About the Corkscrew Vallisneria
Species Type: Freshwater Plants
Category: Substrate Rooted
Care Level: Very Easy. Adaptable, will tolerate soft or hard water, low light, very minimal or no additional fertilization. pH 6.0 to 8.0 and GH up to 20 degrees/350ppm.
Origin: Recorded throughout the tropical and sub-tropical regions. Plants often inhabit nutrient-rich stagnant or slow-moving waters having a substrate of mud.
Vallisneria has been a popular and frequently-seen aquarium plant since the earliest days of the hobby. There is considerable confusion over the nomenclature of this genus [see comments below], and several different "species" and varieties may be encountered in the literature; one may therefore find the same plant under various names.
The tightly-twisted "corkscrew" form remains much smaller than other varieties, the 5-10mm wide leaves attaining up to 30-50 cm (12-20 inches). Vallisneria plants are not particular about the composition of the substrate and will grow very well in plain gravel provided liquid fertilizer is regularly added to the water. They readily assimilate carbon from bicarbonates (as opposed to carbon dioxide) and thus do exceptionally well in harder water; some can even tolerate brackish water that is not too high in salt. Several aquarists report that Vallisneria plants do not respond well to the use of liquid carbon supplements [such as Seachem's Excel and API's CO2 Booster] which are composed of the toxic chemical glutaraldehyde and water, and the plants completely melt.
Vallisneria species are quite similar in appearance to Sagittaria. The leaves of the latter are usually darker green and more stiff, pointed, and have a different vein structure; their roots are whiter and thicker than Vallisneria. Some aquarists hold that the two genera do not fare well in the same aquarium.
Vallisneria is distributed in all tropical and subtropical areas worldwide; in some places, such as the continental United States, they extend into the temperate zone. All species are dioecious, having male and female plants that both produce flowers. The female flowers grow on long scapes and float on the surface; male flowers are produced at the base of the male plant and become detached and float to the surface and open. The water then carries the pollen to the female flower. Seeds are not produced in aquaria, and the plants spread by numerous daughter plants that arise from runners. These daughter plants may be left to form an extensive mat of plants or separated once they have developed several leaves and roots and planted in another location.
The "corkscrew" variety is frequently seen under the name Vallisneria spiralis forma tortafolia, and a few taxonomists have elevated this form to a distinct species, V. tortissima. A near-identical plant differing only in the structure of the flower and in having narrower (3-5mm) leaves is Vallisneria americana var. biwaensis.
The Hydrocharitaceae family of floating and submersed aquatic plants, commonly called the Tape Grasses, contains both marine and freshwater plants found on all continents in the tropical and temperate zones. With the exception of the Asian genera Blyxa and Ottelia, the plants in this family tolerate very hard water. All species are flowering, the marine species being pollinated submersed and the freshwater on the surface; pollen is dispersed by water except for Stratiotes and a few species in Ottelia that are insect pollinated. There are 18 genera, several containing plants commonly seen in aquaria.
The genus Vallisneria was named in honour of Antonio Vallisneri (1661-1730) by the "Father of Taxonomy" Carl Linnaeus (1707-1778) and he described the species Vallisneria spiralis in 1753. The name "spiralis" refers not to the leaf shape but to the long spiralling stalk of the female flower. The common name of V. spiralis is "Straight Vall" because of the straight ribbon-like leaves [see the first photo above]. This original form can grow to 120 cm (4 feet). There are several variants, natural and hybrid, with a variety of leaf forms.
The confusion over the species in this genus has largely occurred due to the difficulty of identifying them by anything other than the flower structure. The leaves of plants in the same species can appear very different depending upon growing conditions, both in nature and in the aquarium. As previously noted, the spirally-twisted leaf form of V. americana is basically identical to the screw-like twisted leaf of the corkscrew form of V. spiralis.
Studying the flower of each species is complicated by the plants having distinct female and male flower forms that occur very rarely in nature and are therefore difficult to obtain. Extensive research detailed in published studies in 1982 by two independent botanists, R.M. Lowden and Christopher D.K. Cook, came to the same conclusion: the genus Vallisneria holds only two species, V. americana and V. spiralis, and both have two varieties. The relevant taxonomic criteria to determine the true species turned out to be the arrangement of the carpels in female flowers and the number of stamens in male flowers. Since the vast majority of aquarists will not be familiar with flowering Vallisneria, detailing these distinctions here would serve little purpose, but there is a summary in Kasselmann (2003) for those who are interested. The plant endemic to Australia was determined to be Vallisneria nana by Jacobs & Frank (1997).
More recent work (Les, et al. 2008) using phylogenetics has resulted in 12 species being identified by molecular data, and an additional 2–3 species by morphological differences within groups that were invariant at the molecular level. Two new Vallisneria species (V. australis, V. erecta) are formally described in the same study.
Cook, Christopher D.K. and Ruth Luond (1982), "A Revision of the genus Nechamandra (Hydrocharitaceae)," Aquatic Botany 13, pp. 505-513.
Kasselmann, Christel (2003), "Aquarium Plants," English edition, Krieger Publishing Company, Florida.
Les, Donald H., Surrey W. L. Jacobs, Nicholas P. Tippery, Lei Chen, Michael L. Moody, and
Maike Wilstermann-Hildebrand (2008), "Systematics of Vallisneria (Hydrocharitaceae)," Systematic Botany, volume 33(1), pp. 49-65. Available online: http://www.ingentaconnect.com/search/download?pub=infobike%3a%2f%2faspt%2fsb%2f2008%2f00000033%2f00000001%2fart00008&mimetype=application%2fpdf
Lowden, R. M. (1982), "An approach to the taxonomy of Vallisneria L. (Hydrocharitaceae)," Aquatic Bot. 13, p. 293.
Rataj, Karel and Thomas J. Horeman (1977), "Aquarium Plants," TFH Publications Inc.
Ideal position in aquarium
Mid-ground in larger tanks, background in small tanks.
Minimum Tank Suggestion
Ideal water parameters for Corkscrew Vallisneria
Medium hard to hard, very slightly acidic to basic, temperature 20-28C/68-82F. Grows better in basic, harder water.