Water cabbage, or Rorippa aquatica, is a small amphibian plant found in the central and southern parts of the USA in the mud on the edges and in shallow water of springs, lakes, bogs, ditches and rivulets. It prefers clean, slow-flowing waters and is a rather rare plant in nature.
R. aquatica has long been cultivated as an aquarium plant, and it can sometimes be found in trade under its former name Armoracia aquatica. It is also known under the synonym Neobeckia aquatica. Rorippa aquatica differs from other Rorippa species like e.g. Rorippa amphibia, which is also found in Central Europe, by white instead of yellow flowers, among other characteristics.
Depending on the conditions it is grown in, R. aquatica can appear rather different. Submersed or non-flowering emersed plants form around 10 cm high leaf rosettes or upright stems with alternate leaves. The leaves may have a deeply incised margin and look almost pinnate with narrow tips, or they may be whole, with a coarsely serrate margin. Emersed plants with flower stalks and infrutescence can grow to a height of around 70 cm.
Water cabbage is a good foreground plant in the aquarium due to its relatively low growth. Relatively low temperatures of 20 to 25 °C are of advantage, as are moderate to high light and a substrate rich in nutrients. This plant is not very demanding, but grows very slowly even if given perfect conditions. It reproduces mainly by adventitious sprouts on the stem of broken-off leaves that remain floating at the water surface for propagation purposes.
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