Hydrocotyle sibthorpioides, or lawn pennywort, is a low-growing creeping plant native to the Asian and African tropics, which has been introduced into many of the world's warmer climates. It is highly adaptable and can live on dry land as well as in waterbodies. It is considered an invasive weed in lawns, boggy areas and on the banks of small rivers and rivulets in many regions.
In trade, it is often sold under the name "Hydrocotyle maritima". However, in botanic literature (e.g. "Flora of China"), the name H. maritima is not used as a synonym of H. sibthorpioides, but of another species, namely Hydrocotyle ramiflora. The trade name "H. maritima" is also used for another pennywort used in aquarium (see Hydrocotyle cf. tripartita).
The leaves of H. sibthorpioides are similar to those of Brazilian pennywort (Hydrocotyle leucocephala) but are a lot smaller (between 1 and 2 cm wide). The shoots of H. sibthorpioides, like those of H. leucocephala, grow above the ground - another thing the two species have in common. The shoots of whorled pennywort (Hydrocotyle verticillata),however, also grow as rhizomes inside the substrate.
In the aquarium, Hydrocotyle sibthorpioides is a demanding plant with a trailing growth. It requires lots of light to grow healthily and to reach its maximal size. For successful cultivation, CO2 injection is also a must (20-30 mg/l), as well as the regular supply of nitrate, phophate, iron and micronutrients. A high phosphate level helps to prevent green spot algae from forming on the leaves. Hydrocotyle sibthorpioides cannot be cultivated in tanks with low light and no CO2 supplemented as it would decay and die there. In strongly lit tanks and abundant CO2 and nutrient supply this species may develop into a very fast grower.
Propagating Hydrocotyle sibthorpioides isn't difficult at all as it throws many lateral shoots, which can be cut off and re-planted, as with all stem plants. Emersed cultivation,e.g. outdoors during the warm months, you can get a large number of cuttings for your tank, as the plant grows even faster when cultivated above the waterline. In that case, small white inconspicuous flowers and green infrutescences are likely to appear, too.
This pennywort also grows as terrestrial plant on moderately moist soil without any problems but rather like a weed, which makes it an ideal ground cover for brightly lit terraria and paludaria and even as potted plant for brightly lit windowsills.
Hydrocotyle sibthorpioides is a wonderful fore- and middleground plant in the aquarium. Its very special, light greyish green colour makes it a beautiful contrast to other foreground plant. It can grow quite densely and also upwards, which makes regular trimming necessary to maintain its beautiful form. When planting, just place some shoots in the middle of the area you want it to grow, weigh them down with some smaller pebbles, and they will establish there. After planting, H. sibthorpioides will grow slowly for some time, but after a while its growth will speed up, and the plant may require trimming at regular intervals so no neighbouring plants are overgrown.
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