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Smooth Phlox (Phlox glaberrima ssp. interior)

Life history

Species overview

Smooth Phlox (Phlox glaberrima ssp. interior), a Wisconsin Endangered plant, is found in coastal Lake Michigan calcareous prairies. Blooming occurs early June through late July; fruiting occurs early July through early August. The optimal identification period for this species is early June through late July.

Synonyms: Phlox glaberrima var. interior


  • Distinguishing characteristics: Distinguished from other members of the Phlox genus by its stamens and styles which reach at least the mouth of the tube (vs. reaching only half way up tube) and its petals, which are not notched.
  • Flower characteristics: Inflorescence of usually several cymes, terminal and from the upper 1 to 4 pairs of axils; calyx 5 to 10 mm; corolla red-purple, 1.5 to 2 cm wide; stlye elongate.
  • Fruit characteristics: Capsule narrow; seeds many, small.
  • Leaf characteristics: Leaves numerous, firm, spreading, linear to narrowly lanceolate or sometimes even ovate, gradually tapering to a sharp tip, 5 to 15 cm long by 3 to 20 mm wide.


  • Blooming phenology: early June through late July
  • Fruiting phenology: early July through early August
  • Optimum time to identify: The optimal identification period for this species is early June through late July


  • Growth form: Forb-erect
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Tradescantia ohioensis, Spartina pectinata, Allium cernuum, Liatris spicata, Pedicularis canadensis, Dodecatheon meadii, Andropogon scoparius, Sorghastrum nutans, Pycnanthemum flexuosum.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - state and federal - and the rank (S and G Ranks) for Smooth Phlox (Phlox glaberrima ssp. interior). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Documented locations of Phlox glaberrima ssp. interior in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusEND
Federal Status in Wisconsinnone
State RankS2
Global RankG5TNR
Tracked by NHIY

Habitats and landscapes

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

General habitat information

  • Habitat description: Found in coastal Lake Michigan calcareous prairies.
  • Soils: Wet, calcareous soils.

Natural communities

This table lists the natural communities that are associated with Smooth Phlox. Scores for natural community associations are: "significant" association (score=3), "moderate association" (score=2) or the species can be present but is only weakly associated with the community (score=1).

Natural communities score
Wet-mesic Prairie 3
Mesic Prairie 3

Ecological landscapes

This table lists the ecological landscape association scores for Smooth Phlox. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

Species guidance

The Endangered Resources Program has developed avoidance measures and management guidelines for plants on the Natural Heritage Working List. These are a work in progress, and we welcome your suggestions and feedback. Sources used in developing this information can be found here.

Avoidance measures

These are specific actions designed to avoid "take" (mortality) of this species.

  • Avoid broadcast spraying of herbicides; use care with spot spraying.
  • Avoid known individual plant locations and conduct operations elsewhere when they are least likely to cause damage. Ideally, this would involve frozen, snow-covered ground. However, in areas of the state where frozen conditions are unreliable, very dry soils late in the growing season might be the best available alternative. Consult with a biologist, if needed.

Management guidance

Management guidelines are additional considerations that may help maintain or enhance habitat for this species

  • Maintain and restore open habitat through selective clearing and brushing.
  • Minimize disturbance to hydrology, including soil disturbance from rutting.
  • Prescribed burns and/or brushing may be beneficial (dependent on local site conditions).


Smooth Phlox Photo.

Photo © Kitty Kohout.

Smooth Phlox Photo.

Phlox glabberima, at Chiwaukee Prairie SNA, 1987

Photo by Thomas Meyer, Wisconsin DNR.

Smooth Phlox Photo.

Photo © Robert H. Read.

Smooth Phlox Photo.

Photo © Richard Bauer.

Smooth Phlox Photo.

Smooth phlox is restricted in Wisconsin to just a few deep-soil, tallgrass prairie remnants. Kenosha County.

Photo by Thomas Meyer, Wisconsin DNR.

Support for Wisconsin's rare plant information has been provided by the Division of Forestry, the Endangered Resources Fund and the Wisconsin Rare Plant Preservation Fund. To donate, visit the Natural Resources Foundation of Wisconsin [exit DNR].

Last revised: Wednesday, May 05, 2021
Southwest Savanna Southern Lake Michigan Coastal Western Coulees and Ridges Southeast Glacial Plains Central Sand Hills Central Lake Michigan Coastal Central Sand Plains Northern Lake Michigan Coastal Northern Lake Michigan Coastal Northeast Sands Western Prairie North Central Forest Northern Highlands Northwest Lowlands Northwest Sands Northwest Lowlands Superior Coastal Plains Forest Transition