Common names: Water spangles, common salvinia, common watermoss

Family: Salviniaceae

Life form:  Aquatic fern

History & Introduction

Given its rapid growth and attractive floating leaves, water spangles has been a popular aquatic plant in aquariums, gardens, and greenhouses since its introduction to the United States in the 1880’s, with the first records of the plant in New York being made in 1898, on Staten Island. Although present in cultivation for decades, it only escaped into the wild in the 1920’s and 1930’s, when it entered local waterways in Florida through ponds and pools being flooded on private property. Since then, this invasive species has spread broadly across Southern states, parts of California, and has increasingly encroached into more temperate regions of the Northeast and Midwest. It is native to South America and parts of Central America

Identification & Biology

Water spangles are most commonly found in bodies of stagnant to slow-moving water. Much like other species of fern, water spangles do not produce flowers or seeds. But unlike some other fern species, water spangles do not reproduce via spores either. Although individuals of this species may produce spore-producing bodies known as sporocarps underneath their leaves/fronds—that would typically aid in sexual reproduction—it is largely believed that this species is actually sterile and instead relies on asexual means to clone and spread itself. Its system of underwater stems, or rhizomes, are the primary structure used to produce new individuals, which will eventually fragment off of the original plant.

Form: As suggested by its scientific and common name, water spangles is a small, free-floating aquatic plant. Younger plants with more space typically lay flat, while leaves/fronds on more mature plants fold upward at their midrib, appearing almost vertical. Colonies form dense mats over the water’s surface.                                           

Leaves/Fronds: Young plants initially exhibit only a single leaf that later becomes a whorl of three leaves at maturity. Two of these leaves remain at the surface of the water, while the third is submerged, highly divided, and acts as a sort of root system for the plant, as it is covered in rust-brown hair-like structures. Surface leaves vary in color from yellow-green to red-brown depending on age, and can be 0.4-2.0 cm long. Additionally, surface leaves have smooth margins, are oval in shape, and are slightly indented at their midrib. They are noticeably pubescent or hairy on their upper surface, exhibiting clumped white hairs that diverge at the top. These hairs are used to cling on to passing boats or animals, and to trap air on the surface of the leaves, giving the plant buoyancy. The darker underside of the leaf is also hairy, however these hairs are rust-brown and do not come in clumps.

Rhizomes: Mature plants often contain an underwater stem, or rhizome, extending horizontally. These act as runners which rise to the surface and sprout new leaves. Like stems, they have buds, but new growth may be limited in unideal conditions (drought, cold, etc.)

Sporocarps: These are small, football-shaped capsules that resemble a spiral of grapes growing on the underside of the plant. Sporocarps tend to come in groups of 4-8.

Damage & Concern

Water spangles pose a serious threat to plant and animal diversity in aquatic systems. Like many other invasive species, water spangles are able to outcompete native species, including duckweed, that serve as vital resources for wildlife. In areas where they are able to form thick mats over the water’s surface—such as in water that is slow-moving or stagnant—they can additionally block out sunlight to the water below. This is extremely detrimental to any submerged plants, and can cause mass die-offs, leading to a cascade of negative effects in the water column. 

Dissolved oxygen: Water bodies with substantial flow are able to transfer oxygen from the surface into the water column. This transfer is vital for contributing to the total dissolved oxygen that fish and invertebrates need to survive. However, in low-current or stagnant environments where water spangles thrive, it is unlikely that there is much surface transfer of oxygen occurring. This forces the wildlife in these environments to depend on photosynthesis by submerged plants as their primary source of dissolved oxygen. Consequently, it is imperative that invasions by water spangles, or similar floating invasives, be prevented or managed quickly to protect these plant and animal die-offs from occurring.

 

Societal Impacts: There is additional research that suggests that water spangles can negatively impact recreation and the economy. As water spangles reduce the presence of fish and other invertebrates, they provide an ideal habitat for the larvae of certain mosquito species to develop, thus increasing the local population and potential vectors of disease. Boating and drainage operations may also be inhibited as engines and pipes get tangled or clogged in dense mats of the plant, and in the agricultural realm, water spangles are a severe detriment to rice and crayfish farms, proving not only difficult towards crop production but expensive in terms of management as well.

Management

The best way to manage invasive species is to prevent their spread entirely. It is important to clean, drain, dry, and inspect all boating or fishing equipment prior to leaving one site, as this will limit hitchhiking. If spotted in small to medium quantities, manual removal of water spangles may still be possible, and involves some form of surface raking to remove the majority of plant matter. Again, being thorough is ideal, as even small fragments can fragment and create further colonies. Be prepared to make multiple site visits to ensure that all individuals of water spangle have been removed.

 

Larger infestations typically require herbicides or biocontrol to be effectively managed. Herbicides containing copper carbonate, diquat, glyphosate, flumioxazin or carfentrazone-ethyl have proved ideal  in short or long term management, depending on one’s resources and management plans. As always, be sure to consult your state’s herbicide regulations and your herbicide label before proceeding with chemical treatment for safe and effective control.

 

There have been a few different biocontrols employed globally to deal with water spangles. The salvinia weevil (Cyrtobagous salviniae), salvinia stem-borer moth (Samea multiplicalis), and waterfern weevil (Stenopelmus rufinasus) have all been used to limit or eradicate populations of water spangles with varying degrees of success. The most widely used biocontrol is the salvinia weevil, and it is native to Southeast Brazil. The salvinia stem-borer moth has also been shown to be somewhat effective at inhibiting rapid spreads of water spangles, and is native to Southern parts of the United States to Argentina. And lastly, the waterfern weevil has also been noted to feed on water spangles, but will only do so if none of its preferred plants are available, so success may be limited if water spangles is not dominant in your area. Please check local regulations to see if any of these options are available to you.

Monitoring or Reporting

As a Tier 2 in LIISMA’s Early Detection and Rapid Response program, we urge you to please report any sightings of water spangles to iMapInvasives or iNaturalist. Your observations are key to our mission, as they allow us to respond to emerging populations before becoming a larger threat to New York. To gain a better understanding of how we assign tiers to species, see this article.

 

iMapInvasives is a network for invasive species reporting, allowing concerned parties like LIISMA to discern where invasive species may be popping up, or their geographic extent. Similarly, iNaturalist functions as a biodiversity reporting platform for all kinds of living things—native or non-native—and can help anyone identify and share what species are inhabiting a given area. 

 

If you are interested in playing a bigger part in protecting our local flora and fauna, consider joining LIISMA’s Invasive Species Spotter Program! This program teaches you how to spot emerging invasive species as they arise, giving you valuable detection skills against occurrences of invasive species that were not previously on LIISMA’s radar.

References

Center for Aquatic and Invasive Species (2025). Salvinia minima. University of Florida. https://plant-directory.ifas.ufl.edu/plant-directory/salvinia-minima/

FLIP: Florida Invasive Plants (2025). Salvinia minima.https://plantatlas.usf.edu/flip/plant.aspx?id=38

Go Botany (2025). Salvinia minima – common watermoss. The Native Plant Trust. https://gobotany.nativeplanttrust.org/species/salvinia/minima/

Mikulyuk, A. and Nault, M. (2008). Salvinia minima. CABI Compendium. https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.107785

Morgan, H., Anemaet, E., and Lower, E. (2025). Salvinia minima. U.S. Geological Survey, Nonindigenous Aquatic Species Database. https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=297

Pham, K., Diaz, R., and Nachtrieb, J.G. (2022). Salvinias (Salvinia spp.): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association (NAISMA). https://bugwoodcloud.org/resource/files/26406.pdf

Steere Herbarium, Howe, M.A. (2025 & 1898). Salvinia minima, Baker. New York Botanical Garden. http://sweetgum.nybg.org/science/vh/specimen-details/?irn=4093697

Texas Invasive Species Institute (2014). Water Spangles. The Texas State University System. https://tsusinvasives.org/home/database/salvinia-minima

United States Environmental Protection Agency (2024). Dissolved Oxygen. https://www.epa.gov/caddis/dissolved-oxygen

U.S. Fish & Wildlife Services (2019). Water Spangles: Salvinia minima, Ecological Risk Screening Summary. https://www.fws.gov/sites/default/files/documents/Ecological-Risk-Screening-Summary-Water-Spangles.pdf