Taxonomy and Botany of Jacob's Ladder
Plant taxonomy classifies Jacob's ladder plants as Polemonium. A species widely grown is caeruleum.
Characteristics of This Perennial
The height of Jacob's ladder plants will vary considerably, according to the type you grow. The basic Polemonium caeruleum attains a height of about 3 feet (with a narrower spread), with an upright habit.
Flowers are bell-shaped and first appear, depending on the variety that you are growing (and where you live), anywhere from mid-spring to early summer. Besides blue flowers, color choices for Polemonium include lavender, pink, purple and white.
You either love the fern-like leaves or hate them. Some people find them "weedy-looking," but I appreciate the contrast in texture that they provide with a plant like hosta. The foliage first appears in early spring.
Geographical Origin, Planting Zones, Sun and Soil Requirements
Jacob's ladder flowers can be grown in partial shade and are best planted in a well-drained soil enriched with humus. The lower your zone (that is, the colder your climate), the more sun you can allow them. Variegated types (see below) tolerate less sun.
Landscaping Uses, Care Tips
Jacob's ladder flowers work well in a shade garden (with dappled sun) or semi-shady border. They are often grown together with such shade loving plants as hosta, lungwort (Pulmonaria), columbine, bleeding heart, impatiens and Brunnera. In cooler climates, where Jacob's ladder can tolerate more sun, shorter types (see below) will be useful for rock gardens.
Deadhead the flowers to encourage reblooming. These flowers sometimes self-seed; pull up and dispose of the seedlings if you wish to check the spread of Jacob's ladder plants.
Types of Jacob's Ladder
- Polemonium caeruleum 'Album' has white flowers
- Polemonium caeruleum 'Brise d'Anjou' is variegated
Besides caeruleum, other species of Polemonium exist. For example, the species, reptans is native to North America. Although it does not creep, as the species name, reptans would suggest, this type of Jacob's ladder does stay shorter than Polemonium caeruleum. 'Stairway to Heaven' is variegated. Even shorter than reptans is the alpine kind, viscosum.
Origin of Names, "Jacob's Ladder," "Polemonium Caeruleum"
The common name, "Jacob's ladder" derives from the appearance of this perennial's leaves. The leaves are compound, composed of numerous opposite, small, narrow leaflets -- like the rungs on a ladder. But "ladder plant" was, presumably, dismissed in favor of a more colorful name. Instead, the most famous ladder in literature was evoked: Jacob's ladder, a vision Jacob saw in a dream as related in Genesis 28: 12-22: "And he dreamed, and behold a ladder set up on the earth, and the top of it reached to heaven...."
The botanical name, Polemonium caeruleum is another matter. There is much disagreement over the origin of the genus name, Polemonium. The most we can say with certainty is that the name goes back to the Greek and Roman Classical period; it appears, for example, in the Greek author, Disocorides (this .pdf file loads slowly). The species name, caeruleum, is Latin for the most common color for Jacob's ladder flowers: namely, blue. Please view my photo gallery for pictures of other plants with blue flowers.
Another common name for Jacob's ladder is "Greek valerian." True valerian (Valeriana officinalis) is a medicinal herb plant; its root has been used to treat such ailments as sleeping problems. It is only speculation on my part, but perhaps this common name derives from:
- A superficial resemblance between valerian and Jacob's ladder
- Polemonium's roots in the Classical world
Need more choices for shady locations? See my article on the Best Perennials for Shade.