whorled marshpennywort (Hydrocotyle verticillata)
Hydrocotyle verticillata is a perennial herb with creeping stems. It is reported to be perennial.

Overview
Hydrocotyle verticillata is a perennial herb with creeping stems. It is reported to be perennial.
Origin and habitat
Sources differ in describing its native range: it is reported from the Americas, extending from the United States to Argentina, Chile, and the Caribbean, while other accounts describe it more broadly as pan-American or as occurring in North and South America and the West Indies. It inhabits moist to waterlogged environments, including marshes, bogs, wet grasslands, flood zones, and the margins of ponds, lakes, streams, and rivers; fully submerged growth is uncommon in natural habitats. Its native range is reported to include temperate and subtropical regions.
Characteristics
The leaves are reported to be pale green and round, with slightly notched margins, and are held like umbrellas at the ends of long petioles; submerged leaves are usually smaller. The inflorescences are reported to have multiple whorls, with white-petaled flowers grouped in umbels.
Light
Sources differ on light requirements: at least moderate light is indicated, while some aquarium-growing information recommends high light and reports that stronger lighting supports growth.
Watering
Hydrocotyle verticillata suits continuously moist, marshy, or waterside conditions and can also be grown in aquariums, although fully submerged growth is uncommon in its natural habitat.
Temperature and dormancy
With few sources, the reported temperature range is about 15 °C to 25 °C.
Growing medium and mounting
For aquarium cultivation, it is reported to prefer a good substrate; unwashed medium-grained sand covered with fine gravel can be used.
Feeding
For aquarium cultivation, carbon dioxide supplementation is reported to be possible.
Common problems
In aquariums, growth may be very slow; the delicate stems and roots can cause plants to be pulled from the substrate when sludge is removed, and long-term maintenance under fully submerged conditions may be difficult. Aquarium cultivation is reported to be unsuitable under excessively hot conditions, and some tropical aquariums may therefore be unsuitable.
Identification
Hydrocotyle verticillata is reported to have creeping stems with long internodes and round, umbrella-like leaves; compared with Hydrocotyle vulgaris, it has relatively long internodes and petioles and an inflorescence with more whorls.
Photos



Sources
- Wikipedia (en): Hydrocotyle verticillata — CC BY-SA 4.0 · link
- Wikipedia (de): Amerikanischer Wassernabel — CC BY-SA 4.0 · link
- GBIF descriptions: Manual of the Alien Plants of Belgium; Database of Vascular Plants of Canada (VASCAN); Catálogo de P — per dataset · link
- USDA PLANTS Database: Hydrocotyle verticillata — Public domain (US Government work) · link