Western Jacob's-ladder / Center For Plant Conservation
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Plant Profile

Western Jacob's-ladder (Polemonium occidentale ssp. lacustre)

Polemonium occidentale ssp. lacustre flowering in situ. Peak time to find this species flowering is in early July.

Photo Credit: University of Minnesota Landscape Arboretum
  • Global Rank: T2 - Imperiled
  • Legal Status: N/A
  • Family: Polemoniaceae
  • State: MN, WI
  • Nature Serve ID: 145794
  • Lifeform: Forb/herb
  • Date Inducted in National Collection:

Polemonium occidentale var. lacustre is the extremely rare Midwestern variety of a more common western species that is found in Minnesota and Wisconsin. The name \\\"lacustre\\\" refers to the fact that this subspecies is found only in wetland habitat. This single stemmed phlox produces bright violet flowers in late June or early July. In general, Polemonium species are easily recognized by their ladder-like leaf structure. This rare subspecies can reproduce vegetatively as well as through seed production.

Where is Western Jacob's-ladder (Polemonium occidentale ssp. lacustre) located in the wild?


Anderson and colleagues (1998) describe Polemonium as generally being found in wet peat bogs with a blanket of sphagnum and other mosses. Typical woods species in this habitat include a mixture of white cedar, black spruce and tamarack. Characteristic understory species include speckled alder, dwarf birch and willow. This Polemonium species is also associated with other rare taxa such as marsh valerian and sparse-flowered sedge.


Polemonium occidentale var. lacustre is found in Wisconsin and Minnesota.

States & Provinces:

Western Jacob's-ladder can be found in Minnesota, Wisconsin

Which CPC Partners conserve Western Jacob's-ladder (Polemonium occidentale ssp. lacustre)?

CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.

Conservation Actions

David Remucal
  • 05/01/2023

Jeffrey Rose has published genetic work and analysis from his dissertation which indicates Polemonium occidentale ssp. lacustre should be treated as its own species, and not a subspecies. In the paper they propose calling it Polemonium lacustre - elevating it to an important endemic to the upper Great Lakes region. This elevation in status will be very important to elevating the legal status of the species to potentially gain federal protection.


Jeffrey P. Rose, Kenneth J. Sytsma "A New Combination for a Narrowly Endemic Polemonium (Polemoniaceae)," Novon: A Journal for Botanical Nomenclature, 31(1), 33-35, (22 March 2023)

David Remucal
  • 04/29/2022
  • Seed Collection

For the CPC RNA longevity study, the population called "Alborn 30" was revisited in 2021 and seed was collected. This population may be the most robust and stable population of all known locations for this species. It isn't the largest, but it is very productive and the testing we've done with seed from the known sites have shown that they typically produce the highest percentage of viable seed by a fair bit. This species seems to need regular disturbance for successful maintenance of a population. When in an open canopy it flowers, but when in closed canopy it reproduces vegetatively. Seed recruitment is likely needed to maintain genetic variability in a population, but vegetative recruitment may be how individual genetic lines last more than a few years. There is still a lot to learn about this plant and its environmental needs and interactions but this site appears to have a regular flood disturbance that periodically pushes back the canopy, creating a "pump" that allows for both vegetative and sexual reproduction in the same area.

Center for Plant Conservation
  • 08/19/2021
  • Orthodox Seed Banking

In 2021, CPC contracted University of Minnesota Landscape Arboretum to recollect seed from a population currently held in long term orthodox seed storage as part of an IMLS-funded seed longevity experiment. The National Laboratory for Genetic Resources Preservation will evaluate how germination tested viability and RNA Integrity of seed lots decline over time in storage.

  • 09/23/2020
  • Genetic Research

Genetic analysis (using isozyme and RAPD DNA markers) indicates that Polemonium occidentale var. lacustre has had an evolutionary history that is genetically isolated from other Polemonium species. This study also indicated that there is little genetic differentiation between populations of this species. (Cole 1998)

  • 09/23/2020
  • Orthodox Seed Banking

Seeds have been seed banked, and will need continued management

Nature Serve Biotics
  • 05/02/2017

Only 6 extant populations in the Great Lakes Region (St. Louis and Itasca Counties in Minnesota and Florence County in Wisconsin). Although a great deal of potential habitat exists and known populations are viable with potentially 1,000's plants, number of individual genets is not known and extensive surveys have not turned up more locations. Further research into the life history and biology including pollinators and seed dispersal mechanisms may explain what is limiting the expansion of this species.??Information on total population size and phylogenetic relationships to other members of the genus as well as response to climate change may change the status.

Andrea Tietmeyer
  • 01/01/2010

Canopy Closure Any activity that directly alters the habitat and destroys plants, including peat mining and flooding by beaver dams. (Anderson et al. 1998)

Andrea Tietmeyer
  • 01/01/2010

There are five known populations of this taxon; three are located in St. Louis County in Minnesota and two are located in Florence County in Wisconsin. It is difficult to estimate the number of individuals, as population size fluctuates from year to year. (Anderson et al. 1998)

Andrea Tietmeyer
  • 01/01/2010

Genetic analysis (using isozyme and RAPD DNA markers) indicates that Polemonium occidentale var. lacustre has had an evolutionary history that is genetically isolated from other Polemonium species. This study also indicated that there is little genetic differentiation between populations of this species. (Cole 1998)

Andrea Tietmeyer
  • 01/01/2010

Polemonium occidentale var. lacustre is listed as endangered in both Minnesota and Wisconsin. All five populations are located either on county, state, or federal land, which have all been or are currently being managed for timber production. Observations of these five populations before and after logging activities suggest that logging is not detrimental to the species as long as the plants themselves are not directly impacted (i.e.. slash is not piled on the plants, the area of the population is not excavated, and the hydrological regime is not altered as a secondary effect of logging). In fact, it appears that this taxon needs natural or artificial canopy openings in order to stimulate flower production and assure seed production. (Anderson et al. 1998) This species is not currently under federal protection. Although the species was placed under review by the U.S. Fish and Wildlife Service in 1976 (as Federal Category 2), no formal action was taken and the Category 2 status was disbanded. A 1998 report (Anderson et al.) state that further genetic studies need to be carried out to confirm without a doubt that there is a genetic basis in addition to the morphological basis for treating this taxon as a distinct subspecies.

Andrea Tietmeyer
  • 01/01/2010

The evolutionary relationship of this variety to other members of its genus is still largely unknown (Anderson et al 1998). Further work is also needed to clarify its taxonomic status. It appears as though a management plan that can maintain an open canopy is necessary for seed production (Anderson et al. 1998). However, further research and monitoring is needed to determine the optimum conditions required to maintain healthy populations. Other threats, natural and anthropogenic, need to be determined. Surveys of areas in the upper peninsula of Michigan with similar habitat conditions are also needed, as they may uncover additional populations.

Andrea Tietmeyer
  • 01/01/2010

There have been no known attempts to propagate this species off-site. Seeds have been seed banked, and will need continued management.


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Taxon Polemonium occidentale ssp. lacustre
Authority Wherry
Family Polemoniaceae
CPC Number 3557
ITIS 524547
Duration Perennial
Common Names Jacob's ladder
Associated Scientific Names Polemonium occidentale var. lacustre | Polemonium occidentale ssp. lacustre
Distribution Polemonium occidentale var. lacustre is found in Wisconsin and Minnesota.
State Rank
State State Rank
Minnesota S1
Wisconsin S1
Ecological Relationships


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