The genus Hydrocotyle Linnaeus
and Hydrocotyle americana Linnaeus
The words or terms in red
(actually dark orange) in the text are defined in a
The genus Hydrocotyle Linnaeus
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
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
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
They often forms large dense colonies of plants in muddy soil or shallow water.
Some botanists split the species in two varieties :
- Hydrocotyle americana L. var. flexicaulis Michx.
- Hydrocotyle americana L. var. gracilis Michx.
In classical Greek,
(hydro) is a prefix referring to water and
(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
Some of the vernacular names of
Hydrocotyle americana are American marsh pennywort, marsh pennywort,
water ivy, navelwort. The French vernacular name is
Hydrocotyle americana is easy to identify by its :
- humid habitat;
- rounded leaves with rounded lobes;
- white to greenish flowers in small clusters;
- leaf stalk attached to base of the of a cleft leaf.
- round to broadly oval
- up to 2 inches wide;
- cleft at the base with the leaf
petiole attached at base of
the leaf cleft;
- the petiole pale green to pale reddish green, terete, glabrous,
rather fleshy like the stems, up to 5 cm in length;
- the upper surface is yellowish green to dark green and glabrous;
- with 6 to 10 shallow well-rounded
- in the leaves axils, in an
unbranched and flat umbel
about 1/2 inch across and that
has with 2 to 7 (at times up to 12) flower-groups per umbel
(and no umbellets);
- sessile or nearly so;
- inconspicuous, below the leaves;
- white or greenish yellow;
- 1/16 to 1/8 inch across;
- with 5 petals;
- with 5 stamens;
- with a divided style;
- blooming in July and August in my area, 25 km north of Montréal.
The achenes can float on water, distributing this plant to new locations.
- dry achenes;
- splitting into 2 round seeds with strong vertical ridges.
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
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
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