Myriophyllum pinnatum
(cutleaf watermilfoil)

Identity

Preferred Scientific Name

• Myriophyllum pinnatum (Walter) Britton, Sterns & Poggenb.

Preferred Common Name

• cutleaf watermilfoil

Other Scientific Names

• Myriophyllum scabratum Michx.
• Potamogeton pinnatum Walter

International Common Names

• English: foxtail green; green foxtail; green myrio
• Spanish: cola de zorra verde; milenrama; ramo-cola de zorra

Local Common Names

• Canada: cutleaf water-milfoil; green parrot’s feather
• Cuba: miriofilum; pinillo
• Hungary: grϋnes tausenblatt; stolístek zpeřeny; zierliches tausendblatt
• USA: alternate-leaved water-milfoil; Eastern water-milfoil; foxtail moss; pinnate water-milfoil; rooted coontail; rough water milfoil

Summary of Invasiveness

Myriophyllum pinnatum is a perennial aquatic herb only reported as invasive in Cuba, where it is included in the management plan of the Ciénaga de Zapata Biosphere Reserve as a species that needs to be managed to prevent invasion of that wetland system. In some areas of its native range in North America, it is considered rare, endangered or extirpated due to habitat fragmentation and loss. In the USA, the species is considered endangered in Connecticut, Massachusetts, Indiana, New Jersey, New York, Rhode Island and Tennessee. M. pinnatum belongs to a genus recognized for the invasive species M. spicatum, M. aquaticum and M. heterophyllum. 

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Haloragidales
•                         Family: Haloragidaceae
•                             Genus: Myriophyllum
•                                 Species: Myriophyllum pinnatum

Notes on Taxonomy and Nomenclature

Myriophyllum is one of the most species rich aquatic genera, with about 68 species spread worldwide (Moody and Les, 2010). The word Myriophyllum comes from the Greek, meaning many leaves and pinnatum means feather-like (SEINet, 2017). Species identification in this genus is difficult without the presence of reproductive structures.

Description

Perennial aquatic or semi-aquatic herb. Stem highly variable, rooting in mud and freely branching or elongating in deeper water. Leaves alternate and whorled on same plant, pinnately divided, with submersed leaves having three to five pairs of divisions. Emersed leaves are 0.5-3 cm long, linear to lance-shaped, and have comb-like divisions or sharp teeth. Flowers either male or female, found on the same plant (monoecious), some bisexual, borne in a terminal spike above the water surface, with male flowers near the inflorescence tip. Bracts are longer than male flowers, triangular, with six to ten 1-2 mm long teeth that are angled toward the tip. Flowers green to purplish, small, four-parted, with 1.5-2 mm long petals that are rounded above and narrow-clawed. Fruit is a deeply four-lobed nut-like cluster, pale, 1.3-2 mm long, egg-shaped to cubic, splitting into four one-seeded segments that are flat-sided with two spiked ridges. Winter buds absent (Red de Herbarios del Noroeste de México, 2017).

Distribution

M. pinnatum is native to North America, with evidence of its presence in Iowa since the Holocene (Baker et al., 1996; USDA-NRCS, 2017). Urquiola Cruz and Betancourt Gandul (2000) consider the species native to Cuba, but Maldonado González (2009-2010) and Oviedo Prieto et al. (2012) list it as introduced in the country. M. pinnatum has also been introduced to Mexico (in 1974) and to Jamaica (in 1976) (Proctor, 1982; Red de Herbarios del Noroeste de México, 2017). Although the species is not listed as naturalized elsewhere, it is sold commercially worldwide and on the internet to be used in freshwater aquaria.

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Risk of Introduction

M. pinnatum is an aquatic herb with a low to medium risk of introduction. Although it is available commercially at aquarium supply stores, its specific water temperature and pH might limit its distribution (Live Aquaria, 2017). Where used only as a plant for indoor aquaria, the threat to natural environments is low. It can become problematic if its popularity increases or if used in sewage treatment plants (Mohan et al., 2010; Live Aquaria, 2017).

Habitat

M. pinnatum occurs in shallow water, in ditches and ponds, usually less than 1 m deep (Knepper et al., 2002; SEINet, 2017). It is also reported from forest swales, wetlands, creeks, borders of brackish marshes, swamps and rivers (Fernald, 1936; Abbott and Judd, 2000; Rosen et al., 2003; Hercombe et al., 2007; Maldonado González, 2009-2010). 

Habitat List

Biology and Ecology

Genetics

The chromosome number reported for M. pinnatum is n = 5 (Moody and Les, 2002). DNA barcode information for the species is available at the Barcode of Life Data Systems (BOLD, 2017). Although hybridisation with M. heterophyllum was initially reported by Moody and Les (2002), the same authors later confirmed it to be between M. heterophyllum and M. laxum (Moody and Les, 2010).

Reproductive Biology

M. pinnatum reproduces by cuttings and by flowers, if tips are left to grow outside of water (Live Aquaria, 2017). Propagation procedures in vitro have been developed for the species by Kane and Gilman (1991).

Physiology and Phenology

M. pinnatum is a rapid growing aquatic herb that can grow partially above water (Live Aquaria, 2017). It is reported to flower in July (SEINet, 2017).

Associations

Sorrie (1987) reports the species to occur in small, shallow, muddy, brackish ponds, together with Typha latifolia, Phragmites communis [Phragmites australis], Eleocharis smallii [Eleocharis palustris], Scirpus validus [Schoenoplectus tabernaemontani], Hibiscus palustris [Hibiscus moscheutos], Ludwigia palustris, Proserpinaca palustris and occasionally Diplachne maritima [Leptochloa fusca subsp. fascicularis]. In some cases, P. australis can be a threat to M. pinnatum populations, by severely reducing the open water and exposed mud available.

Environmental Requirements

Most information available concerns cultivation of M. pinnatum as an aquarium plant. The species grows in shallow water in full to partial shade, at water temperatures of 16-24°C. It grows in clay, sand, limestone and gravel substrates, with water pH of 6.5-7.5 and water hardness of 3-8 mg/l CaCO₃ (Maldonado González, 2009-2010; Live Aquaria, 2017).

Although information about environmental requirements from natural habitats is lacking, the species is likely able to tolerate freezing temperatures, given the fact that it is native in Canada (Missouri Botanical Garden, 2017).

Climate

Latitude/Altitude Ranges

Air Temperature

Water Tolerances

Natural enemies

Notes on Natural Enemies

The species is foraged by Procambarus clarkii, P. spiculifer, Branta canadensis and Aix sponsa (Drobney and Fredrickson, 1979; Cronin et al., 2002; Parker et al., 2007).

Means of Movement and Dispersal

Intentional Introduction

M. pinnatum is widely used as an aquarium plant (Live Aquaria, 2017). Because of this, it is sold commercially at aquarium supply stores worldwide and on the internet, which facilitates its spread.

The species is also maintained as part of the permanent National Botanical Garden collection in Cuba (Maldonado González, 2009-2010).

Environmental Impact

In Cuba, M. pinnatum is considered a transformer species and listed as invasive (Oviedo Prieto et al., 2012). 

Social Impact

M. pinnatum has been associated with larvae of the malaria transmitting Anopheles mosquito (Penfound, 1942).

Risk and Impact Factors

• Proved invasive outside its native range
• Has a broad native range
• Fast growing
• Has high reproductive potential
• Gregarious
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Highly likely to be transported internationally deliberately

Uses

Economic Value

M. pinnatum is sold by aquarium shops and on internet websites. In some websites it is listed as being farm-raised for aquarium sales (Live Aquaria, 2017).

Social Benefit

M. pinnatum is reported as having some antimicrobial activity (Nickell, 1959). It is recommended for sewage treatment systems, as it improves dissolved oxygen levels in water, providing a good habitat for bacteria growth (Mohan et al., 2010).

Environmental Services

M. pinnatum provides coverage and protection to newborn fish and tadpoles (Morin, 1981; Live Aquaria, 2017). It is foraged by the crayfishes Procambarus clarkii and P. spiculifer, the Canada goose Branta canadensis and the wood duck Aix sponsa (Drobney and Fredrickson, 1979; Cronin et al., 2002; Parker et al., 2007). It is a host species for aquatic and semiaquatic Lepidoptera (Minno, 1992).

Similarities to Other Species/Conditions

M. pinnatum has both alternate and whorled leaves, while other Myriophyllum species have only whorled leaves (SEINet, 2017). The species is similar to M. farwellii, but the fruits are smaller in M. pinnatum. Also, the carpels of M. pinnatum are broadly two-winged on the back, strongly scabrate or toothed and deeply grooved between the wings, while in M. farwellii carpels are roughly tuberculate or slightly toothed and with shallow groves between them (Morong, 1891).

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Prevention

M. pinnatum is included in the Ciénaga de Zapata Biosphere Reserve management plan as a species that needs to be managed in order to prevent its spread in this wetland system (Oviedo Prieto et al., 2012).

Gaps in Knowledge/Research Needs

More detailed information about the species impacts on invaded habitats or on other species is needed. Details about its biology and environmental requirements in natural habitats are also needed.

References

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Links to Websites

Contributors

28/02/17 Original text by:

Jeanine Vélez-Gavilán, Department of Biology, University of Puerto Rico,  Mayaguez, Puerto Rico, USA 

Distribution Maps