• herbaceous perennial
• amphibious, "obligate" (requiring a wet habitat)
• in freshwaters, mostly submersed, partly emersed
• growing from bottom to surface in water to 10 feet deep, or found creeping along edges
• forming dense stands of stems in the water, later in the season breaking loose to form large floating mats
• rarely, terrestrial growth form grows in moist soil (McCann)
• flowering in fall and winter
• reproduces asexually (regrows from plant fragments) and perhaps sexually (from seed), however Sutton (1996) says it's unknown whether seeds play a major part in its spread
• stems fragment easily and are able to develop new plants from small fragments; reportedly even a free-floating leaf can form a new plant

Habitat:

• in warmer climates; preferring flowing streams, but also may be found in slow-moving waters and in lakes
• temperature tolerance: minimum temperature, 4^o C (39^o F); optimum temperature, 22-28^o C (71-82^o F); maximum temperature, 30^o C (86^o F) (Kasselmann 1995)
• best light intensity for hygrophila growth is around 110 micro-einsteins/meter squared/hour (Cobb and Haller, 1981) (what is light intensity of site under trees in warm weather?)
• low light compensation and saturation points and low CO₂ compensation point make it a competitive plant because it can start growing in low light before other plants do (Spencer & Bowes 1985, Bots et al. 1990 - from Angerstein 1994)
• tolerates a range of pH and water hardness conditions

Quick ID:

Hygrophila polysperma: medium-small sized, floating or emersed plants; emersed stems may be squarish, submersed stems are round; leaves opposite with no stalks or (on underwater leaves) short stalks; small bluish-white flowers with no stalks, attached in upper leaf axils

More complete identification:

Hygrophila polysperma (Roxb.) T. Anderson

Original description: J. Linn. Soc., Bot. 9:426. 1876.



• dicot
• rooted in the hydro-soil
• stems creeping ascendant (rarely erect); to 6 feet and longer; upper most emersed stems may be squarish; stems are brittle and easily break into fragments
• leaves opposite (on the stem); simple; sparsely hairy; with pointed tips (acute)
• leaf color variable, light green to brown to reddish
• leaves submersed and emersed are more or less the same shape; mostly 1.5 in. long, .5 in. wide, but can be larger
  • emersed leaves elliptic to obovate-elliptic; having no leaf stalks (sessile)
    
  • submersed leaves larger and thinner than emersed leaves, broadly elliptic, broader toward tip; having short stalks
• flowering in fall and winter (in Florida), October to early March (Sutton 1996)
• flowers small, to 3/8 in. long, solitary, without stalks; found in leaf axils (angle where leaf meets the stem) in the apical (uppermost) parts of the emersed stems; corolla (petals) bluish-white to white, hairy, with two "lips", upper lip 2-lobed, lower lip 3-lobed; calyx (leaves covering the bottom part of the flower) hairy with 5 equal lobes
• rooting at stem nodes; many roots
• fruit a narrow capsule 6-7 mm long; 20-30 tiny flattened-round seeds

• non-native alligator weed (Alternanthera philoxeroides):
  
  --alligator weed has largish white papery flowers which are totally different
  

• native red ludwigia (Ludwigia repens):
  
  -- red ludwigia has yellow flowers with 4 petals (however the petals fall off quickly, so they are rarely seen); purple pigment throughout, especially in submersed leaves; blunt leaf tips
  

• native lake hygrophila (Hygrophila costata (H. lacustris)):
  
  -- lake hygrophila is entirely emersed or terrestrial; much larger and taller (to 80 cm); mostly erect; much larger leaves; flowers along the entire stem (rather than just at the top)
  

• Hygrophila polysperma is naturalized in many regions of Florida and in south central Texas

  U.S. Drainage Distribution Map of Hygrophila polysperma was prepared by C. Jacono of the U.S. Geological Survey, Nonindigenous Aquatic Species Program, which is located on the USGS-NAS web site.
  

  The best way to track the spread of invasive aquatic plants may be to identify the drainage basins (watersheds) they have been discovered in. Drainage maps give useful information to eco-managers because drainage maps show precisely where the plants are, making it easier for managers to infer where the plants might go next, and thus where to take preventive measures.
  

• Hygrophila polysperma was brought to the U.S. as an aquarium plant about 1945 as "oriental ludwigia" (Innes 1947);
• was cultivated in Ohio at the end of WWII by aquarium dealer (Reams 1953);
• was first found in Florida near Tampa in 1965, but not correctly identified till 1977 (Les and Wunderlin 1981);
• was first reported as a weed problem in south Florida canals in 1980;
• and had spread to 18 Florida public water bodies by 1994.

  Hygrophila polysperma continues to be sold through aquarium supply dealers and over the Internet, even though the plant is on the U.S. Federal Noxious Weed List.
  

Hygrophila polysperma is difficult to control:

the action of mechanical harvestors and chopping machines fragment the hygrophila plants and increase their distribution;


the herbivorous (plant-eating) biological control fish, the Chinese grass carp, have a low preference for hygrophila (Cassani); triploid grass carp reportedly were "used successfully in canals to control hygrophila" (Ferriter et al. in Simberloff 1997, p. 319); no other biological control work has been done for this species (Pemberton, 1996)


registered aquatic herbicides provide only marginal control of hygrophila; hygrophila is relatively resistant to herbicides that control hydrilla (Vanadiver 1980; Sutton 1996); hygrophila is much more difficult to control with herbicides than is hydrilla, and requires higher rates of herbicides (Hall and Vandiver, 1990); treatments using copper plus Reward herbicides combined showed little effect on this plant in Florida canals 4 weeks after application (Sutton 1996)


From the University of Florida Aquatic Weed Management Guide, Vandiver 1999:


According to this Guide, the only herbicide labelled to be used against hygrophila is "Aquathol Super K Granular Aquatic Herbicide", having the active ingredient, "endothall". This herbicide is labelled to be legally used in Florida canals, drainage ditches, lakes, ponds, reservoirs, rivers and streams. It is unknown at this time to this author whether this herbicide may legally be used against hygrophila in other states. As always, comply with federal law by following the herbicide label instructions, permissible sites and application rates.

There's plenty you can do to help.

The information contained on this wep page was extracted from published scientific literature and agency reports. It is important to know that plant research, like most areas of scientific research, is still relatively young and incomplete--much may have been published about the physiology of one plant but not about its management; much may have been published about how to culture and grow another plant but not about its natural ecology. Thousands of research articles may have been published about one invasive plant, but perhaps only a dozen about another.

If you want to read the research yourself, perhaps to clarify or expand an area of information contained here, or to help determine your own line of research, you are welcome to query the world's largest collection of international scientific literature about aquatic, wetland and invasive plants, the APIRS bibliographic database, which contains more than 54,000 citations and their content keywords. Or you might want to ask us to do it for you and mail or e-mail the search results to you.

This is the literature about Hygrophila polysperma that was used to develop this web page. More research items about this plant may be found at APIRS:

• Angerstein MB, Lemke DE. 1994. First records of the aquatic weed Hygrophila polysperma (Acanthaceae) from Texas. Sida 16:365-71
• Bowes G. 1982. Baseline physiology of the potential problem plants, Limnophilia sessiliflora and Hygrophila polysperma. Dept. of Bot., Univ. of Florida, Gainesville, 17 pp.
• Cassani JR. 1996. Managing aquatic vegetation with grass garp. A guide for water resource managers. American Fisheries Soc., Introduced Fish Sect., Bethesda, MD., 196 pp.
• Cobb JE, Haller W. 1981. Annual Report, Florida Cooperative Agreement, Integrated Management of Aquatic Weeds 1980-1981. USDA/SEA/AR- University of Florida
• Hall DW, Vandiver VV Jr. 1990. Weeds in Florida. Gainesville: University of Florida, Institute of Food and Agricultural Sciences (IFAS). Publication SP 37. 43 pp.
• Innes WT. 1947. Hygrophila, a new aquarium plant. The Aquarium 16:30-1
• Kasselmann C. 1995. Aquarienpflanzen. Egen Ulmer GMBH & Co., Stuttgart. 472 pp. (In German)
• Les DH, Wunderlin RP. 1981. Hygrophila polysperma (Acanthacae). Florida Scientist 44:189-92
• McCann JA et al. 1996. Nonindigenous aquatic and selected terrestrial species of Florida-Status, pathway, and time of introduction, present distribution, and significant ecological and economic effects. Southeastern Biological Science Center, Gainesville, 256 pp.
• Miller JW. 1990. Florida aquaculture regulatory source book: leasing, licensing, and permitting requirements for aquaculture in Florida. FL Dept. Agric. Consumer Serv., Tallahassee, 238 pp.
• Pemberton RW. 1996. The potential of biological control for suppression of invasive weeds of southern environments. Castanea 61(3):313-319
• Reams WM. 1953. The occurrence and ontogeny of hydrothodes in Hygrophila polysperma T. Anders New Phyto. 52:8-13
• Schardt JD. 1997. Florida Aquatic Plant Survey 1994. Tech. report. Tallahassee: Florida. Dept of Environmental Protection. Report nr 972-CGA. 86 pp.
• Schardt JD, Schmitz DC. 1991. Florida Aquatic Plant Survey 1990. Tech. report. Tallahassee: Florida Dept. of Natural Resources. Report nr 91-CGA. 89 pp.
• Schmitz DC. 1985. Hygrophila polysperma, A review of the scientific literature. Tech. report. Tallahassee: Fla. Dept. of Natural Resources. 15 pp.
• Simberloff et al. 1997. Strangers in paradise- impact and management of non-indigenous species in Florida. Island Press, Washington, DC, 467 pp.
• Spencer W, Bowes G. 1984. Limnophilia and hygrophila: a review and physiological assessment of their weed potential in Florida. J. Aquat. Plant Manage. 23:7-16
• Stocker RK. 1996. Control technologies for use against the submersed aquatic weeds hydrilla and hygrophila. Semi-Annual Rept., USDA/ARS-IFAS, Gainesville, FL, 68 pp.
• Sutton DL. 1995. Hygrophila is replacing hydrilla in south Florida. Aquatics 17:4-10
• Van TK, Steward KK. 1982. Evaluation of chemicals for aquatic plant control. Annual Report 1981, Ft. Lauderdale, FL, 66 pp.
• Van dijk GM, Thayer DD, Haller WT. 1986. Growth of hygrophila in flowing water. J. Aquat. Plant Manage. 24:85-7
• Vandiver VV. 1999. Florida aquatic weed management guide. Univ. of FL, IFAS, Cooperative Extension Service, Publ. SP-55, 130 pp.
• Vandiver VV. 1980. Hygrophila. Aquatics 2:4-11
• Westbrooks RG, Eplee RE. 1996. Regulatory exclusions of harmful non-indigenous plants from the United States by USDA APHIS PPQ. Castanea 61:305-312
• Wunderlin RP, Hansen BF, Bridges EL. 1995 (updated May 1996). Atlas of Florida vascular plants. Website: http://www.usf.edu/~isb/projects/atlas/atlas.html
  

University of Florida Cooperative Extension Service Fact Sheets

http://edis.ifas.ufl.edu/BODY_FW019


USGS Nonindigenous Aquatic Species Fact Sheets

http://nas.er.usgs.gov/plants/docs/hy_polys.html