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Family: Alismataceae

Common Name: Uruguay Sword

Origin and Habitat: Southern Brazil, Uruguay, northern Chile and northern Argentina. Occurs in rivers and streams having moderate currents and substrates of gravel and loam. Water parameters varied in pH from 6.2 to 7.11 with no discernible hardness (Kasselmann, 2003]. Water temperatures in the habitat rivers are somewhat cooler, especially during winter.

Ideal position in aquarium

A good specimen plant in larger tanks.

Lighting requirements

Moderate to bright.

Growth rate


Minimum Tank Suggestion

Best in deeper tanks (24+ inches).

Water parameters for Uruguay Sword

Soft to medium hard (< 18 dGH), acidic to slightly basic (pH 6-7.5), optimum temperature 18-24C/64-75F.


This species is polymorphic, meaning that it occurs naturally in more than one form. Leaves may be dark olive green, reddish-brown, even blackish-red. Kasselmann (2003) states that some are undoubtedly hybrids. The plant often seen under the name Echinodorus horemanii [described by Rataj in 1970] is probably not a distinct species but the dark leaved form [Haynes & Holm-Nielsen, 1994; Kasselmann, 2003; Lehtonen, 2007].

Leaves will attain 30-60cm/12-24 inches or more, and are narrow (3-4 cm, usually less) with a slightly undulating margin, which when combined with the darker colour will create a nice contrast in a larger aquarium. Slightly acidic water, temperatures within the optimum range indicated, and a nutritious substrate (or regular fertilization) will encourage good growth and darker colouration under moderate light. Inflorescences will be formed, with 2 or 3 adventitious plants on each whorl (node). Under good conditions, this species forms a large number of leaves, up to 100 within a few months.

As with the majority of species in this genus, E. uruguayensis can be cultivated emersed as well as submersed, but it occurs predominantly in water (submersed cultivation), rarely emersed in nature. As with all species in the genus, aquatic leaves will be quite different from emersed leaves, in shape, size and texture. Newly-purchased plants may have been propagated emersed by nurseries and if so will have leaves more oval-shaped than the submersed form of lanceolate (long and narrow); when grown in the aquarium the developing submersed leaves will be long and lanceolate, and the older leaves will yellow and should then be removed.

The species was described by Arechavaleta in 1903; the species epithet is Latin and means originating from Uruguay.

Some of the most beautiful and useful plants for the tropical aquarium are found among the Echinodorus, a genus distributed in the tropical and sub-tropical regions of the Americas from the lower United States down to Argentina; the two "African" species of Rataj are almost certainly erroneous (Kasselmann, 2003). The genus name derives from the Greek echinos [hedgehog] and doros [pipe or hose] referring to the spiny fruit. The English common name "sword plant" comes from the general lanceolate shape of the leaf of most species and is generally used for all plants in this genus although other non-Echinodorus plants may sometimes appear under the name "sword."

Larger-sized species have a rhizome, whereas smaller species are stoloniferous. All species are perennial or annual aquatic or marsh plants found in boggy flood areas or along the banks of stagnant or slow-flowing waters. Except for the very few species that are permanently submersed, Echinodorus plants spend half the year emersed (when they flower) and the remainder submersed during the flood season. Leaves arise in a rosette and can be very variable not only between emersed and submersed forms but also when cultivated under different conditions. Correct identification often requires study of the flower. Inflorescences (flower stalks) are formed in all species; when grown permanently submersed in the aquarium most species will not flower but adventitious plants (daughter plants) will develop from the nodes on the inflorescence.

Confusion exists over the number of species, and many have been known under different names. In his earlier revision of the genus, Rataj (1975) listed 47 species. A major revision by the botanists R.R. Haynes and L.B. Holm-Nielsen (1994) lists 26 species. In 2004, Rataj increased the number of species to 62. More recent work by Samuli Lehtonen--incorporating cladistic analysis using morphological data--has proposed 28 valid species (Lehtonen, 2007).

Haynes & Holm-Nielsen (1994) consider E. uruguayensis as the single species that includes E. osiris as well as E. horemanii and E. africanus. Kasselmann (2002) suggests that E. osiris may be a natural hybrid and thus a distinct species. Four Echinodorus species--E. osiris, E. uruguayensis, E. opacus and E. grisebachii--have been observed growing together in southern Brazil, supporting this contention. Lehtonen (2007) also proposes E. osiris as synonymous with E. uruguayensis, and if this is accepted we should be prepared for significant re-naming within the genus. As noted earlier, E. horemanii was described as a distinct species by Rataj in 1970, and in his 2004 revision of the genus he notes differences in leaf structure in support of his contention; but others remain in agreement that this is the dark-leaf form of E. uruguayensis and not a distinct species.


Haynes, R.R. and L.B. Holm-Nielsen (1994), "The Alismataceae," Flora Neotropica, Vol. 64, pp. 1-112.

Kasselmann, Christel (2002), Aquarium Plants [English translation by Ulf Kotlenga].

Lehtonen, Samuli (2006), "Phylogenetics of Echinodorus (Alismataceae) based on morphological data," Botanical Journal of the Linnean Society, 150, pp. 291-305.

Lehtonen, Samuli (2007), "An integrative approach to species delimitation in Echinodorus (Alismataceae) and the description of two new species," Kew Bulletin Vol. 63, No. 4, pp. 525-563.

Lehtonen, Samuli and Leena Myllys (2008), "Cladistic analysis of Echinodorus (Alismataceae): simultaneous analysis of molecular and morphological data," Cladistics, Vol. 24, No. 2 (April 2008), pp. 218-239.

Rataj, Karel (2004), "A New Revision of the Swordplant Genus Echinodorus Richard 1848 (Alismataceae)," Aqua--Journal of Ichthyology and Aquatic Biology, Special Publication No. 1, March 2004.

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