Western Jacob's Ladder
Polemonium occidentale Greene spp. lacustre Wherry
Not in the Garden
Late Spring to Early Summer Flowering
The Polemonium genus covers a large number of plants commonly known as "Jacob's Ladder."
Western Jacob's Ladder is a native perennial forb growing almost 30 inches high on slender upright stems that are light green.
The leaves on the flowering stem are alternate and pinnately-divided into 9 to 13 oblong leaflets. A terminal leaflet creates the odd number of leaflets. Leaflets are dark green in color, with smooth edges, usually no hair on the upper surface, and usually not stalked. The upper stem leaves have fewer leaflets. Most leaves emerge directly from the rhizome and are on long stalks with more leaflets.
The inflorescence is a branched thrysoid panicle arising at the top of the stems and held high above the leaves.
The flowers are bell shaped with 5 blue-violet petals that spread displaying a more color at the base of the petals with dark nectar guides. The calyx is green with reddish tints and with fine hair. Its five lobes are lance shaped. There are five stamens with whitish filaments and pale yellow anthers. There not as long as the style but extend to the corolla throat. The single style is longer, exserted and has a 3-parted stigma.
Seed: Fertile flowers produce a dry 3-chambered seed capsule.
Habitat: Western Jacob's Ladder is found in open wetland forest with a ground surface dominated by mosses and a neutral pH. Unlike P. reptans, good flower bloom requires sunlight to reach the surface. It grows from a shallow creeping rhizome. Only six sites are known, four in northern Minnesota and two in northern Wisconsin.
Names: The genus name Polemonium is a bit obscure but according to Stern (Ref. #37a) comes from the Greek pŏlĕmōniŏn which referred to an old medicinal plant thought to have a connection back to the Greek philosopher Polemon of Cappadocia. The species name, occidentale, means "western" and refers to this being a new world species. "Lacustre" is a word referring to "of the lakes" and in this case to the moist wetlands where the plant grows. The name 'Jacob's Ladder' is an old biblical reference to the leaflets forming 'a ladder to heaven.'.
The author name for the plant classification - ‘Greene’ - is for Edward Lee Greene (1843-1915), American botanist who wrote Landmarks of Botanical History, named or redescribed over 4,400 species of plants in the American west and was the first Professor of Botany at the University of California. ‘Wherry’ refers to Edgar T. Wherry (1885-1982) American soil scientist and botanist, who is primarily known for his field work on ferns.
Comparisons: Several species are similar to P. occidentale. P. reptans [photo below] which has less bright flowers with stamens shorter than the petals which are not as wide and less spreading. It has wider leaflets and more of them on the flowering stem. A garden variety of Jacob's Ladder with blue flowers is sometimes sold with the scientific name P. caeruleum and is not a native species.
See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.
Above: The inflorescence is a branched panicle with each branch have just a few flowers. Drawing by Ellen Fuge, courtesy Minnesota DNR and Nancy Sather.
Below: 1st photo - Flower petals are open and spreading with hairy stalks. 2nd photo - The stamens have white filaments, yellow anthers, shorter than the single style which has a three-parted sigma.
Below - comparison: Spreading Jacobs Ladder - The corolla is bell shaped with 5 petals. The five stamens have whitish filaments and light yellow anthers. There is a single style with a 3-lobed tip.
Below: The basal and ground leaves of Western Jacob's Ladder.
Below: 1st photo - maturing seed capsules. 2nd photo - a smaller flowering stem leaf.
Notes: There are two species of Polemonium native to Minnesota - P. occidentale subsp. lacustre, Western Jacob's Ladder and P. reptans, Spreading Jacob's Ladder. The first is rare, endangered, and occurs only in four locations in the coniferous forests of northern Minnesota and two in Wisconsin, making up the entire known population of the subspecies in North America. The other is more common, being found in SE Minnesota and in most of the eastern half of the United States.
The first populations of this species were found in 1944 by Olga Lakela, then curator of the University of Minnesota at Duluth Herbarium, but were discounted by many as the site could never be found by others, but in 1982 a population was found in Wisconsin and in 1988 in Minnesota, close to the original 1944 described location.
A second subspecies, ssp occidentale is found in the western United States and Canada.
The University of Minnesota Landscape Arboretum has a native plant conservation program which has banked species of Western Jacob's Ladder from three of the known locations and has grown them at the Arboretum. The photos on this page are from the collection at the Arboretum.
References and site links
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"