Polemonium

( pol - em - MOH - nee - um )

At-A-Glance Information

This genus of flowering perennials (rarely annuals) includes species commonly called Jacob's Ladders, Greek Valerian, and Charity. These plants need partial to full shade and regular water to perform well in the landscape, and produce ferny foliage and clusters of bell-shaped blue (rarely white or pink) flowers that bloom in spring and summer. They are great candidates for under-tree plantings, as their root systems are not invasive. Most species are native to cool temperate to arctic regions in the Northern Hemisphere and reach between 4 and 48 inches tall when in bloom. Use these plants in woodland gardens, mixed beds and borders, and as underplantings for ornamental trees and shrubs.

Polemonium Species and Varietals

Polemonium is the type genus member of the plant family Polemoniaceae and includes between 25 and 40 distinct species. The plants in this genus are related to those in Phlox, Gilia, and Ipomopsis. Polemonium grows best in USDA hardiness zones 3-8 or Sunset growing zones 1-11 and 14-17, though this varies somewhat depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Polemonium caeruleum (Jacob's Ladder, Greek Valerian, Charity)
This species is native to Europe and Asia, and has a somewhat upright habit, reaching 1-3 feet tall and 1-1.5 feet wide. Flowers are lavender-blue. Variety 'Brise d'Anjou' (pictured) has leaves outlined in white. Other commonly grown garden cultivars include 'Album' (with white flowers), 'Blue Pearl', 'White Pearl' (with white flowers) and 'Snow and Sapphires' (with variegated foliage).

Polemonium californicum (Moving Polemonium, Low Jacob's-Ladder, California Jacob's Ladder)
Native to the northwestern United States, these plants prefer shady, moist habitats like mountain woodland areas. Individual plants form clumps of 12-20 inches. Flowers are typically blue-purple with yellow and white centers, and bloom in compound inflorescences at the tips of stems.

Polemonium carneum (Royal Jacob's Ladder, Great Polemonium, Oregon Polemonium, Salmon Polemonium)
This species is native to Washington and California, and reaches 1-1.5 feet tall and about as wide at maturity. Flower buds are yellow, and open to reveal peach-pink blossoms that mature to a purplish-blue color. Green foliage is divided and ferny. The main cultivar of this species is 'Apricot Delight', with soft pale pink bowl-shaped flowers flushed with apricot and yellow at their centers.

Polemonium eximium (Skypilot, Showy Sky Pilot)
This perennial species grows at high altitudes, and is endemic to the Sierra Nevada mountain range in California. It grows well in USDA hardiness zones 1-3, and is a very sought-after wildflower, producing a 4-16 inch tall plant with sticky, aromatic foliage. Fragrant flowers are dark blue, sometimes light blue or pink-lavender. They are somewhat unpleasant smelling; their urine-like fragrance attracts their best pollinators.

Polemonium pulcherrimum (Beautiful Jacob's Ladder, Showy Jacob's Ladder, Skunk-Leaved Polemonium)
This species grows well in USDA hardiness zones 4-8 or Sunset growing zones A1-A3, 1-11, 14-17 and H1 and is native from Alaska down through northern California. It can be either sprawling or erect, growing to a foot tall and just as wide. Flowers bloom in clusters of blue or white, and often have yellow throats. Great for shady, rocky areas of the garden. Foliage smells like a skunk.

Polemonium reptans (Spreading Jacob's Ladder, Creeping Jacob's Ladder, False Jacob's Ladder, Abscess Root, American Greek Valerian, Blue Bells, Stairway to Heaven, Sweatroot)
This species is native to eastern areas of the United States and grows to 1-1.5 feet tall and a foot wide. Flowers are light blue. Cultivars include 'Blue Pearl' (10 inches tall and 1.5 feet wide with bright blue flowers) and 'Firmament' (20 inches tall and a foot wide with bright blue flowers).

Polemonium vanbruntiae (Appalachian Jacob's Ladder, Bog Jacob's Ladder, Vanbrunt's Polemonium)
These perennial plants have green foliage and produce purple flowers from the middle of June to late July. They prefer to grow in wetland-type landscapes such as bogs, swamps, and marshes. Appalachian Jacob's Ladder grows well in USDA hardiness zones 3-7.

Caring for Polemonium

Grow Jacob's Ladder plants in full sun; ideally these plants should be getting between 6 and 8 hours of direct sun each day. They can also grow in dappled shade, but will not flower as profusely. In areas with particularly hot climates, make sure these flowers get some afternoon shade when temperatures are at their peak (typically between 2 and 3 PM). These flowers appreciate a well-draining soil that can hold a good amount of water. They grow best in soils that are relatively fertile with a pH of between 6.0 and 7.5 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, these plants need consistently moist soil to perform well, and do not like to have dry feet. Water regularly to maintain medium moisture levels, but make sure that soil is not becoming soggy, which can cause issues with root rot and other fungal diseases.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants require minimal pruning; simply remove dead, damaged, or diseased foliage at any time, and deadhead spent flower spikes as they appear to neaten the appearance of plants and discourage free re-seeding in the garden bed. Polemonium will very easily spread in the garden in an uncontrolled, but not necessarily invasive, manner unless spent flower stems are removed before seeds can form. Cut plants down completely after they are damaged by the first frost of the year. Mulch over the top of the plants to insulate further. Plants will regrow each spring. Every few years, Polemonium plants will need to be divided; for instructions on how to divide Polemonium, see the Propagation section below. These plants can thrive for 3 to 5 years or so in the garden before needing to be replaced, but will form clumps over time that can survive indefinitely.

Propagation

Polemonium can be propagated either by division or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the division method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Jacob's Ladder, follow the instructions below:

Propagating Polemonium by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seed heads on plants are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will continue to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
In either late winter or early springtime, get your container prepared. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes around 4 weeks from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 65 and 72 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Propagating Polemonium by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil, compost and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring (after the plant has entered dormancy, but before it has begun its new spring growth), and needs to be done every few years regardless of whether you have the goal of propagating the plants for best performance. To propagate by division, follow these steps:

Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the root(s). Once you have worked it up out of the ground, lay it out.
Start to tease apart the roots with your fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick root section attached.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divisions and water thoroughly.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout in the next growing season.