A year ago, I wrote a short blog about Pennywort after sampling a drink I bought at a local Asian market. Pennywort showed up in my world again a few weeks ago during a visit to Tres Rios Wetlands in south Phoenix, where white pelicans and great blue herons are some of the many charismatic avian residents. To my surprise, one of the dominant plants floating around the edges of the ponds there is a close relative of the popular edible and medicinal Pennywort, also known as Gotu Kola in medicinal plant lore. Even more surprising, this species seems to be relatively new to Arizona! Here is what I've learned so far:
Hydrocotyle umbellata, commonly known as Manyflower Marsh Pennywort, is an aquatic emergent that grows in slow moving water, marshes, ponds and in some regions, lawns. The plant is broadly established in southern California and in Texas, as well as throughout the southeastern and eastern states up to Nova Scotia, Canada. Large populations are growing in ditches and ponds at City of Phoenix Tres Rios Wetlands, a managed wetland project that uses treated effluent from the nearby 91st Avenue Wastewater Treatment Plant. The bright green floating mats of Pennywort leaves are clearly visible in recent images on Google Earth.
Previously collected specimens near this site and at the City of Phoenix Rio Salado Habitat Restoration Area demonstration wetlands, about ten miles east of Tres Rios, were incorrectly identified as Hydrocotyle verticillata, a closely related species. The two species are most easily distinguished by the the different kinds of flowering stalks: H. umbellata has "umbels," shaped like tiny umbrellas; H. verticillata has "verticels," which are vertically arranged on a slender spike. Both species have round, glossy, peltate (like a lily pad), leaves with ruffled edges. The plant spreads from submerged stems rooted in mud to create extensive floating mats along edges of ponds at Tres Rios wetlands.
No one is certain how it so recently appeared in Arizona, although it could have been here all along and nobody noticed. This is unlikely, however, since botanists have been scrutinizing the region for more than one hundred years. More likely, the plant may have been introduced as part of wetland restoration efforts along the Salt River. It is also possible that Pennywort was introduced by migratory birds that carry mud and seeds on their feet.
Keep your eyes peeled for other populations of this charismatic and opportunistic wetland species!
Like the Asian Pennywort, this one is also edible and may even increase your memory skills.
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