Introduction to the Cryptocoryne genus (fam. Araceae)

by Xema, of Spain
 Photos by Xema, and Roland Seah of Singapore
Aquarticles

Introduction
Cryptocoryne are some of the most popular plants kept in aquariums, but are also the most unknown and truly underestimated.

These plants are cultivated in their emerged state and reach the hobbyist in this form. After introduction to the aquarium the emerged leaves give way to submerged ones by a specific melting typical of this genus. Observing this phenomenon most hobbyists think that the plant is dying, and they get a nice surprise a few weeks later when the plant reappears. But they are often considered dead and thrown away. This whole process is typical of cryptocorynes, not only when changing from emerged to submerged form, but also when sudden environmental changes occur, such as a variation in lighting or a decrease in the concentration of CO2…. this is what we call "crypt melt" - a quick response from the plant to these new conditions. Its symptoms are easily observed - tiny holes on the leaves that eventually grow in size as the whole leaf literally disintegrates. There is nothing we can do here but wait for new leaves to grow.

'Crypt melt' in Cryptocoryne wendtii

There are 58 known species of Cryptocoryne.This genus has not been widely researched and there are probably many more species to be discovered by rainforest botanists. They are widely spread, from India to New Guinea, and including places like Vietnam, Malaysia and Indonesia.The number of known species has increased considerably in the last few years, thanks to chromosomal research by Neil Jacobsen, who proved varieties were in fact either new species or members of new similar groups, such as crispatulas and cordatas.

Cryptocoryne are basal growth, herbaceous perennial plants, They are members of the Areceae family, many of which are well known to hobbyists, such as anubias, or pistias, and many others that are well known as houseplants.

The genus was first described by Fisher, 1828. The word Cryptocoryne comes from the Greek word Krypto (=hidden) and Koryne (=stick or thug), referring to the hidden (by the basal wall) spadix.

Photo linked from http://bbs7.as.wakwak.ne.jp/15309/1106398372.jpg

The spadix, a flowery structure typical of the family, is a 'stick,' which contains the male and female reproductive organs. The stamens are located in the top part of the spadix, and the stigmas in the bottom part, near the chamber.

This cavity is called the kettle, inside of which the spadix can be found alongside the producers of pollen and eggs, as well special cells which create colours in order to attract insects within this chamber so that pollination can take place. The fruit is produced by the ripening of the pastilles, creating a segmented seed capsule.

An idealised flower structure of Cryptocoryne (in Spanish)

Due to the large number of varieties of some species (e.g. wendtii), the only way to identify the particular species is to observe the bloom.

There is little information on these species, but due to their similarity to a well-known indigenous genus (Arisarum vulgare), we may assume that the pollination technique is very similar. An insect is lured by the perfume, but because of the valve it cannot escape, therefore provoking pollination during its struggle.

Cryptocoryne in the wild
Most of the easily kept and available species come from the island of Sri Lanka, including Cryptocoryne wendtii (varieties and hybrids), C. walkerii (= C. lutea), C. undulada, and C. becketii (including both the triploidic "petchii" as well as the diploidic forms.). These grow in small streams in soils of various types (sand, clay, rotten leaf deposits, etc.) and mostly in soft acidic waters.

Partially underwater Cryptocoryne wendtii

Recently some new species have been introduced to aquarists, indigenous to Malaysia and Indonesia, all of which are relatively easily kept in aquariums, including Cryptocoryne cordata and ciliata (especially). Others come from Sumatra and Borneo, such as C. pontederiifolia, some varieties of cordata, and C. crispatula and its varieties.

Totally underwater Cryptocoryne griffithii

Totally emerged Cryptocoryne pontederiifolia

As in Sri Lanka, most of these species grow by small streams in the rainforest (as well as on the surroundings during the wet season) in both man-made and natural water channels. Waters are soft and acidic, and soils vary according to species.

Cryptocoryne in aquaria
Cryptocorynes are very popular with hobbyists. For advanced hobbyists, those available in local stores are easy to keep. However, for the beginner any crypt can be tricky to keep alive, mainly because of lack of knowledge. As mentioned above, crypts are well known because of their melting, a temporary phase due to environmental adaptation. Once this is overcome, we can enjoy them for many years without any particular needs.

Like other plants, crypts need light and nutrients in order to grow and develop their full beauty. Therefore, any aquarium worthy of them must be equipped with a more than adequate light. But quality of light is just as important as quantity. Like most plants, they will adapt to a high spectrum of light. Even though they are considered low-light plants, they can be kept in any highly lit aquarium. Technically, we may use fluorescent lights from 4000 to 10000ºK with no problem, choosing more from a personal point of view - light colour preferred, etc. Other systems such as HQI metal halide and HQL halogen may also be used.

Another factor to be considered is the soil. Like most basal growth plants, cryptocorynes will of course grow healthier and more vigorously in highly nutritious soils. Typical neutral sandy soils will prove of no use in order to obtain this plant's full beauty. A good soil, with a noticeable quantity of clay and organic compounds, covered with a thin layer of fine sand, is a must to obtain full growth.

CO2 is of vital importance if we wish to keep aquarium plants, and of course crypts need it as well. A continuous flow is required at all times. CO2 is the main source of carbon for our plants, and since the aquarium water will be soft and slightly acidic they may not extract this element directly from the carbonates in the water. Macronutrients (nitrogen, potassium and phosphates) are also important. If we have highly nutritious soils, the need for these macronutrients is not so acute, allowing us to use smaller dosages than if we had faster metabolic plants. Even so, we must have all fertilisation techniques well in hand, in order to avoid outbreaks of algae.

Cryptocoryne wendtii

After all this, we may say that a crypt aquarium needs no more equipment than an average planted one. Pay special attention to the soil, and always ensure an unchanging aquarium environment, since sudden changes in conditions are these plants' worst enemies.

For those that find this genus truly alluring, there is also the possibility of keeping crypts in their emergent state….but this issue needs a whole chapter to itself.