Ludwigia helminthorrhiza

Ludwigia helminthorrhiza is distributed in the American tropics, from southern Mexico to Paraguay. It mainly grows as floating plant with long stems in the shallow zones of different waterbodies, but also emersed as a creeping plant whose stems lignify a bit. It is not frequently found in trade but is often cultivated in botanical gardens.

An especially striking characteristic of this species are its densely growing, sometimes reddish floating leaves and its white, spongelike, spindle-shaped up to 2 cm long breathing roots. These so-called pneumatophores inspired this plant's scientific name (helminthorrhiza: "worm-shaped root"). Under favourable conditions, it will develop flowers with five white petals with a little yellow on their bases.

This strikingly decorative plant needs lots of light, and its long, ramifying, fast-growing stems need a lot of space, which limits its use as a floating plant for aquaria or paludaria. It will react very positively if it can root in a substrate rich in nutrients. During the warm season, this Ludwigia can also be cultivated outdoors in a sunny spot, e.g. planted in a pot that's placed in the garden pond, or in mobile containers. L. helminthorrhiza is easier in cultivation when kept emersed, and it flowers more readily then.