Heteranthera reniformis Ruiz & Pav., Pontederiaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Plant Pest Risk Assessment for Heteranthera reniformis from the Department of Primary Industry, Queensland, Australia (PDF format)

Common name(s): [more details]

English: kidneyleaf mudplantain

Habit:  aquatic herb

Description:  "Plants annual or facultatively perennial. Vegetative stems submersed with elongate internodes, or emersed and procumbent. Flowering stems 1-9 cm, distal internode 0.5-4 cm. Sessile leaves forming basal rosette, blade linear to oblanceolate, thin, 2.4-3.7 cm x 3-8 mm. Petiolate leaves floating or emersed; stipule 1-5 cm; petiole 2-13 cm; blade reniform, 1-4 x 1-5 cm, length equal to or less than width, apex obtuse. Inflorescences spicate, 2-8-flowered, elongating in 1 day, usually shorter than spathes, terminal flower sometimes extending beyond spathe apex; spathes 0.8-5.5 cm, glabrous; peduncle 0.5-4.2 cm, glabrous. Flowers opening ca. 3 hours after sunrise, wilting by early afternoon; perianth white, salverform, tube 5-10 mm, limbs zygomorphic, lobes narrowly elliptic, 3-6.5 mm, distal central lobe with yellow or green region at base, sometimes with distal brown spot; stamens unequal, lateral stamens 0.9-2.2 mm, filaments linear, pubescent with white multicellular hairs toward apex; central stamen 2.2-4.7 mm, filament sparsely pubescent with multicellular hairs; style pubescent with multicellular hairs. Seeds 8-14-winged, 0.5-0.9 x 0.3-0.5 mm"  (Flora of North America online).

Habitat/ecology:  "Roadside ditches, edges of streams and ponds, freshwater tidal mudflats; 0-2600 m"  (Flora of North America online).  "H. reniformis is adapted to open, sunny sites with nutrient-rich soil and shallow water (less than 15 cm deep). Because it is a poor competitor with many sedges, rushes and other wetland species, H. reniformis is easily crowded out of wetlands. It is, however, able to take advantage of favourable situations quickly, such as recently inundated areas (e.g. following flooding, beaver dams or human activity) and areas where competition has been destroyed or otherwise removed (as in the case of herbicide use). As a result, this species is found in seemingly disjunct and dissimilar areas such as ponds and sinkholes, rice fields, ditches, and powerline corridors." (Queensland DPI risk assessment)

Propagation:  "Since the stems of H. reniformis produce roots at each node, it is expected that any broken fragments of stems, with one or more nodes intact, could be washed downstream to infest new areas. A single flood-event is likely to disperse stem fragments over a considerable distance.  Each fruit on H. reniformis contains 8-14 winged seeds. While this study was unable to find published information on dispersal, it is reasonable to assume that these winged seeds can be dispersed by wind and water.  Seed banks may exist in the soil for many years. Optimum conditions for seed germination may include daily fluctuations in temperature. These fluctuations naturally raise and lower soluble oxygen levels and may act as a trigger for germination."(Queensland DPI risk assessment)

Native range:  Eastern United States, Mexico, throughout Central America, scattered in South America  (Flora of North America online).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Frohlich, Danielle/Lau, Alex (2014) (p. 14) "This species, with documented negative impacts to agricultural yields in rice fields (Ferrero 1996), has now been documented on O'ahu from a lo'i kalo in Waihe'e. Local farmers estimated significant reductions in yield at the site, where it was found in multiple kalo (Colocasia esculenta) patches on two farms in the area. control of the species has been difficult, and one current strategy has been to dry, then flood, individual patches to induce germination out of the seed bank, then removing the plants before they set new seed. This species has been rated as high risk by the Hawai'i-Pacific Weed risk assessment (anonymous 2013), and should be monitored for and controlled throughout the state, where possible. one potential vector for long term dispersal of this species could be seeds or other propagules hitchhiking on shared huli between farms within andbetween islands."

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Queensland	introduced invasive	Csurhes, Steve (2008) (p. 2)
Central America Central America (Pacific rim)	El Salvador (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Guatemala (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Nicaragua (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Panama (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013) Chiapas, Hidalgo, Jalisco, Michoacan
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	United States (other states)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (continental except west coast) United States (other states)	USA (Florida)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Control: 

Chemical:  "Experiments to control common Heteranthera species within flooded rice in Italy found that cinosulfuron (sulfonylurea) showed the highest effectiveness and selectivity, even when applied in very low amounts."(Queensland DPI risk assessment)