The genus Hydrocotyle Linnaeus and Hydrocotyle americana Linnaeus

Remark The words or terms in red (actually dark orange) in the text are defined in a glossary.

The genus Hydrocotyle Linnaeus

aug_01_04c.gthmb can't be loaded. The genus Hydrocotyle is that of prostrate perennial plants; they are common aquatic or semi-aquatic plants. They have long creeping stems that often form dense mats, often in and near ponds, lakes, rivers, marshes and, for some species, in coastal areas by the sea. Their leaves are simple, kidney shaped to round, and their margins are scalloped. Their flowers are in clusters, and with indistinct sepals. Their fruits are elliptical to round with thin ridges and no oil tubes which is characteristic in the fruit of umbelliferous plants (the plants belonging to the Apiaceae family). In fact the Hydrocotyle genus was formerly classified in the Apiaceae family but it now has been put in the Araliaceae family.

The genus has between 75 and 100 species that grow in tropical and temperate regions worldwide, a few species have made it into the world of cultivated ornamental aquatics. In North America, on can find 12 species, on with two varieties, but only one species. Hydrocotyle americana (photography at right), is found in Québec.

Hydrocotyle americana Linnaeus

Hydrocotyle americana is native to North America. It is a creeping perennial plant, between 4 to 12 inches high, with very thin terete and glabrous stems; it roots from its stems nodes. The root system consists of masses of fine fibrous roots that can penetrate the soil or drift in the water from the stems. The plants are arranged in a small group of leaves and flowers attached by thin runner to other similar groupings. They often forms large dense colonies of plants in muddy soil or shallow water. Some botanists split the species in two varieties :


In classical Greek, υδρο (hydro) is a prefix referring to water and κοτυλοσ (kotulos) is a cup; the word Hydrocotyle would then refer to a water cup, apparently from the leaf shape.

As for the epithet it refers to the fact that Hydrocotyle americana is native to America, and the International Code for Botanical Nomenclature, Recommendation 82 E, recommends that epithets taken from geographical names should be adjectives and end in anum or some other latin adjectives endings.

Common names

Some of the vernacular names of Hydrocotyle americana are American marsh pennywort, marsh pennywort, water ivy, navelwort. The French vernacular name is Hydrocotyle d'Amérique.


draw_a.jpg can't be loaded. Hydrocotyle americana is easy to identify by its :





The achenes can float on water, distributing this plant to new locations.


Hydrocotyle americana is found in a variety of wet habitats, marshes, springs, swamps, open areas in humid locations, cliffs and ledges where wet by seepage or spray from waterfalls. It grows in sunny area or in partial shade.


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Hydrocotyle americana is found in southern Canada, westward to Minnesota, and southward to Pennsylvania. It is also found further south in the mountains to North Carolina and westward to Arkansas. The map shows the Canadian provinces and USA states where the plant can be found.


In Europe, Hydrocotyle americana is considered an invasive species. Considering its tendency to develop large colonies, it is surprising that this species isn't more common in North America than it is.

The attractive leaves of Hydrocotyle americana resemble those of the commonly called Nasturtiums (belonging to the Tropaeolum genus, not to the Nasturtium genus of the Brassicaceae family), introduced horticultural plants that are often cultivated in flower gardens.


The photos of the gallery were taken either with one of the following: Minolta DiMAGE 7, Canon PowerShot A530, Canon Xt Rebel, usually with the EF-S60mm f/2.8 Macro USM objective, Fujifilm A 610 and EPSON Perfection 1650 (scanner).

The title in the window shows the date when the picture was taken, i.e. jan_30_06... would mean that the photo was taken on the 30th of January, the 06 is for the 6th picture taken that day. The month, day and picture number might be followed by a letter which I use to identify the system used to take the picture.

Click on the thumbnails to get larger view. The original photos are usually in TIFF format, the photos shown are generally in JPEG format, often of dimensions one half (surface one quarter) for loading time reduction.

Stems, flowers, fruits

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