Cardamine lyrata vs. Hydrocotyle leucocephala

By Ron Finlayson
First published in "The Daphnian", Boston Aquarium Society, March 1999
Aquarticles

I recently purchased some Cardamine lyrata which was sold to me as a bunch plant from Uncle Ned's. At the time I was aware that this was a different, but similar plant to Hydrocotyle leucocephala, which I already had and use in a number of tanks. In this article I wish to compare the two plants in relation to their growth habits, uses and needs in the aquarium.

First Hydrocotyle leucocephala, commonly called Brazilian Ivy or Pennywort. Ivy is a good name for this plant, because that's how it grows. When purchased the plant is usually sold in bunches of 5-7 stems. You should either place the ends in the gravel at 1-2 inch spacing, wrap it around some structure such as a stone or driftwood or just let it float. No matter what you do, given the right conditions this plant will head toward the surface, and that's where it likes to be. I have planted H. leucocephala in the gravel only to have the lower leaves and stem disappear as the main plant heads toward the surface and the light.

Once this plant reaches the surface I have found that it really takes off. As it travels and branches across your aquarium the leaves will increase in size, will become a darker green, and may even flower as it has done many times for me- You will also notice that the plant will throw off little root systems at each leaf axis which will absorb those unwanted nutrients in your tank that cause unsightly algae blooms. These roots, sometimes extending down the the bottom of the tank are also attractive in their own way and create hiding places for any fry that might have blessed your aquarium. I regularly take top cuttings of this plant and use it at will in my aquariums.

H. leucocephala is a rewarding and undemanding plant in the aquarium. It is adaptable to various temperatures. I have grown it in my pond as low as 65o F and as high as 85o F. Although I have never grown this plant in real hard water above 7.8 gdh, I have grown it in soft water as low as 6.0 gdh. It also grows equally as well with or without CO2, but I do suspect it does enjoy having C02 around.

Second, Cardamine lyrata commonly called Japanese Cress. At first look it may be difficult to tell C. lyrata and H. leucocephala apart, both are any ivy type plant, both have a roundish leaf with a jagged edge and both are similar in color- green. These are different plants however and they grow, act and look different in the aquarium.

Upon planting my C. lyrata after purchase, I divided the bunch 5-7 stems, placing some in my 220 gallon aquarium that has CO2,   eight T8, 32 watt, 5000K lamps set on an 11 hour timer with the tank in front of a window which gives it early morning light. The rest of the bunch was placed in a 40 gallon breeder tank that has. No CO2, four T8, 32 watt, 5000K lamps set on an 11 hour timer but not in front of a window. Both tanks have soil in pots as well. What happened? The plants in the 40 grew very slow with small leaves and maintain rather than going nuts as I like.

The plants in the 220 went crazy, the total plant mass increased 100 fold in eight weeks, why? Partly because the light in the 220 was more intense, and partly because of the CO2. This plant really likes CO2 and will reward its caretaker with phenomenal growth. The pH in the 220 was approximately 6.7 and the temperature was a high 83o F. This would be a good plant for a Discus tank!

But how is it different from H. leucocephala? I found that even with CO2 the leaves of C. lyrata stay small. The plant does not travel right to the surface as does H. leucocephala, C. lyrata will instead form dense patches in one area almost like a brier patch, and spread from there. This gives the aquarist a number of different options for use in the aquarium. Now you can use this plant to create a dynamic effect in one location in your tank. The growth habits of this plant also lend itself to creating a number of hiding places for fry. I am presently using several large clumps throughout my 220 in the lower half of the tank. The contrast of the small round leaves intertwined with other plants is really neat.

Hope you consider giving both these plants a try in your aquarium. I have enjoyed both and think you will have the same experience.