How To Use Orchid Composts

If it’s come time for you to re-pot your orchid then you’ll need to know what type of orchid compost or potting media to use. There’s no real mystery to orchid composts and re-potting but it’s helpful to have an understanding of the materials. Once you know what the properties of the materials are you can mix and match to provide the best compost mix for your species of orchid.

First a couple of quick tips about re-potting your orchid:

1) Try to re-pot shortly after blooming has finished.
Re-potting will cause some shock to your orchid and it will take a little time for it to become acclimatised to its new conditions for this reason it’s wise not to re-pot while your orchid is flowering.

2) Soak the compost in water overnight before potting.

3) Clean the pot you intend to use thoroughly before you use it in order to kill any germs or other bugs.

Orchid Composts

Different composts or mediums have different characteristics and you can mix and match them to provide the ideal potting conditions for your type of orchid. For example, your orchid species may not grow pseudobulbs therefore your potting medium may be required to retain moisture for longer. A potting compost containing rock wool will retain moisture well but becomes compacted quickly so you may need to use another media such as perlite to aid drainage and airflow.

Sphagnum Moss
A great material for retaining water and is available living or dried, it can be used on it’s own but is used as part of a mix more often than not.

Peat is formed in bogs over a long period of time from sphagnum moss and will retain even more moisture but should not be used as compost on its own as it’s a very dense material and will restrict drainage and airflow.

Rock wool
Rock wool is also good at retaining moisture but has the disadvantage of becoming very compact quite quickly so you should probably mix this compost material with another longer lasting coarse medium.

Expanded perlite is a material made from processed volcanic glass and is good at retaining moisture and degrades very slowly. It’s usually used as an addition to other orchid composts as it reduces the effects of compacted organic materials helping to maintain good airflow and drainage for your orchids root system.

You should use cork as part of a mix only as it breaks down too quickly to use on its own really. It’s effective while it last but can be fairly acidic.

Can be used to compensate for acidity in your compost from mediums such as cork, mentioned above. Be aware though, that charcoal absorbs minerals, so if the water in you area is high in mineral salts you will want to purify it before you water your orchid.

Fir Bark
Probably the most popular orchid potting media, it compacts relatively slowly reducing the need to re-pot too often. It retains moisture well and comes in different grades. One disadvantage to Fir Bark is that the bacteria responsible for breaking it down consume available nitrogen so you will have to use a high nitrogen fertiliser to replace it.

Coconut husk
Coconut husk is a great compost material ideal for orchids of all varieties. It’s a naturally occurring waste by-product of other processes and it’s sustainable which means there’s no real environmental impact. It retains water, air and nutrients well and is course so it drains well too. As an organic material it will break down over time although relatively slowly giving your orchid time to grow between distruptions.

Expanded Clay
Is a good man made potting material and is non-organic so will not break down over time. Its real disadvantage are its cost and weight which makes it expensive to ship.

Matthew Clarke has been growing orchids now for over seven years and considers it to be one of the most rewarding hobbies there is. When he’s not spending time with his family he enjoys hiking and writing. You can read more about using orchid compost at his website

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