Orchids grow extremely well in organic media such as bark chips, sphagnum moss, charcoal, coconut chips and on wood mounts. This is because it mimics their natural habitat.
Orchids are epiphytes and in their natural habitat, are generally found growing attached to trees, on substrates such as rocks (lithophytes) and in soil (terrestrial). This allows the roots to be exposed to air, from which they absorb moisture.
Unlike plants, which require soil for their growth, orchids require a well-aerated coarse medium that mimics their natural habitat. Fortunately for orchid hobbyists, orchids can be grown in a range of media, both organic and inorganic.
Both organic and inorganic orchid media allow the roots to:
- Absorb adequate moisture, without becoming soggy
- Breathe through the air pockets in the medium
- Find their way through the medium
- Anchor the plant firmly to the medium
While both types of media are used by orchid hobbyists, they have their pros and cons, and so a whole lot of exploration and experimentation make this hobby intriguing and interesting, with culture methods constantly evolving with time.
In this post, we will focus on the organic media generally used by hobbyists for growing orchids. I have also linked my preferred brands on Amazon, so that you can choose the same, if you have a requirement.
At the outset let us understand what exactly an organic medium is. This can be defined as any medium that is obtained from plant sources such as bark chips, coconut coir, sphagnum moss, fern blocks, charcoal, cork mounts etc.
Before I begin discussing about organic media, I would like to spell out the pros and cons of using this type of media so that you get a fair idea of their advantages and drawbacks.
|1||Organic media mimic the natural habitat of orchids, which they quickly adapt to and thrive.||They get eroded and broken down and need to be replaced every two to three years.|
|2||They provide a conducive ecosystem for beneficial microflora such as bacteria and fungi that promote the growth of orchids.||They can harbour pests such as insects and snails, which can be detrimental for orchids.|
|3||Fresh media retain adequate moisture and air, and provide good drainage, which help the healthy growth of orchids.||When the medium starts breaking down, it becomes soggy and acidic, promoting the growth of harmful fungi and bacteria, which in turn leading to rotting of roots and pseudobulbs.|
However, even though an organic medium has a limited lifespan and gets eroded or broken down over time, say 2-3 years or may be even less, depending on the conditions it is subjected to, it remains the popular choice of hobbyists all over the world. This is because they would like to grow orchids as they would in nature.
Second, over the years, potting mixes that eliminate the inherent drawbacks of organic media are ensuring that once again organic media are gaining preference over inorganic media.
Even orchid nurseries and public gardens the world over, use organic media for growing orchids.
Types of organic media
The following types of organic orchid media are preferred by orchid hobbyists:
Pine bark is recommended to provide natural conditions for growing orchids. This also lasts longer and disintegrates more slowly compared to other media like coco chips and sphagnum moss.
Commercially available in various grades to cater for the growth of various types of orchids, it can be classified into fine grade, medium grade and coarse grade, depending on the size of the bark chips.
Fine grade retains more moisture and less air pockets, which is suitable for terrestrial orchid and seedlings. Medium grade bark is most popularly used by orchid hobbyists and caters to the needs of many types of orchids. Coarse grade bark, on the other hand is used for larger plants and those that require a well-draining medium. It provides adequate anchorage, and dries quickly even in a large pot or container.
I grow my orchids mostly in a mixture of bark chips and sphagnum moss. I prefer using premium imported medium sized pine bark that is clean, with smooth edges and provides my orchids the right environment for their growth. Moreover, this medium lasts for 3-5 years, so it works long term and saves me the hassle of repotting frequently.
Coconut Husk Chips
Coconut husk chips are commonly used for growing orchids as they provide the right combination of moisture retention and aeration, and decompose slowly. However, they don’t drain too well like bark does, for which it is commonly mixed with charcoal to provide adequate drainage.
Since this medium grows abundantly in the countries in South-East Asia, it is inexpensive compared to pine bark chips and sphagnum moss, and is widely used for growing orchids in this region.
It is worthwhile to remember that coco chips are made from mature brown coconuts due to their fibrous nature. They are rich in tannins and resin as well as salts such as sodium and potassium, which can cause root burn and decay. Therefore this medium needs to be pre-soaked for three days, changing the water after each day to remove the tannins, resin and salts.
There is however a disadvantage if this medium is used for growing orchids since it has a strong affinity to bind with magnesium and calcium, which are provided as nutrient fertilizers for orchids. This can lead to deficiency diseases in your orchids. To overcome this, the coconut chips can be buffered by soaking them in a solution of calcium nitrate and magnesium sulphate. This treatment will ensure that your orchids can absorb the supplied magnesium and calcium salts optimally and grow well.
Immature husk chips, on the other hand, are not suitable for growing orchids since they are tough and impermeable to water. Moreover, they retain excessive moisture and are prone to mold and algae attack. This can destroy your orchid’s roots, harming the plant majorly.
I use this medium for orchids that need a moisture retentive medium. I soak it repeatedly in fresh water and pre-treat it with calcium nitrate and magnesium sulphate solution. This ensures that it is safe to use.
Sphagnum moss was the preferred medium of growth for phalaenopsis orchids for very long and is still used commercially by orchid growers since it helps provide adequate moisture and air to the orchids.
But a word of caution here, you need to check that it is not compacted, but is loosely packed, so that it provides adequate aeration to the roots. It is also highly absorbent, so you need to control the watering. This ensures that the medium does not become soggy and compacted, thereby choking the roots and leading to their decay.
If the medium starts getting compacted, then it is time to be replaced by fresh sphagnum moss, which is springier to the touch.
Sphagnum moss is commonly used in potting medium along with bark chips to increase moisture retention and increase the duration of the wet-dry cycle. I prepare my potting mixes using the highest quality of pure sphagnum moss as it is free of dirt and other contaminants. The quality is consistently good and it lasts for a long time.
Fern blocks are tightly enmeshed fern stems that are closely packed and provide a good combination of moisture retention and adequate drainage. This is suitable for mounting orchids such as dendrobiums and other species orchids. It lasts for a very long time and decomposes slowly. But it requires daily watering as other bark mounts and so makes the hobby more tedious. Fern blocks are expensive and are sourced from the wild. They are mostly sold in eastern India, where ferns grow in abundance.
However, they grow very slowly, and therefore, sourcing them for growing orchids can adversely affect the ecosystem.
Charcoal provides excellent drainage and is commonly used with coconut husk chips to provide good drainage and prevent the medium from getting soggy. It is recyclable and inexpensive, thereby saving on the recurring cost of changing the medium for growing orchids. It is also suitable as a coarse well-draining component of mixes for your vanda and other bare-root orchids.
Cork and driftwood mounts
Cork bark makes for very good mounts for orchids as it does not absorb moisture and is thick and hard, making it resistant to swelling up and disintegrating when soaked. When the plant outgrows the mount, it can be transferred to another mount and the old one can be reused after boiling and sterilizing it. They look attractive and provide a natural backdrop for your orchids.
Driftwood or dry pices of wood are cleaned up and are used as decorative mounts to give your orchids a natural environment. Orchid plants are harnessed with sphagnum moss and nylon wire to the wood to make attractive displays.
Cork mounts beautifully offset your lush green orchids and make for great displays due to their textured surface. Also, a lot of my locally sourced wood mounts disintegrated after two years, forcing me to consider cork bark as a more long term solution. The price is a little more, but works out well in the long run. The best part is that you can reuse these bark pieces even after years of use. You can buy cork mounts and chips here.
To learn about how to mount your orchids and look after them, you can check out my post, Project#6: Mounting your orchid on cork bark
Popular organic media mixes
A lot of ready-to-use organic potting mixes are commercially available for growing your orchids. Based on the moisture requirement and your local climatic conditions, you can choose one that is most suitable for your orchids.
They offer the convenience of saving on time and effort, and prevent the messiness of pre-soaking your media and mixing it. The mixes are also pre-treated to keep them free of pests and fungus.
Bulk purchases also make ready mixes more affordable. So if you have a small collection and don’t want to spend a lot on potting mixes and have them lying around for a long period, unused, you can get your friends to club their orders along with yours, and the economics of bulk purchases will result in significant savings.
Ready-to-use organic potting mixes can especially be used by people who are new to the hobby of growing orchids. As you gain an understanding of the function of each component of the mixes, you can formulate your own mixes, which you can test on your orchids and optimise them further to produce the best results.
I make my own potting mixes by sourcing the ingredients separately.
Choosing an organic potting mix for your orchids
You need to choose your organic potting mixes with care. The basic requirement is that the medium should be well-draining and provides the right balance of moisture and air to the orchid roots. This will provide a good wet-dry cycle, which is significant for the healthy growth of orchids.
While there is a general thumb rule of the kind of orchid mixes that are suitable for phalaenopsis, cattleya, paphiopedlums, oncidiums, based on their morphology and moisture requirements, you need to also consider the climatic conditions of your locality, the fluctuations in temperature and humidity, and your grow area conditions, the type, size and porosity of pots, before you prepare your potting mix.
The American Orchid Society has put forth the following guidelines for selecting media for different types of orchids:
|Orchid type||Pot type||Wet-dry cycle (Gap between watering)||Potting mix|
|Phalaenopsis, paphiopedlum, miltoniopsis, miltonia, cymbidium and other terrestrial orchids (moisture-loving orchids)||Clay or plastic; Large or medium||Up to 7 days||Medium to fine grade; High moisture retentive; Well-draining|
|Cattleya, oncidium/odontoglossum alliances (sympodials with well-defined pseudobulbs)||Medium to large; Clay or plastic||4-7 days||Coarse to medium grade; Moisture-retentive, yet well-draining|
|Dendrobiums, vandaceous types, terrate, pendent type oncidium types and other genera||Clay pots with holes; Slatted baskets/pots||2-3 days||Coarse grade; Well-draining|
|Tolumnia (Equitant oncidiums)||Small Clay or slatted plastic pot||1 day||Coarse grade; Well-draining|
Apart from this, seedling plants prefer a moisture-retentive medium as they require higher level of moisture compared to mature plants, which can use up stored moisture in the pseudobulbs for their survival. However, seedling plants or mericlones also need a drying period of one week between waterings.
Creating your own potting mix
As you get more experienced, you are better able to gauge the type of medium that is most suitable for your orchids. You can mix and match and come up with the best recipe that will help your orchids grow and bloom well in your grow conditions.
Watch how your orchid responds, and pick a medium that is close to the specifications given by the seller. Gradually, increase or decrease the moisture level of the medium by adding the requisite amount of moss or coconut coir to the medium.
If your orchid gets adequate moisture and does not dry out too fast, nor remains soaking wet for days on end, then your orchid is getting the right wet dry cycle for its optimal growth.
Some of the mixes that have gained popularity are:
- Texas A&M University botanists recommend 80% bark and 20% sphagnum peat for growing phalaenopsis orchids.
- University of Tennessee horticulturists recommend a mix made of 3 parts fir bark, 1 part chopped sphagnum moss and 1 part perlite.
- For a finer grade mix for orchids with fine roots, which is more moisture-retentive, mix fine-grade fir bark or coco husk chips with fine charcoal pieces and perlite in a 4:1:1 proportion, respectively. Instead of coco chips, you can use sphagnum moss or even vermiculite. The perlite and vermiculite need to be pre-soaked for easier handling. While vermiculite is moisture retentive, it however, drains out since it is fine in texture. But orchids do respond well to the addition of perlite for aeration and vermiculite for moisture retention.
- For a medium grade mix, use bark or coco husk chips with medium charcoal and perlite in the ratio of 4:1:1, respectively.
The intent here is to provide the right balance of moisture and air for your orchids so that they thrive in your home conditions. While this may be difficult to gauge if you are new to the hobby, you could discuss it with your seller or connect with other experienced orchid enthusiasts on social media platforms and forums, and ask for their suggestions, by mentioning your climatic conditions.
Conserving your medium by treating it right
Now that you have understood about potting mixes and the characteristics of each component, it is very much necessary to treat your medium right, by not soaking it for prolonged periods or allowing salt to build up in the medium. Prolonged wetness with no drying up in between makes the medium acidic, leading to breakdown of medium. This results in the choking up of roots, decaying and making them susceptible to fungal attack.
Even though you source a high quality mix, always ensure that the medium dries off between watering. This will keep it in good condition over a longer period of time, leading to better economics compared to the recurring cost of repotting your orchids frequently in a mix that has the tendency to break down faster.
You can also check out my post, Project#1: Why, when and how to repot your orchids, which will provide you with a step-by-step guideline to repotting your orchids in a suitable medium.