Echinodorus cordifolius

Creeping burhead, or Echinodorus cordifolius, is a very variable species distributed in the eastern and south-eastern parts of the USA to South America. Depending on the author, sometimes Echinodorus ovalis and E. fluitans are considered to belong to the species E. cordifolius, or as species in their own right.
E. cordifolius is mainly found growing emersed on marshlands, ponds or in the shallow water of lakeshores.
Typical forms of E. cordifolius, as they occur in the South of the USA, are high-growing plants with wide heart-shaped leaves. However, there are some populations with narrow-oval to lanceolate leaf blades.
Sometimes, plants sold as E. cordifolius that grow very large and have round heart-shaped leaves might really belong to the species Echinodorus floribundus (from the group of plants related to E. grandiflorus).
E. cordifolius is one of the oldest aquarium plants, and it is also known under the vernacular name radican sword or the synonym Echinodorus radicans.

E. cordifolius differs from E. floribundus in its inflorescence. The flower stalks of E. cordifolius start lying down soon after sprouting, and they always develop adventitious plants (the flower stalks of E. floribundus maintain their upright growth habit for a longer period of time), by longer peduncles (up to 8 cm) as well as by the form of the transparent patterns (pellucid areas) in the leaf tissue (in E. cordifolius: dots and dashes, in E. floribundus only dots).

E. cordifolius is or is not suitable for aquarium cultivation, depending on the population. Under intensive light, long-day conditions and an ample nutrient supply these plants tend to grow floating leaves and aereal leaves that grow out of the water, whereas the submersed leaves die off. In some forms of E. cordifolius, this does not take very long - these plants are only suitable for open tanks. Other aquarium populations are easier to keep submersed, though. Short-day conditions (a dark phase of over 12 hours in succession by night) and the removal of any long-stalked leaves are recommendable. Inflorescences with adventitious plants mainly form on plants that are cultivated emersed.

To be continued...