Cryptocorynes are plants from the monocotyledon family Araceae that live in many parts of Southeast Asia, from India to New Guinea and the Philippines as well as Southern China and Sri Lanka.

In the wild, the plants grow in streams and rivers, swamp forests and sometimes artificial waterways. For part of the year, many plants will be totally submerged, but in the dry season, they will grow as fully emergent marsh plants. During this time, many Cryptocorynes take the opportunity to flower, putting forth their showy and colourful inflorescenes. The watertight tube of the Cryptocoryne inflorescence also allows the plant to flower even when the foliage is fully underwater, as the opening (or throat) of the tube opens above the water surface to allow pollinators access to the kettle (which lies underwater) where the pollen and pistils are housed. Species that often flower whilst submerged include C. crispatula, C. aponogetifolia and C. cordata. However, most other cryptocrynes will only bloom when the entire plant is grown emmersed.

Compared to the classical planted tank approach that frequently employs expensive CO2 injection systems and filters, emmersed cryptocoryne culture offers a more hassle-free option. There are also some cryptocoryne species which are virtually impossible to grow submerged. Collections of emmerse cryptocorynes play a vital role in preserving and propagating many rare species, in particular via the production of fruit and seeds.

In addition, some cryptocorynes can only be conclusively identified via the inflorescene.

What do cryptocorynes need to grow emerged?

The key requirements for growing emerged cryptocorynes are:

Enviroment humidity

The habitats where cryptocorynes grow are typically tropical rainforests, where frequent rain and ample shade from jungle trees create an environment of high relative air humidity (at least 70%),

Soil (substrate)

The substrate provides both physical support for the plants as well as a source of nutrients. Cryptocorynes are found in different natural substrates: clayed soils, muddy soils and leaf litter substrates. In choosing a substrate, one should imitate the composition of the original soil in which the species grows.

The soil for growing emerged cryptocorynes should have a suitable pH for each species (acid, in general). It must be able to retain water and at the same time to offer good drainage. The size of the soil particles is not very important, but personally I prefer a half-size grain.

Several sort of substrates:

Silica sand; this is an inert substrate that contributes no nutrients to the plant; it provides only physical support to the plant roots. Sand does not retain much water, only a small amount of water is retained within the pores of the sand via capillary action. Thus, sand is usually not used alone, but in combination with other substrates or additives. It has a neutral or lightly acidic pH.

Compost; gardening markets usually supply large quantitis of compost. Compost is the result of the artificial mixing of vegetable litter like leaves, branches, tree bark, peat, etc. Sometimes, undecomposed elements like branches and bark remain. I have used compost as the sole substrate as well as mixed with other substances. A successful mix that I used to use is: 50% silica sand and 50% sifted compost.

Natural peat; natural peat is a precursor to charcoal formed as a result of the acid and anoxic decomposition of the vegetable matter. Depending on the origin, the peat can be called blonde peat if it is formed from sphagnum moss or black peat if it is formed from other plant matter. In both cases, this peat is formed naturally in areas that are waterlogged. As plants die, their remains form a growing accumulation of oxygen-poor layers that turn into peat. Blonde peat has a low pH of about 4, and contribute few nutrients. Black peat has a higher mineral content and a higher pH of around 5-6. Black peat should be mixed with other elements like vermiculite and perlite that help allow air circulation through the substrate.

Beech leaf litter (Fagus sylvatica); This is a substrate that is very highly recommended by Jan Bastmeijer in his web site (the Crypt Page) and Nielsen in his article "Cultivation of some difficult Cryptocoryne species in humus-rich leaf-mould" in the German magazine Aqua-Planta, nº 17, 1992. According to the author, the substrate formed by accumulated layers of the leaves is rich in humic acid. Nielsen also mentions the importance of humic acid in the growth of difficult cryptocorynes like those found in peat swamp forests. According to Nielsen, this substrate results in a more vigorous and better growth over a long period. The pH of this kind of soil is very low, around 4-5. The substrate can be used alone or mixed with other mineral soils, clays and sand.

Chestnut tree leaf litter (Castanea sativa); This is the Spanish version of beech leaf litter. This substrate is sold in gardening centres for acid-loving plants. It has the same characteristics as beech leaf litter. In many cases it is mixed with heath soil and blonde soil (both acidic soils). It has a pH value of 5.5 - 6.5. At the moment I have obtained good results with this soil. I also mix it with coconut fibres. We can obtain the substrate in the wonderful chestnut tree forests that cover Spain.

Coconut fibre; this is a very new soil for me. I have only used it for some month with success as a result of a friend's recommendation. It is a very inert substrate made of basically lignine from coconut husks and fibres. It offers a very good characteristic for growing cryptocorynes, namely its good water retention ability, and at the same time it allows for good drainage. The fibre has a pH value of 5.5-6.5. In the time I have been using it, I have watched the plants develop a very healthy white root colour. But I think that more time is needed to test this subtrate on more sensitive species.

Akadama; This is a clayish soil from a Japanese region called akadama. It is extracted by removing the superficial top layer. We can find it in bonsai gardening centres, usually as solid granules. It has a slightly acidic pH, and the plant roots grow perfectly within the substrate, thanks to its high porosity. There is a variant of akadama named kanuna, which is more acidic. Kanuma is extracted in the same places as akadama, but from deeper layers. This soil is good for difficult rooting plants, and is a very good choice when mixed with leaf litter or coconut fibre.

Sepiolite and others clays; Sepiolite is a clayish mineral used industrially as an absorbent. Mainly it is sold like kitty litter. It has a marvellous ionic exchange capacity and a good retention of water. It is sold as granules and has a good resistance to grain disintegration. But its pH is high (7.5-8.5) enough, and for this reason can only used with easy-to-grow cryptocoryne (such as those from Sri-Lanka) and of course mixed with other elements. Others clays that we can use are the ones used in kids school hand-works. This clay has a pH value around 7. We can use clayish soil collected near our home, but we need to be sure that it is free of pesticides and other contaminants. We also have do a simple test with hydrochloric acid to see if the soil contains any calcareous elements.

Vermiculite; This is a laminar mineral similar to mica. It is expanded by heating the material up to around 900º C. In this process, the water in the sheets causes it to break in thousands of little layers. This structure retains a lot of water and provides a good ionic exchange capacity. It is totally inert and contributes only the element magnesium. Its pH is neutral, and this clay is wonderful for difficult rooting plants. It can be used as the sole subtrate or as part of a mix. If we use it as the sole substrate, nutrients should be added hydroponically.

Moss; recently it has been found that sensitive plants can be grown in a substrate based on non-decomposed sphagnum moss. This method s very widely practiced in Japan and contributes to successful results. The value of pH is quite low, and the substrate has a very good air flow and the roots grow very well within it. I personally use live moss (Vesicularia dubyana) to get the rooting of rhizomes of different species (C. aponogetifolia, C. wendtii, C. walkerii, C. becketii, C. pontederiifolia, C. spiralis, C. balansae, C. x willissi, etc) with success. Now I am testing the live moss culture as a long term subtrate. In stores that sell supplies for reptiles, you can find a great variety of mosses that we can use for our culture.

Others substrates; there exists plenty of material that we can use for our purposes. I will only mention a few: beech wood chips, rock wood, pine bark, perlite, arlite, humus-rich forest cover, etc.

Water

We have mentioned earlier about the importance of the atmospheric humidity, but here I must speak about the importance of the soil humidity.

Cryptocorynes grow with their roots submerged in a flooded soil, for this reason the water in the soil plays a great importance. We can grow emerged cryptocorynes without soil in the water but this requires a very high air humidity. A better way to keep a high level of environment humidity is to have water on the bottom and covering part of the pots. Apart of the resulting evaporation, this water is the medium that contains the nutrients. The water should be soft and acid; however, there are some species which can grow with hard water. But if we use a soft and acidic water the range of species we could keep will be greater. We can use reverse osmosis systems to make suitable water for our needs. Another good practice to get a low pH is adding dry leaves on the bottom, where the humic acids will do the rest.

We can keep the water still, but the best results are obtained with a gentle water flow between the pots. We can get this soft flow with a small water-pump or powerhead.

We must pay attention to the water temperature too, as this affects the air temperature. In the most cases, a water temperature of around 25ºC is fine. Classical aquarium heaters and heating threads can help us get a optimal temperature. In winter we must be careful with the insulation of the setup, if it is placed outdoors. In countries with a mild winter an outdoor setup to grow cryptocorynes is not a problem.

Nutrients and fertilizations.

As I have previously explained, water is the medium in which the plant gets its nutrients. If we are using non-nutrient rich soils, we will need to add nutrients to it. We must add nitrogen, phosphate, potassium, and micronutrients, in particular iron. I have used a regular plant fertilizer for indoor plants, but adding just half of the recommended dose. I add fertilisers once a week, and change part of the water every 2 weeks. I spray fertilizers at half of the recommended dose, once every each 2 weeks too. Iron is added once a week, using chelated iron (EDHHA).

Setting up to growing emerged cryptocorynes.

It´s easy to make a little set up to grow cryptocorynes. First, we only need a hermetic container. We will need to adapt a glass cover that will allow suitable light entry in outdoor setups or put up an artificial lighting system using fluorescent bulbs.

If we use an old fish tank, we will only have put a few centimetres of water at the bottom, set up a little water-pump and a water-heater. We will then place the pots into the tank and cover the tank with a glass sheet and set up the lighting.

An outdoor setup is more difficult, as we must maintain a temperature above 20ºC. To keep this temperature stable, we can use a foam box like those used to carry live fish. A very cheap way to cover it is to use a transparent plastic film. This is a good choice for the summer season, but in winter heating is needed.

We can use a heating cable under a gravel layer, and the gravel will retain most of the heat.

If we have enough room, setting up a little hot-house would be the best option. A good insulation design will be important to save electricity.

Placing the hot-house is quite important, as it needs sufficient light but never direct sunshine, at least in the summer, as the temperature could reach 40ºC, and kill the plants.

Potting a cryptocoryne.

Finally, I will provide some easy guidelines on how to pot a cryptocoryne, and avoid damage to the plant.

In this example, I repot a C. pontederiifolia that was growing in a poor quality soil. It was growing for around 8 month without showing good growth. The soil was a mix of clay, sand and compost, and I decided to change to another substrate. In this case, I chose a pure coconut fibre substrate.

The first step is to remove the old soil, and clear the roots with water.

After that, cut the longest roots and fill half the pot with the new soil. Put the plant on the soil and fill the rest of the pot with the new subtrate. Pushing the soil gently with a wooden stick to refill the gaps between the roots is a good practice.

Finally, label the plant to monitor its growth. I type the latin name, starting date of the pot, its origin and a control number.

- The Crypt Page. Jan D. Bastmeijer.

- "Cultivation of some difficult Cryptocoryne species in humus-rich leaf-mould". Niels Jacobsen; Aqua-Planta nº 17, 1992.

- Aquarium Plants. Christel Kasselmann.