by Jan D. Bastmeijer
These pages are on the cultivation and taxonomy of plants of the genus Cryptocoryne (Araceae)
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How to cultivate

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Submerged in aquaria
Most people cultivate Crypts submerged in aquaria. The technique is quite simple. A layer of (washed) sand of about 5 cm is sufficient. Enrichment with some clay is good. Some people use small balls (1 cm), to put around the plants. Others mix the sand with powdery clay. If you want to spend a lot of money, you can use (commercial) laterite soil. There are records that someone used the small droppings of rabbits instead of the clay balls mentioned. Another way to get enough nutriments in the soil, is to add many fish to the aquarium from which the detriments will do. The kind of water is important. Most Crypts like soft water, but others do not. For example, its hardly impossible to cultivate C. affinis, C. aponogetifolia in soft water. At any rate it is important to replace about one quarter of the water on a weekly basis.
C. aponogetifolia and C. affinis growing in a small aquarium at A.J.Huurman. Moderate temperature (ca 20 °C, no heating). Both species prefer hard water (calcareous). The tank is filled with only a few cm gravel. Fish excrements provides the plant nutriments. This tank stands for years and was to be cleaned some time. Heaters were already removed. The tube in the middle on the surface is not for air bubbles but is part of the inflorescence of C. aponogetifolia. A great surprise.

Temperature around 25 °C, light about 12 hours. The use of CO2 is not necessary. There are many don'ts and a few dos. Most Crypts don't flower when submerged but some do.
There are even records on cultivating Crypts in garden ponds in moderate climates.

For the emerged culture there are many possibilities. Choose one of these techniques to get your plants to flower.
Like the submerged culture, one can lower the water level to a few cm, enabling the plants to get their leaves into the air.
This way is mostly seen in botanical gardens: plants in the basins are just below water level. This 'semi-emerged' culture is quite stable but requests a lot of room.

The author in Oxford Bot.Garden (UK). Most botanical gardens hardly have a collection of Cryptocoryne. As they have one, they are often not well labeled.

An efficient way is to put the plants in pots of ca 5-10 cm and place them in an empty fish tank or specially built container. Moistened peat litter between the pots provides a good climate, the tanks closed with a glass cover. Another way is to circulate water around the pots, especially efficient when cascading a couple of tanks. The culture in pots is practical for taking pictures and prevents runners from walking around.

Copenhagen Niels Jacobsen in the (not public) hothouse of the Botanical Garden of Copenhagen (1985). Plants are potted and stand in a few cm slowly running water. Note the HQL bulbs for additional lighting in winter. The table is covered by a plastic sheet to keep humidity near to a 100%.

A variant on the semi-emerged culture which has proved itself is to use plastic crates, the ones to put in children's toys for example, filled with soil just flooded with water.


At left, C. elliptica is growing in a plastic crate filled with pure beech tree soil (top view). At right the same species potted (10 cm size) in a granite soil mixture under the same conditions (at Copenhagen). This most luxurious growth is also reported for other species, for example C. pallidinervia.

photo Jacobsen

Washed sand mixed with peat litter (50/50% volume) is an excellent medium to cultivate Crypts. Most species will grow in it. For there is any nutriment in it, you can add some clay and/or you have to spray your plants every week with a normal indoor plant fertilizer.
You can use forest soil from the beech tree (Fagus sp.) to replace the peat litter or to mix it with. You can even use pure beech tree soil for species from Borneo which are difficult to grow, mixed , if any, with some clay powder. Be aware that beech tree soil is extremely acid. The pH in your tanks can go below 4, dissolving metals and even some plastics.
Good results are made with meranti chips instead of peat litter. Pure clay proves to be difficult.

Growing Crypts outdoors in a greenhouse is very nice though you will have to shade most Crypts because of the light.
Indoors, the plants can be illuminated with fluorescent tubes. The colour of the light does not matter very much. Two or three fluorescent tubes over your tank for 12 hours daily will make most species flower. Some species will not flower in these conditions because they need more light, e.g. C. crispatula.

The collection of the author around 1985. The tanks are about 60x80 cm, demanding together one square meter floor. The tanks are standing on a box which is heated by bulbs (see below). Later a flow system is build, heated water cascading through the tanks, and the heating boxes were eliminated. Illuminating is done with several types of fluorescent tubes. The most cheap will do as well as the special ones, but you will have to accept the poor colour quality.

The best temperature for cultivating Crypts is around 25 °C. Many species grow well at 20 °C. In an outdoor greenhouse the temperature may cause risks in summer. Temperatures over 40 °C are disastrous for most species, but the common Sri Lanka species (C. wendtii, C. beckettii) will probably survive. A short period on 0 °C is no problem for most species. C. diderici survived one week at minus 10 °C.
A very easy and reliable technique to keep your plants at the right temperature is putting a box under your tank equipped with two bulbs is series. 2 Bulbs of 40 or 60 W in series keeps your tanks about 5 °C above room temperature. Lifetime far over 10 years!

bulbs1 bulbs2 bulbs3
Two identical bulbs in series provide a heat flow in the box under your tank.Call an expert for the wiring.

If you don't use clay or beech tree soil, you will have to use a fertilizer. A common household fertilizer for indoor plants is suitable. Choose the ones appropriate for hydro culture. Spray the leaves every week and put some solution in the pots. Take half of the concentration that is mentioned on the instruction label.

The well known Cryptocoryne disease in aquaria is probably caused by too high a concentration of nitrate. Just change your water regular; every week one quarter as usual in fish keeping.
In emerged culture, many problems may arise. Most problems can be avoided by taking away infected parts and putting the plants not too close to each other. Regularly cleaning up the pots and the surface layer is effective to prevent problems.
Insects can be killed by normal household aerosol sprays. Fungus may be controlled by Baycor from Bayer. Always try first on one or a few plants and wait one week before applying it to the whole collection. Several people lost their whole collection by being too fast.

Micro propagation
Micro propagation is a quick method for propagation. Even hobbyists have a lot of experience with it. Look for special articles on this topic. A point of special interest is to set up a gene bank and, when established, these technique offers a very stable environment.

Already in 1976, Dutch aquarists experimented with tissue cultures.The Agricultural University Wageningen (NL) started to set up a gene bank on Cryptocoryne, but when budgets went down the project was skipped. Commercial growers are not interested in keeping species which are difficult to grow in their laboratories because there is no market for them.

Gibbelerines are plant hormones that can be used to induce flowering. There are a few reports on the use of it for Cryptocoryne, but as far as I know, results of use for Cryptocoryne are very poor.

Entry numbers
Label your plants and give them an entry number to identify your plant and keep record of it. Runners from one plant can hold the same number. Its essential to keep things clear, for example to identify your photographs of your C. wendtii's.

famous labels top down: labels of Möhlmann, Jacobsen and Bogner

Potting your Crypts
All the roots of your dug out Crypts will die and will cause problems in your pots. Shorten the roots to about a few cm, just to give the plant an anchor. Remove the older leaves to just two or three.
Put a piece of filter tissue on the hole in the pot and fill half the pot with your soil mixture. Press it firmly in the pot making a 'hill' for draping the roots around. Place the plant, keep it with one hand and fill the pot. Press on the sides to fasten the plant. Keep 1 cm free height in the pot. Finally, drip some water around the stem.

After a half to one year C. cordata var. siamensis fills the pot. For safety, keep only two plants.

Beginners' luck
When things are going well, you might expect the first inflorescence in about three months. Imported plants may have a hidden bud and may flower at once. It usually takes a considerably longer time. Experiment with soil, light and so on. It is very hard to make some species flower.

Rescuing Crypts
Perhaps the only way to rescue a 'collapsed' crypt is to put the rhizome in an 'old' aquarium. Let the rhizome float on the surface, snails and guppies do the job for you. With good luck, the rhizome will sprout again.

To be updated !

ECS 2017

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