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Depending on the species available, pennyworts can be used outdoors, in cool, or tropical aquariums, even as bog plants. They are hardy, non-finicky plants in the proper-range setting, demanding only a little nutritive soil and moderate light.
Aptly named pennywort or umbrella plants for their appearance, Hydrocotyle are tough and fast growing, as long as you select the right species, tropical or temperate, for the job.
Classification & Species of Use To Aquarists:
Older works place Hydrocotyle as members of the parsley family Umbelliferae or Daucaceae. Modern systematic schemes place it in the Apiaceae, along with root vegetables such as the wild carrot and dill.
Note: there is a similar sounding, but very different aquarium plant called moneywort (Lysimachia nummularia) in the family Primulaceae, not to be confused with pennywort.
Alike in appearance is the oriental cardamine, Cardamine lyrata; look not to the leaves themselves, but to the stems to tell them apart. Hydrocotyles is joined mid-center, whereas cardamine is offset with side-shoots that are much longer.
Of the eighty or so species of Hydrocotyle there are but a handful that find their way into ornamental aquatics. The most common four species are so similar that without having specimens on hand to compare, they are hard to differentiate... Pay attention to the arrangement of leaves on differing length stems, how they're arrayed, and the arrangement and number of their flowers.
Hydrocotyle leucocephala CHAMISSO & SCHLECTHTENDAHL, 1826
Brazilian pennywort; a tropical species.
Synonyms:H. leucopetala, H. aquatica.
Natural Distribution & Ecology:Brazil.
Desc:Leaves more kidney or oval than lilypad shaped, with slightly serrated-edged margins. Long stems have leaves (more than one) growing alternately side to side, ultimately developing into floating forms. Floating leaves are slit with divisions to centers and ribbed with dark green veins; over time they develop long, flowing white root systems.
Hydrocotyle vulgarisLINNAEUS, 1753
Mediterranean or European marsh pennywort. THE common pennywort or umbrella plant in the west; a cool to cold water species that perishes in tropical waters.
Natural Distribution & Ecology: Europe, North Africa. This species is poorly adapted to permanent submerged aquarium existence. Does okay as an emergent terrarium, bog or cool water pondside potted plant.
Physical Description:Very similar to H. verticillata below, with the flower difference that is noted. A creeping main shoot gives rise to short (4-5 inches max.) stems each bearing a roundish, emarginated leaf that is not incised (cut in) to the center.
Hydrocotyle verticillata THUNBERG, 1798
Whorled umbrella plant.
Natural Distribution & Ecology: North and Central America, Caribbean. A creeping terrestrial, floating or aerial plant. Okay for tropical or cool water aquariums.
Physical Description:Round leaves mounted centrally on vertical stems up to six inches long that emerge independently from the bottom surface. Leaf blades are radiated with veins that extend to emarginated margins. Has flowers in groups of threes as opposed to the single umbellate stalked ones of H. vulgaris. Good for warm water (65-75 F.) aquarium foreground, bog and potted pond shore use in summer.
Hydrocotyle lemnoides BENTHAM, 1868
Natural Distribution & Ecology: Australia.
Physical Description:Unmistakable from other Hydrocotyle species with its strongly notched leaves supported on long thin shoots. Tiny flowers in groups of 4 or 5 are supported on collective delicate umbrella-like structures (umbels). Good for tropical aquariums and warm water ponds as submersed or floating forms.
A brief note regarding other Hydrocotyle species; there are several others that occur worldwide (5 in the U.S.) that might well prove of use to hobbyists. Keep an open mind.
Pests, Parasites, Disease:
Substrate/Soil:A mix of clay with some loam is preferable, though will live in gravel with just "fish fertilizer".
Light/Lighting (intensity, spectrum, duration): Natural or artificial light of half day duration, 20-40k lumens.
pH, KH, Other Chemical:Slightly acidic to alkaline (6-7.5), soft to medium hard water (2-15 KH).
Temperature Range:Variable; see species for requirements.
Species Kept With:Situations where pennywort is not shaded.
Trimming:Great for group plantings; looks too scraggly when spread out. Should have over-towering growth trimmed frequently (before covering the surface). Folks growing Hydrocotyle outdoors should take care to not let it invade their surrounding landscape. Pennywort is VERY invasive and difficult to eradicate (I've used selective bio-warfare, i.e. rust diseases, and had to Vapam areas to get rid of it). Dig out the area
From cuttings (trimmings planted), and seeds.
Typically sold in "bunches" or as a group in a "pot". Should be liberated from bands, weights, or "wool" and individually planted deeply in the gravel of the main/display system or in pots.
So you can see that success with Hydrocotyle is a matter of matching the available species with given conditions. There is a pennywort for all non-frozen pond, terrarium and aquarium applications. Try the Brazilian H. leucocephala or Australian H. lemnoides for foreground accent in your heated tanks. And be wary of the European H. vulgaris and north American H. verticillata for anything but cool water or terrarium applications.
With easy care, just suitably plant them and leave alone, yours may go from penny to silver-dollar size leaves.
Anon. 1972. The Brazilian pennywort. Aquarium Digest Intl. 1(2):16, 1972.
Anon. 1975. Brazilian pennywort- a versatile plant. ADI 3(2):22, 1975.
Baensch, Hans A. & Rudiger Riehl. 1993. Aquarium Atlas, v. 2. BAENSCH, Germany. 1212 pp.
Brunner, Gerhard. 1973. Aquarium Plants. T.F.H. Publications, NJ. 159 pp.
Osborne, Kevin. 1995. Pennywort. FAMA 8/95.
Ott, Gerhard. Undated. Two species of Hydrocotyle for the aquarium. ADI Plants #32.
Rataj, Karel. 1979. Culturing pennywort Hydrocotyle vulgaris. TFH 7/79.
Riehl, Rudiger & Hans A. Baensch. 1987. Aquarium Atlas, v. 1. MERGUS, Germany. 992 pp.
Roe, Colin D. 1967. A Manual of Aquarium Plants. Shirley Aquatics, England. 111 pp.
Stodola, Jiri. 1967. Encyclopedia of Water Plants. T.F.H. Publications, NJ. 368 pp.
Tomey, William A. 1968. Hydrocotyle leucocephala. The Aquarium 10/68.
1) An aquarium shot of the pennywort look-a-like, Cardamine lyrata. Note more extensive side shoots.
2) The moist terrestrial north American H. verticillata growing aerially in Florida.
3) A drawing from a science text illustrating the umbels, the arrangement of flowers in this group.