Green Culture Singapore Articles

Contributor & Photos: orchideenjaeger Available online 1 May 2005

Dendrobium carronii


Dendrobium carronii was considered one of the most difficult plants to cultivate from flask to maturity. My mentor would always tell me, "Wet is too wet and dry is too dry." This plant prefers the dry side but seedlings need a certain amount of water to prevent drying out. Most of the antelope Dendrobium growers would caution one to keep it on the dry side but more often than not, it tends to be too dry and seedlings would end up desiccated.

This method as perfected through trial and error and I'm most grateful to the people who made flasks available for sale in order for me to try out various methods.

When selecting "flasks", besides looking out for the features of well-cultured "flasks", bear in mind that the maturity of D. carronii is determined by the size and thickness of the pseudobulbs not the leaves. Seeing a lot of leaves does not necessarily mean the flask is matured but it can mean that the flask has not been replated for a sufficient number of times.


Seedlings should be well spaced apart.

No odd surface growth, such a molds and bacteria, which are characterized by fuzzy growth or odd spots of cream, white or green.

Little browning and no bleached plant parts. A few brown leaves are acceptable especially if the plant is deciduous. If blackening or browning of seedlings occur en masse, it could mean that there's contamination within the core - which is not visible until unflasking is done.

If one decides to buy a flask immediately, buy one with matured seedlings but not those which are too thin and weak looking in a crowded flask.

Left: View of plants inside the flask.
Right: View of plants from outside the flask.

The old pseudobulbs of D. carronii usually sheds its leaves after the new pseudobulbs are formed, for that reason, it is alright to have browning leaves within the flask as it is part of the growing process. Note also that the seedlings are spaced apart and there is room for more growing to take place - but as to when to unflask is up to the grower's opinion, but I would not keep matured flasks for more than 6 months. Also note that there are no signs of contaminants within the flask. If one is keeping the flasks for some time before finding time to unflask, do check once every few days for signs of contamination setting in. Sometimes the growth of contaminants can overwhelm the seedlings.


Stick for breaking up agar and to ease the removal of seedlings. It can be a piece of straight wire, glass rod or even chopsticks. Just make sure is clean - soak it in disinfectant or heat it (if it's heat proof)

Scissors for trimming off the brown leaves, separating seedlings or roots. Try not to tug the seedlings but instead gently snip them. Tugging them may cause unnecessary tears.

Lighter for flaming and sterilizing. When flaming cutting surfaces, do flame until the metal surfaces start glowing - not run the flame with one swift motion and that's it.

A small plastic basket for draining the seedlings. It is not wise too keep the seedlings too wet when working with them especially if there was no fungicide or bactericide used on them.

Do have a small plastic tub or bowl to rinse the seedlings.

A plastic basket tray to place all the tied seedlings in the end.

Tying materials are essential in for this modified method. There are various tying materials that can be used ranging from (left to right) hard telephone wires, fine cotton parcel string or straw strings.

Hard telephone wires are very similar to twist ties but they are smooth rounded wires without the sharp edges. To use, just separate them out and cut into appropriate lengths, twist wires to tie.

Cotton threads are biodegradable and after some time, they will just decay and can be removed easily for aesthetic purposes. They are also water absorbent.

Straw strings are common in Asia and they are used mainly to string plastic bags to hold food or drinks. It is my personal choice of tying material (must have rubbed off from my mentor). It is durable and long lasting - especially useful for plants that take a long time to root. The only flaw is that they need to be pre-stretch or else they will loosen after some time. For this method, I use straw strings cut into 30 cm lengths and they are stretched after cutting.

Sphagnum moss is chosen as the wetting material for tying seedlings with. To prepare sphagnum moss correctly, mix just enough water to wet the dried moss. If you add too much water and drain the excess, you are in fact removing the substances that give sphagnum moss its antiseptic properties.

Do not attempt to tie dried sphagnum moss before watering - dried sphagnum moss expands a lot upon wetting and it may just crush the seedling or push it out.

Substrates for tying seedlings come in all forms ranging from artificial to natural. These materials do not break down easily.

One can use natural cork cut into appropriate sizes using a saw. Cork is free draining and it does not absorb water easily. It is rather versatile and easy to shape with a cutting tool.

Styrofoam is an example of an artificial mount. Surprisingly, plants grow on it pretty well if slabbed on with sphagnum moss. One can use it straight or use it double-dipped in quick drying cement. Not all Styrofoam are made equal and some may contain some substances toxic to plants. Some may also have some oils that may coat the plants and harm them. When cutting them with a pen knife, do wipe the pen knife free of oil (well, the pen knife would rust, so use a normal non-serrated kitchen knife).

Fernroot (Xaxim or tree fern) is another example of a natural mount. It is a highly nutritious substrate to grow orchids on and it also absorb water very easily. A draw back for the usage of this material is that it is very brittle and it breaks apart easily. It is usually available in the form of a processed compressed slab. It can be cut very easily with a saw but I have heard of people hacking it apart with a kitchen cleaver.

For this demonstration, I will be using fernroot slab cut into 2" x 3" pieces. When sawing slabs, there will be fibres being sawn out. Do not waste these fibres as they are very nutritious to orchids. Combine these with a potting mix for other orchids - terrestrial or epiphytic.

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