|European and Mediterranean Plant Protection Organization
Organisation Européenne et Méditerranéenne pour la Protection des Plantes
EPPO Data sheets on invasive alien plants
Fiches informatives sur les plantes exotiques envahissantes
Pontederia cordata L.
Pontederiaceae – Pickerelweed
Scientific name: Pontederia cordata L.
Synonyms: Narukila cordata (L.) Nieuwl., Narukila cordata var. lancifolia, Pontederia angustifolia Pursh, Pontederia lanceolate Nutt., Pontederia lancifolia Muhl., Pontederia maculate Donn., Pontederia mucronata Raf. Ex Torr., Pontederia nymphaeifolia Kunth, Pontederia obtusifolia (Raf.) A.DC., Pontederia ovalis Mart. Ex Schult. & Schult. F., Sagittaria cerulea Raf., Umsema mucronata Raf., Umsema obtusifolia Raf., Unisema cordata (L.) Farw., Unisema deltifolia Raf., Unisema heterophylla Raf., Unisema lancifolia Raf., Unisema latifolia Raf., Unisema media Raf., Unisema mucronata Raf., Unisema obliquata Raf., Unisema obtusifolia (Raf.) Raf., Unisema peduncularis Raf., Unisema purshiana Raf., Unisema rotundifolia Raf. (the plant list website).
Basionym: Pontederia cordata L. Sp. Pl. 1: 288 
Taxonomic position: Magnoliophyta, Liliopsida, Commelinales, Pontederiaceae
Common names: Pickerelweed (English), Moerashyacint (Dutch), Pontederia (Italian), Pontédérie à feuilles cordées (French)
EPPO code: POFCO
There is no regulatory status for this species.
EPPO region: Belgium, France, Italy, Ireland, Netherlands, Spain, Switzerland, United Kingdom.
Africa: Kenya, South Africa, Tanzania and Uganda
North America: (native): Canada (New Brunswick, Nova Scotia, Maine, Quebec), USA (Alabama, Arkansas, Connecticut, Florida, Georgia, Illinois, Kansas, Kentucky, Louisiana, Massachusetts, Mississippi, Michigan, Missouri, Nebraska, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Ontario, Oregon, Pennsylvania, Rhode Island, South Carolina, Texas, Vermont, Virginia, West Virginia)
South America: Argentina
Oceanic: Australia (widespread but scattered populations in New South Wales, Victoria and South-West Australia)
History of introduction and spread
In North America, native range of P. cordata extends from Nova Scotia (Canada) to South Florida and Texas (USA). The species is also recorded as being native in Argentina (Zuloaga & Morrone 1996). In the United Kingdom, P. cordata occurs in the south of England and extends up to the city of Manchester. The first record of P. cordata was from Dorset (UK) in 1949. The plant is also recorded in the South West of Ireland. In Belgium, P. cordata was first found in a pond near Huldenberg in 1985 (Meert 1988) cited in: National Botanic garden of Belgium (2015). Further observations were recorded in 2010 in Ottignies (Bois de Lauzelle). The species is recorded to form large stands in natural and vulnerable habitats in Belgium (National Botanic Garden of Belgium, 2015). In Victoria, Australia, P. cordata is regarded as an environmental weed. In other regions in Australia, P. cordata is regarded as an emerging new threat (Technigro Australia, 2015).
Perennial herbaceous emergent species (aquatic).
P. cordata belongs to the family Pontederiaceae, a small family of marginal aquatic plant species including Eichhornia. P. cordata is a rhizomatous perennial aquatic plant which grows erect to 120 cm. P. cordata has two types of leaves; a basal rosette of linear leaves which are normally submerged and emergent leaves which are stalked, (up to 60 cm) lance to heart shaped 6 – 22 cm long and 0.7 – 12 cm wide. Flowers form in inflorescences on the end of spikes that emerge from the main foliage. Each spike may contain several hundred flowers. Individual flowers are violet-blue in colour and are arranged in an elongated cluster along the spikelet. The upper petals have a yellow marking in the centre. Flowers are 4 -12 mm long and 10 – 16 mm wide and only open during the day. Fruits are single seeded, egg shaped, 4 – 6 mm long and 2 – 3 mm wide. Flower spikes droop following a period of flowering and the seeds enter the water body and are dispersed (Flora of North America Editorial Committee, 1993).
Biology and ecology
Pontederia cordata is a long lived perennial herbaceous aquatic species that roots within the mud substrate. The root system forms dense mats that cover the sediment. In North America (Florida), P. cordata flowers between March and November. P. cordata is recorded as having an aggressive growth habit, even in its native range (University of Florida, 1999). In Africa, the plant is regarded as being sterile with no fruits observed.
P. cordata grows in well saturated soils, at the interface between the aquatic and terrestrial environments, and in slow moving water bodies up to a depth of 40 cm (Q-bank, 2013). The species has been shown to form large monocultures in nutrient rich water bodies (Q-bank 2013). In the USA, Pontederia cordata is typically found growing in sediments of marshes, streams, lakes and ponds.
P. cordata does not have any tolerance to drought, it has a pH tolerance of between 6-8, it can tolerate low fertility, but has a low tolerance to shade. The plant grows well in fully exposed soils and can tolerate both freshwater and partial salinity (< 3 parts per thousand).
Uses and benefits
Young leaves can be eaten as salad greens. Seeds are also edible (Q-bank, 2013). The species is widely used as an ornamental plant species (Brickell, 1996).
Pathways for movement
Natural dispersal can be from seed and from rhizome fragments that are dislodged from the sediment and transported via mechanical methods. The root/rhizomes are easily spread within water following the disturbance of the population (Howard & Matindi, 2006).
Movement in trade
P. cordata is a popular ornamental plant grown in gardens and parks. The species is widely traded in the horticultural industry.
Effects on plants
The invasive nature of P. cordata has been recorded in both the native and some of the introduced range. In South Africa, the species is recorded to compete with indigenous riverbank plant species and crop species when it encroaches in irrigated fields (Invasive Species South Africa, 2015).
Environmental and social impact
In South Africa, P. cordata has been highlighted as forming dense stands which can block drainage canals and obstruct access to the edges of water bodies (Invasive Species South Africa, 2015).
Howard & Matindi (2006) detail that only mechanical removal has been practiced on invasive populations of P. cordata. The authors go on to highlight that care must be taken when disposing of root fragments.
Brickell C (1996) The Royal Horticultural Society A-Z Encyclopedia of Garden Plants. Dorling Kindersley, London.
Flora of North America Editorial Committee (1993) Flora of North America North of Mexico. : 18+ vols. New York and Oxford.
Howard GW & Matindi SW (2006) Alien Invasive Species in Africa’s Wetlands: Some Threats and Solutions. Nairobi, Kenya.
Invasive Species South Africa (2015) Pickerel Weed. http://www.invasives.org.za/invasive-species/item/311-pickerel-weed-pontederia-cordata.html.[accessed in March 2015].
Meert P (1988) Une Famille Nouvelle Pour La Flore Adventice de La Belgique: Les Pontederiaceae. Dumortiera 41, 1–3.
National Botanic Garden of Belgium (2015) Pontederia cordata Manual of the alien plants of Belgium. http://alienplantsbelgium.be/content/about-us. [accessed in March 2015]
Q-bank (2013) Comprehensive Databases of Quarantine Plant Pests and Diseases. http://www.q-bank.eu/ [accessed in March 2015]
Technigro Australia (2015) Pickerel weed (Pontederia cordata). http://www.technigro.com.au/documents/WW Pickerel weed.pdf. [accessed in March 2015]