of Polemonium

There are a few cultivars or named varieties of Polemonium commonly offered in garden stores and catalogs. ‘Snow and Sapphires’, mentioned above, has green foliage tipped in snowy white and tall stalks of sky-blue flowers. Another variegated foliage Polemonium is ‘Stairway to Heaven’. It has white variegated leaves that are flushed with pink in cool weather and lavender blue flowers. ‘Touch of Class’ is a newer white variegated foliage Polemonium with medium blue flowers.

White flowered Polemoniums include ‘Album’ and White Pearl.’ ‘Purple Rain’ has purple tinted foliage and deep purple flowers. A hard to find variety of Polemonium pauciflorum called ‘Sulfur Trumpets’ has silver-green foliage and pale yellow trumpet shaped flowers.

Caring for Polemonium

Polemonium is hardy in plant zones 3-7. Polemonium likes rich, humus laden soil in a partially shaded or dappled shade environment. It will survive deeper shade but won’t bloom well there. When it is happy it makes large attractive clumps over several years. Flowers do produce abundant seed and the plant can seed itself in the garden but is rarely invasive enough to be a pest. Cutting the flower stalks off after blooming stops will stop reseeding and makes the plant more attractive.

Polemonium should be watered when the soil becomes dry and they do not do well in dry shade. A light application of slow release flower fertilizer in early spring makes for larger, more vibrant clumps. Avoid too much fertilization as this makes flower stalks floppy and the foliage more sprawling. Too much sun or dry conditions will cause the foliage to tip burn, curl and look unattractive.

Polemonium foliage is attractive to some cats just as catnip is. This is more apparent when plants are bruised or cut. Cats will sometimes damage plants by rolling on them or eating them. Some gardeners never have a problem with cats and it may be that individual plants vary in their attractiveness to cats. Polemonium is also eaten by rabbits and deer. Other than those pests Polemonium has few disease or insect problems to worry about.

Clumps of Jacob’s Ladder do not need to be divided but if you want to increase the plant you can dig and divide the clump in late summer. Promptly replant the divisions and keep them watered.

Other uses of Polemonium

In earlier days Polemonium had some herbal uses but no modern herbal lists them as useful. A black dye can be produced by boiling the plant in olive oil and this is sometimes used to darken and condition hair.

Polemonium is a wonderful plant to attract bees and butterflies to shady areas. The foliage provides interest and useful texture contrast to shaded gardens or even containers. Polemonium naturalizes in woodland gardens and will give years of enjoyment. Plant it along paths and in front of borders so you can enjoy the sight and possibly the smell of its pretty blue flowers.

Here are some additional articles you may want to read.

How to grow trout lilies in the garden

How to prune spring flowering shrubs

Home garden remedies that don’t work

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