Willisii

Two different plants have been sold as Cryptocoryne willisii, and Flowgrow documents both halves of the confusion. Its Cryptocoryne undulata page carries "Cryptocoryne willisii Engler ex Baum (1909), non Reitz (1908)" among that species' own synonyms, while the legitimate use of the name belongs to Cryptocoryne x willisii Reitz, a complex of natural hybrids from the central highlands of Sri Lanka around Kandy. This entry is the second plant: the small, slow, ground-covering crypt, not the taller brown-leaved undulata.

Flowgrow has no page for the complex as a whole, only for its forms, so this entry follows the one it files as 'nevillii'. That is the plant the hobby sold for decades as Cryptocoryne nevillii, until Niels Jacobsen showed in 1976 that it belongs among the x willisii hybrids and that the true C. nevillii is an unrelated species. The published figures are 22 to 28 °C, pH 4.5 to 8, carbonate hardness 1 to 18 dKH, light from low to high, easy, slow. The narrow-leaved 'lucens' form of the same complex publishes identical figures and has its own entry in this catalog; the two differ in leaf shape rather than in care, and Flowgrow says outright that they cannot always be told apart in cultivation.

This form is the one with shorter, oblong to lance-shaped blades. It spreads by underground runners into a low, even patch, and small specimens are easy to mistake for Cryptocoryne parva. We file it as a midground plant, following Flowgrow's first-listed use, though the same page also lists nano tanks, foreground and group planting. The 10 cm height is editorial: Flowgrow publishes no height row for the form, and the 20 cm submersed figure in its text describes the complex at large.