Common name: mudmats
Synonyms and Other Names: originally misidentified as Glossostigma diandrum
available through www.itis.gov
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
Puerto Rico &
Interactive maps: Point Distribution Maps
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.
Table last updated 9/17/2021
† 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)
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.
Howard Morgan, V.
Revision Date: 2/9/2009
Howard Morgan, V., 2021, 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: 2/9/2009, Access Date: 9/18/2021
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.