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Mudmat (Glossostigma cleistanthum)
Photo credit: Robert Whyte (at Bush Blitz Kiwirrkurra,
funded by the Australian Government and BHP Billiton)


(Glossostigma cleistanthum)

Report this Species!

If you believe you have found this species anywhere in Pennsylvania, please report your findings to iMapInvasives by submitting an observation record.

Species at a Glance

Mudmat is a low-growing, mat-forming, aquatic invasive plant that has remained largely under the radar due to its small size and the public’s lack of familiarity with it. The plant itself is usually less than 2 cm (0.8 in) high and can be found submerged in the water or emerging above the water’s surface.


Leaves: Bright green paired leaves resemble tiny rabbit ears. They are narrow, about 1- 4 cm (0.4-1.6 in) in length, and are slightly expanded at the tip. They taper to the base and may be sessile or stalked. Leaf margins are smooth.


Flowers: Small 1-3 mm (0.04-0.1 in) wide flowers are inconspicuous in the leaf axils at the base of the plant. They emerge when the water recedes in the summer months. Color ranges from mauve, lilac, pink, blue, and bluish-white to white. Closed, self- fertilizing flowers called cleistogams are also produced underwater in the soil among the roots.


Fruits: Round, thin-walled capsules are divided into two cavities that contain many small dark brown seeds.


Stems/Roots: Creep horizontally just below the soil surface and root along the nodes.

Similar Species

Native mudwort species (Limosella spp.) closely resemble mudmat. It may also be confused with emergent leaf forms of some members of the bladderworts (Utricularia spp.).


Mudmat prefers conditions with low pH, conductivity, and phosphorous in shallow waters, swamps, and periodically flooded areas with little wave action.


Initial introduction of mudmat probably occurred by aquarium release and its subsequent spread may have been mediated by both human activities, such as recreational boating, and by natural means, such as hitchhiking on migrating geese or other waterfowl.


Native to Australia, New Zealand, India, and east Africa, mudmat was discovered in the United States in 1992 at a single location in southern Connecticut. In the Mid-Atlantic, it can be found in areas of Pennsylvania, New Jersey, Delaware, and Maryland.


Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.

Environmental Impacts

Mudmat forms thick carpet-like mats that smother the lake bottom from the shoreline to depths of greater than 2 m  (6.6 ft). It spreads very rapidly, covering prime shoreline habitat, reducing biodiversity, and threatening native plant and animal communities.


Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).

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