The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Glossostigma cleistanthum
Glossostigma cleistanthum

Copyright Info
Glossostigma cleistanthum W.R. Barker

Common name: mudmats

Synonyms and Other Names: originally misidentified as Glossostigma diandrum

Taxonomy: available through www.itis.govITIS logo

Identification: Glossostigma cleistanthum is characterized as unusual, bright green patches developing on muddy substrates of littoral zones in full sun.  It's tiny leaves arise from creeping stems that grow horizontally just below the soil surface and root along the nodes.  Leaves are paired and spatulate-shaped (having linear bases with broadened tips). 

Plants are found both submerged and emergent.  Where growing submerged, leaves of G. cleistanthum range between 07-5.7 cm long and bear closed, self-fertilizing flowers, called cleistogams that are nearly sessile (Les et al. 2006).  Where the water recedes in summer months, leaves are much smaller (0.5 - 1.1 cm long) and produce insect pollinated chasmogamous flowers (Les et al. 2006) borne on short stalks. Seeds, produced in capsules, are present in U.S. populations and probably contribute to the rapid rate of spread once G. cleistanthum is introduced to a waterbody. 

The introduced Glossostigma cleistanthum closely resembles our native Limosella (mudwort) species and may also be confused with emergent leaf forms of some members of Utricularia (bladderwort).

Native Range: Australia and New Zealand (Cook 1996)

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Glossostigma cleistanthum are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CT199220154Outlet Connecticut River; Quinebaug River; Shetucket River; Thames
NJ199120235Crosswicks-Neshaminy; Lower Delaware; Middle Delaware-Musconetcong; Mullica-Toms; Raritan
RI200220221Pawcatuck River

Table last updated 7/21/2024

† Populations may not be currently present.

Ecology: Grows submerged and emerged along sandy to muddy shorelines.  Favors oligotrophic conditions - low pH, alkalinity, conductivity, phosphorous and where water clarity is high, it will grow up to 4 meters deep. 

Means of Introduction: Initial introduction probably by aquarium release; subsequent movement to new waterbodies may occur with migrating geese or other waterfowl.  

Status: Spreading rapidly in the Mid-Atlantic region.  

Impact of Introduction: Once introduced, G. cleistanthum spreads rapidly to cover prime littoral habitat, but because of its small size, it is unlikely to interfere with recreational lake uses.  It is not known as invasive in its native range or elsewhere.  Ecological impacts are unknown, but in some areas, plants reach extremely high densities, with as many as 25,000 plants per square meter, and the lake bottom appears a solid green, monotypic mat.  Numerous imperiled plant species are associated with the same habitat where G. cleistanthum is commonly found (Les et al. 2006)  

Remarks: Previously erroneously identified as Glossostigma diandrum, but molecular analysis has confirmed 14 of the 19 known populations to be G. cleistanthum (Les et al. 2006).  

References: (click for full references)

Les, D. H., R. S. Capers, and N. P. Tippery. 2006. Introduction of Glossostigma (Phrymaceae) to North America: a taxonomic and ecological overview. American Journal of Botany 93(6): 927-939.

Cook, C.D.K. 1996. Aquatic plant book. SPB Academic Publishing b.v., Amsterdam, Netherlands.

Author: Howard Morgan, V.

Revision Date: 8/30/2023

Citation Information:
Howard Morgan, V., 2024, Glossostigma cleistanthum W.R. Barker: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=257, Revision Date: 8/30/2023, Access Date: 7/21/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.


The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [7/21/2024].

Contact us if you are using data from this site for a publication to make sure the data are being used appropriately and for potential co-authorship if warranted.

For general information and questions about the database, contact Wesley Daniel. For problems and technical issues, contact Matthew Neilson.