The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Ludwigia hexapetala
Ludwigia hexapetala
(six petal water primrose)

Copyright Info
Ludwigia hexapetala (Hook. & Arn.) Zardini, H.Y. Gu & P.H. Raven

Common name: six petal water primrose

Synonyms and Other Names:  Ludwigia grandiflora ssp. hexapetala (Hook. & Arn.) G.L. Nesom & Kartesz

Taxonomy: available through www.itis.govITIS logo

Identification: According to Godfrey and Wooten (1981):

Habit: Perennial, floating and emergent, herbaceous forb

Stem/roots: non-flowering, sprawling stems float along the water surface with roots at the stem nodes; upright stems freely branching and flowering; pubescent

Leaves: alternating leaves on floating stems are spatulate (spoon-shaped), petiolate (leaf stems), and have rounded apices; alternating leaves on upright stems are lanceolate (lance-shaped), mostly sessile, and have acute apices; pubescent

Flowers: solitary flowers at leaf axils of upright stems; pedicels 1-5 cm, usually confused with floral tubes; a pair of small bractlets indicate the separation of the pedicel and floral tube; pedicel and floral tube pubescent; calyx of 5, sometimes 6, acute sepals, 10-12 mm, pubescent on the outside; corolla of 5, sometimes 6, bright yellow, rounded petals, 1-2 cm long and wide; stamens 8-12, twice the amount of sepals/petals

Fruits: fruit a pubescent, cylindric capsule 1-2.5 cm long, 3-4 mm wide

Look-alikes: Many Ludwigia species have similar leaves and flowers, but those two organs are key to determining identity. The alternate leave arrangement, the 8-12 stamens, and the 5-6 petals differentiate to about four species. The Ludwigia uruguayensis species complex includes L. grandiflora and L. hexapetala. Leaves on upright stems will be mostly lanceolate (widest portion of the leaf in the leaf center) on L. grandiflora and mostly oblanceolate (widest portion of the leaf in the top half of the leaf) on L. hexapetala, and stem nodes are swollen along the lower portion of upright stems on L. hexapetala (Colette Jacono, Univ. of Florida, pers. comm. 2017). Upright stems of L. hexapetala have pubescent stems, leaves, and floral tubes, distinguishing them from L. peploides, which are mostly glabrous (hairless) and lack upright stems. Floral tubes/capsules of L. hexapetala are narrower and longer than those of L. peruviana, which have stout and pyramidal floral tubes/capsules. The native L. leptocarpa has smaller petals (<1 cm) than those of L. hexapetala (>1 cm), usually the same length as the sepals.

Native Range: Ludwigia hexapetala is native to South America.

There is questions if the species is native to the southeastern US. Its earliest records date to South Carolina in 1844 and Georgia in 1864; its unclear if these records reflect a lack of early collections or introductions (Jacono 2014).


Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

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 Ludwigia hexapetala are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CA1902202023Butte Creek; Clear Creek-Sacramento River; Cottonwood-Tijuana; Coyote; Honcut Headwaters-Lower Feather; Honey-Eagle Lakes; Lower American; Lower Sacramento; Newport Bay; Russian; Sacramento-Stone Corral; Salinas; San Diego; San Joaquin Delta; San Luis Rey-Escondido; San Pablo Bay; Santa Clara; Santa Margarita; Tomales-Drake Bays; Upper Cache; Upper Cosumnes; Upper Putah; Ventura
GA201920202Lower Flint; Upper Oconee
LA201420162Boeuf; East Central Louisiana Coastal
MS200820081Upper Tombigbee
NC195720208Deep; Haw; Lower Cape Fear; New River; Upper Cape Fear; Upper Catawba; Upper Neuse; Upper Tar
OK194619461Lower Cimarron
OR200720194Lower Rogue; Middle Rogue; Middle Willamette; Upper Willamette
SC1981202016Black; Broad-St. Helena; Carolina Coastal-Sampit; Cooper; Enoree; Lake Marion; Lower Broad; Lower Catawba; Lower Savannah; Middle Savannah; Salkehatchie; Saluda; Santee; South Carolina Coastal; Tyger; Upper Broad
WA199420181Lower Columbia-Clatskanie

Table last updated 1/23/2022

† Populations may not be currently present.


Life history: Seeds germinate at 20°C after 6 weeks of cold stratification at 4°C; seedlings are rare; mostly reproduced by vegetative stem fragments; flowers from summer to November; seeds remain embedded in woody capsules (Okada et al. 2009; Les 2018)

Habitat: marshes, swamps, ponds, lakes, ditches, canals, and wet disturbed areas with high nitrogen and phosphorus (Godfrey and Wooten 1981; Les 2018)

Tolerances: full sunlight; depths to 1 m; elevations to 405 m; gravel, mud, sand, silt, and silty loam; tolerates dry and anaerobic conditions (Les 2018)

Community interactions: associated diatom communities shift towards shade-tolerant species under dense patches of L. hexapetala (Les 2018)

Means of Introduction: The primary introduction pathway is through the ornamental plant trade (Jacono 2014). Secondarily L. hexapetala is dispersed as stem fragments carried by water and waterfowl (Les 2018).

Impact of Introduction:
Summary of species impacts derived from literature review. Click on an icon to find out more...

EcologicalEconomicHuman HealthOther

Ecological impacts

Ludwigia hexapetala can grow as impenetrable mats at the water surface, blocking incoming sunlight, decreasing dissolved oxygen, and reducing available habitat for waterfowl, fish, and turtles (Alkhadher 2016; Grewell et al. 2016). It provides foraging habitat for the Giant Garter Snake, Thamnophis gigas, in Sacramento, California (Halstead et al. 2016). The species releases allelopathic chemicals, which impacts the growth rates and biomass of other plants, including Ceratophyllum demersum and Myriophyllum aquaticum (Thiébaut et al. 2019; Thouvenot et al. 2013).

Economic and human health impacts

Ludwigia hexapetala inhibits access to waterways for boating, fishing, hunting, and swimming, and it impedes important water conveyance systems including water supply canals and wetland preserves for urban and industrial water use and agricultural irrigation (Grewell et al. 2016). Dense mats of L. hexapelata inhibit the effective application of larvicides for mosquito control, which facilitates the spread of West Nile Virus (Meisler 2009).

References: (click for full references)

Alkhadher, M. 2016. South American aquatic weed is here to stay at Eugene’s Delta Ponds, but city succeeds in substantially knocking it back. The Register-Guard. Eugene, OR. http://registerguard.com/rg/news/local/34662990-75/story.csp. Created on 08/11/2016. Accessed on 08/11/2016.

Godfrey, R.K., and J.W. Wooten. 1981. Aquatic and Wetland Plants of the Southeastern United States, dicotyledons. University of Georgia, Athens, GA.

Grewell, B.J., M.D. Netherland, and M.J. Skaer Thomason. 2016. Establishing research and management priorities for invasive water primroses (Ludwigia spp.). U.S. Army Corps of Engineers, Engineer Research and Development Center, Vicksburg, MS. https://apps.dtic.mil/sti/pdfs/AD1002917.pdf.

Halstead, B.J., P. Valcarcel, G.D. Wylie, P.S. Coates, M.L. Casazza, and D.K. Rosenberg. 2016. Active season microhabitat and vegetation selection by giant gartersnakes associated with a restored marsh in California. Journal of Fish and Wildlife Management 7(2):397-407. https://doi.org/10.3996/042016-JFWM-029.

Jacono, C. 2014. A note on Florida's latest waterprimrose, Ludwigia hexapetala. Aquatics 36(1):15-16. https://plants-archive.ifas.ufl.edu/wp-content/uploads/files/caip/pdfs/LudwigiaHexapetala-fromAquaticsSpring2014.pdf.

Les, D.H. 2018. Aquatic dicotyledons of North America: ecology, life history, and systematics. CRC Press, Boca Raton, FL.

Meisler, J. 2009. Lessons from Ludwigia control in Sonoma County. Cal-IPC News. Berkeley, CA. 17 (2):4-5. https://www.cal-ipc.org/docs/resources/news/pdf/Cal-IPC_News_Summer09.pdf.

Okada, M., B. Grewell, M. Jasieniuk. 2009. Clonal spread of invasive Ludwigia hexapetala and L. grandiflora in freshwater wetlands of California. Aquatic Botany 91:123-129.

Thiébaut, G., L. Thouvenot, and H. Rodríguez-Pérez. 2018. Allelopathic effect of the invasive Ludwigia hexapetala on growth of three macrophyte species. Frontiers in Plant Science 9(1835):1-10. https://doi.org/10.3389/fpls.2018.01835.

Thiébaut, G., H. Rodriguez-Perez, and O. Jambon. 2019. Reciprocal interactions between the native Mentha aquatica and the invasive Ludwigia hexapetala in an outdoor experiment. Aquatic Botany 157:17-23. https://doi.org/10.1016/j.aquabot.2019.05.005.

Thouvenot, L., C. Puech, L. Martinez, J. Haury, G. Thiébaut. 2013. Strategies of the invasive macrophyte Ludwigia grandiflora in its introduced range: Competition, facilitation or coexistence with native and exotic species? Aquatic Botany 107:8-16. https://doi.org/10.1016/j.aquabot.2013.01.003.

Author: Pfingsten, I., Procopio, J., and Daniel, W.M.

Revision Date: 11/2/2021

Citation Information:
Pfingsten, I., Procopio, J., and Daniel, W.M., 2022, Ludwigia hexapetala (Hook. & Arn.) Zardini, H.Y. Gu & P.H. Raven: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=2979, Revision Date: 11/2/2021, Access Date: 1/23/2022

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.


The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2022]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [1/23/2022].

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