CPC Plant Profile: Western Jacob's-ladder
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Plant Profile

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

An herbarium sheet from the Chicago Botanic Garden. Photo Credit: Chicago Botanic Garden
  • Global Rank: T2 - Imperiled
  • Legal Status: N/A
  • Family: Polemoniaceae
  • State: MN, WI
  • Nature Serve ID: 145794
  • Date Inducted in National Collection: 10/17/2021

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.

Participating Institutions
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
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

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.

Ecological Relationships

The ecological relationship between Polemonium and other species is virtually unknown.

Common Name Name in Text Association Type Source InteractionID

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