Elodea nuttallii
(Nuttall's waterweed)

Preferred Common Name

• Nuttall's waterweed

Other Scientific Names

• Anacharis nuttallii Planch., 1848
• Anacharis occidentalis (Pursh) Victorin
• Elodea columbiana H. St. John
• Elodea minor (Engelm. ex Caspary) Farw.
• Elodea occidentalis (Pursh) H. St. John
• Philotria angustifolia (Muhl.) Britton ex Rydb.
• Philotria minor (Engelm. ex Caspary) Small
• Philotria nuttallii (Planch.) Rydb., 1908
• Philotria occidentalis (Pursh) House
• Udora verticillata var. minor (L. f.) Spreng. Engelm. ex Caspary

International Common Names

• English: free-flowered waterweed; Nuttall waterweed; Nuttall's pondweed; slender waterweed; waterweed esthwaite; waterweed western; western elodea; western waterweed
• French: élodée a feuilles étroites; élodée de Nuttall

Local Common Names

• Denmark: smalbladet vandpest
• Germany: Nuttalls Wasserpest; Nuttall-wasserpest; Schmalblaettrige Wasserpest; Schmalblattrige Wasserpest; St. John- Wasserpest
• Italy: elodea di Nuttall; peste d'acqua di Nuttall
• Japan: Kokanadamo
• Netherlands: smalle waterpest
• Slovakia: vodomor Nuttalov
• Sweden: small vattenpest

EPPO code

• ELDNU (Elodea nuttallii)

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Hydrocharitales
•                         Family: Hydrocharitaceae
•                             Genus: Elodea
•                                 Species: Elodea nuttallii

Historically there has been much confusion in the classification of the species of the genus Elodea (Family Hydrocharitaceae). However, Cook and Urmi-König (1985), in the latest revision of the genus, recognize five species of Elodea, all of them from the New World: E. potamogeton (Bert) Espinosa, and E. callitrichoides (Rich.) Caspary are endemic to South America, while E.bifoliata St. John, E. canadensis and E. nuttallii grow in North America. Elodea nuttallii (Planch.) H. St. John, which is accepted by Tutin et al. (1980), was first named as Anacharis nuttallii Planchon in 1848 and later was replaced in the genus Elodea by St John in 1920. The taxon can be cited as H St. John or St John (IPNI, 2009). The epithet nuttallii, is after Thomas Nuttall (1786-1859), one of the first naturalists to explore the American West in the early nineteenth century.

E. nuttalli is a submerged-root aquatic plant, dioecious with floating flowers and rooting at nodes. The stems long and slender, often freely branched. Leaves pale green more or less equally spaced along the stem middle and upper leaves typically in whorls of 3 or occasionally 4, linear to narrowly lanceolate often recurved with folded margins; 6-13 mm long, 0.7-1.5 mm wide, acute at tip. Lower leaves in pairs and reduced in size, ovate-lanceolate. Stem slender, round in cross section, often freely branched, 30-100 cm long. Root white, unbranched, from nodes along the stem and not always present. The flower is small no more than 8 mm across; waxy white flowers occur at the ends of long, thread-like stalks and have 3 petals and usually 3 sepals. Male and female flowers occur on separate plants, but male flowers are rarely produced. Male flower spathes borne in middle axils, sessile, ovoid, about 2 mm long, spathe in 2 parts but the lobes twisted together so appears pointed; male flowers solitary and sessile in the spathe, breaking free and floating to the surface, where the flower opens, allowing pollen to drift on water's surface - hence the common name of free-flowering waterweed. Sepals ovate, about 2 mm long, sometimes reddish; petals lacking or to 0.5 mm long, ovate-lanceolate; stamens 9, pedicels briefly remaining attached following anthesis; inner 3 filaments connate proximally, forming column; anthers 1-1.4 mm; pollen in tetrads. Female flower spathes borne in upper axils, narrowly cylindric but slightly broadened at the base and the tip, 9-25 mm long; extended to the surface by a threadlike hypanthium up to 9 cm long; sepals green, tiny obovate, ca. 1 mm long; petals white, obovate, longer than the sepals; stigmas slender, slightly exceeding the sepals. Fruit narrowly ovoid to fusiform capsule, 5-7 mm long; containing several seeds. Ripens underwater. Seeds fusiform, 3.5-4.6 mm long, base with long hairs (Larson, 1993; FNA, 2009).

E. nuttallii was reported in Belgium in 1939 (with a definite identification in 1955) (Simpson, 1984); and in Britain in 1966, and spreading rapidly from 1970 onwards from the southeast and scattering throughout Wales, Scotland (Preston and Croft, 1997) and Ireland (1984). It was also reported in the Netherlands in 1941 and in Germany in 1961, where it has since spread across the country. There are also reports of finds in Denmark (1974) (DAISIE, 2009), in Switzerland, where it was reported in the 1980s, and is spreading along the Rodan (Rhone) river (CPS-SKEW, 2008). It was first found in Sweden in 1991, in Lake Mälaren (Anderberg, 1992) and, together with E. canadensis and Nymphoides peltata, it is one of the three most troublesome species in Sweden (Josefsson and Andersson, 2001). Thereafter, its spread was noted in 1998 in the Danube delta in Romania, covering the majority of the delta (Sârbu et al., 2006); and from there to Slovakia in 2001 (Otahelová and Valachovic, 2002) and Hungary (Mesterházy et al., 2009) and then spreading into Western Europe (Wittenberg, 2005; Branquart, 2007). It is not unlikely that additional finds have been made, but that they have been mistaken for Canadian waterweed. In Asia, it was reported for the first time in 1960 in Japan (Lake Biwa) (Ikushima and Caballa, 1965). Since then, it has expanded very rapidly, and is regarded as one of the most troublesome aquatic weeds together with Egeria densa (Kunii and Maeda, 1982; Oki, 1994; Nagasaka et al., 2002). It was also introduced into China around the 1980s (Xu et al., 2007).

Soil reaction

• alkaline
• neutral

Natural Dispersal (Non-Biotic)

E. nuttallii as well as E. canadensis have the potential to develop into dense submerged beds, which prevent the use of water for recreational and professional purposes (Larson, 2003), navigation and port infrastructure (CPS-SKEW, 2008). The plant can also clog and impede drainage waterways.

Impact on Habitats

E. nuttallii populations are rarely troublesome in natural habitats in North America, but plants can become dominant in altered or created aquatic systems, especially when bicarbonate, reduced iron, and phosphorus are plentiful (Thiébaut and De Nino, 2009). E. nuttallii tends to dominate native macrophyte communities, which may lead to their local extinction. This species may also have a significant impact on protected sites.

Impact on Biodiversity

It often forms dense, monospecific stands and displaces other aquatic plants from many localities (Simpson, 1984, 1990; Barrat-Segretain, 2005). E. nuttallii and E. canadensis have shading effects during phases of rapid growth and mass occurrence. The plants compete with and displace indigenous vegetation, thus reducing biodiversity (Josefsson and Andersson, 2001).

It is a submerged plant, and just like E. canadensis it forms large and dense stands that interfere with boating, fishing and adversely affect recreation activities.

• Proved invasive outside its native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Tolerant of shade
• Highly mobile locally
• Long lived
• Fast growing
• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Reproduces asexually
• Has high genetic variability

• Altered trophic level
• Changed gene pool/ selective loss of genotypes
• Conflict
• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Host damage
• Increases vulnerability to invasions
• Infrastructure damage
• Modification of hydrology
• Modification of natural benthic communities
• Modification of nutrient regime
• Modification of successional patterns
• Negatively impacts aquaculture/fisheries
• Negatively impacts tourism
• Reduced amenity values
• Reduced native biodiversity
• Soil accretion
• Threat to/ loss of native species

• Allelopathic
• Antagonistic (micro-organisms)
• Competition - monopolizing resources
• Competition - shading
• Filtration
• Interaction with other invasive species
• Rapid growth
• Rooting

• Highly likely to be transported internationally deliberately
• Highly likely to be transported internationally illegally
• Difficult to identify/detect as a commodity contaminant
• Difficult to identify/detect in the field
• Difficult/costly to control

Economic Value