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Kevin Doyle

Buttonweed (Diodia teres var. teres)

Life history

Species overview

Buttonweed (Diodia teres var. teres), a State Special Concern plant, is found on sandy terraces along the Wisconsin River. Blooming occurs early July through early September; fruiting occurs early August through late October. The optimal identification period for this species is late June through late October.

Synonyms: Diodia teres, Diodia teres var. setifera


  • Distinguishing characteristics: Fruit much surpassed by the long (6 to 10 mm) stipules.
  • Flower characteristics: Sessile in many of the upper axils; sepals 4, lanceolate; corolla funnel-form, white to pink or pale purple.
  • Fruit characteristics: Obovoid, finely pubescent or short-hirsute, crowned by the persistent sepals.
  • Leaf characteristics: Stiff, sessile, linear to narrowly lanceolate, scabrous, aristate at apex, rounded or narrowed at base.


  • Blooming phenology: early July through early September
  • Fruiting phenology: early August through late October
  • Optimum time to identify: late June through late October


  • Growth form: Forb-erect
  • Vegetative reproduction:
  • Life cycle: Annual
  • Comments: Associated Species: Aristida tuberculosa, Polygonella articulata, Hypericum gentianoides, Strophostyles helveola, Cassia fasciculata, Sporobolus heterolepis, Polygonum tenue.

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 Buttonweed (Diodia teres var. teres). 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 Diodia teres var. teres in the Natural Heritage Inventory Database as of March 2012.

Summary Information
State StatusSC
Federal Status in Wisconsinnone
State RankS1
Global RankG5T5
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 on sandy terraces along the Wisconsin River.
  • Soils: Dry or sandy soils.

Natural communities

This table lists the natural communities that are associated with Buttonweed. 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
Sand Prairie 3

Ecological landscapes

This table lists the ecological landscape association scores for Buttonweed. 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.

Buttonweed (Diodia teres var. teres) has very few known occurrences in the state and is of the highest priority for conservation; we encourage you to consult with your District Ecologist or NHI Botanist for specific recommendations for your site.

Avoidance measures

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

  • 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.
  • Avoid broadcast spraying of herbicides; use care with spot spraying.
  • Avoid locating landings, staging areas, or access routes in open sandy areas dominated by native grasses.

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.
  • Prescribed burns and/or brushing may be beneficial (dependent on local site conditions).


Buttonweed  [Photo #23473]

Photo © Robert H. Read.

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: Tuesday, October 07, 2014
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