Cryptocoryne cordata var. cordata

The heart-leaved water trumpet, Cryptocoryne cordata, is a very variable species with many forms, distributed from Southern Thailand across the Malay Peninsula to Sumatra and Borneo. Various plants that were formerly in part regarded as separate species are counted as belonging to it. Today, after many years of field research, Cryptocoryne experts distinguish four varieties of C. cordata:

• Cryptocoryne cordata var. cordata (mainly West Malaysia),
• C. cordata var. siamensis (Southern Thailand to beyond the border with Malaysia; this includes, among others, the former C. blassii and C. siamensis),
• C. cordata var. diderici (Central Sumatra; formerly called C. diderici),
• C. cordata var. grabowskii (Borneo; the former C. grabowskii as well as C. cordata var. zonata).

Cryptocoryne cordata var. cordata includes the plants on which William Griffith based his description of the species C. cordata (published 1851). They are widespread on the Malay Peninsula in West Malaysia and also still occur in the extreme south of Thailand. They typically grow mostly submersed in soft, acidic water in peat swamp forests.

As an aquarium plant, the variety cordata plays no great role. In Germany it was in part in cultivation under the erroneous name Cryptocoryne griffithii (a different species). It is considered difficult to cultivate; a soft, acidic environment is recommended. The most common Cryptocoryne cordata forms in the aquarium hobby, best known of all the “type blassii”, on the other hand, are quite undemanding. These plants were formerly likewise counted as var. cordata, but are today counted as var. siamensis. This has only been distinguished as a separate variety since 2010 and occurs further north in Southern Thailand in waters with a limestone bedrock and relatively hard water.

The leaf blades of Cryptocoryne cordata var. cordata are up to about hand-sized and broadly ovate with a heart-shaped base (cordata = “heart-shaped”). The upper side of the leaf is green, the underside pale green to reddish, sometimes with red leaf veins. The spathe (inflorescence bract) can be over 20 cm long and has a light yellow limb. The chromosome number is 2n = 34. The variety cordata forms with Cryptocoryne griffithii the natural hybrid Cryptocoryne × purpurea nothovar. purpurea.

The variety siamensis differs from var. cordata in having ovate to narrowly ovate, not heart-shaped leaves, a spathe only approx. 10 cm long and a chromosome number of 2n = 102.

(For more, see “Culture”)