In this post, we review the most popular orchid potting media used by orchid growers and provide recommendations on which one is more ideal than the other.
Bark, moss, clay are potential options as well as as coconut husk, glass beads or water
To read more about general properties of potting media, click here or read on to review the most popular options.
I. Bark
Benefits of using bark:
bark potting media have 1-1,5 years lifetime before it gets discarded (assuming re-potting was done properly, the plant is healthy and it has ideal growing conditions),
suitable for different sizes of orchids as bark is available in different sizes so orchids with thin roots should get smaller bark as opposed to orchids with thick roots,
in an ideal world, using bark potting media is considered a “low maintenance” approach
Disadvantages of using bark
without sufficient ventilation bark promotes spread of bad bacteria that not only smell bad but root rot can destroy the entire root system and the plant;
bark accumulates fertilizer that can burn roots over time
this potting media does not let the whole length of orchid roots to be exposed to light so the plant cannot perform photosynthesis via surface of all its roots
after about 12-18 months the pH level of bark becomes too acidic that hinders the development of the plant so re-potting is needed then and old bark cannot be re-used
Bark is a great choice for growing orchids as long as humidity and ventilation are kept at optimal levels and proper re-potting is done when needed.
Overall rating: 4 out of 5 points
More details about bark: Bark is probably the most widely used orchid media. Epiphyte orchids, such as phalaenopsis plants grow on threes so as potting media, bark comes as a natural choice. It is not very water retentive and dries out in a few days time based on the temperature. The drying process of bark provides orchids with humid air inside the pot. While humidity is important for orchids, not having sufficient ventilation of this humid air means it is a breeding ground for all sorts of bacteria which often times causes root rot and can destroy the whole root system. Because bark dries out relatively quickly, it is crucial to let bark dry out properly and only water the plant when its roots become silvery white colored. Letting bark dry out helps preventing root rot.
Bark decomposes slowly over 12-18 months based on the amount of water it is exposed to. Until such time, the air is trapped among the bark chips which provides the orchid with some humidity and ventilation as long as enough holes are present on the pot. Bark is available in different sizes so that suits different types of orchids. Odontoglossum, for example, would require smaller bark chips as opposed to bigger bark chips that a mature phalaenopsis plant would need. When looking at the size of the bark chips, phalaenopsis (and other epiphyte orchids) need some air around the roots so should not be all covered with coffee ground-like soil.
Bark can accumulate some of the fertilizers over time so about once a month it is recommended to rinse the orchid well with pure water - rain water, osmosis or distilled water - to flush out access mineral that might have accumulated in the pot. The pH level of bark starts to become more and more acidic as bark starts to decompose so re-potting is advised to happen every 12-18 months.II. Sphagnum moss, coconut husk or mixing them with bark
Benefits of using either sphagnum moss or coconut husk
increases humidity within the pot as it retains much water and dries out very slowly compared to bark; therefore, it is ideal to mix with bark if your orchid is watered properly but dries out quickly and it shows signs of dehydration;
ideal for mass producing orchids. sphagnum moss and coconut husk are preferred choice of orchid nurseries and garden centers to nurture young orchids (though their growing conditions are different than a typical home environment).
Disadvantages of using either moss or coconut husk
increases probability of root rot, growth of fungi and bad bacteria
if mixing with bark, it can be challenging to find the right amount of moss or coconut husk to use in each pot. The ratio of bark and moss or coconut husk should be relative to a) the humidity of your home and the amount and b) distribution of ventilation holes of the pot and c) type and size of orchid
Using sphagnum moss and / or coconut husk mixed with bark helps to get a more water retentive potting mix, however, ideal ratio & place of moss and bark pieces can be difficult to set-up inside the pot. Overall rating: 3 out of 5
Using sphagnum moss or coconut husk alone as potting media without bark is not recommended unless you have a separate room for orchids (e.g. glasshouse) so can create tropical climate conditions. Overall rating: 2 out of 5
More details about moss: Moss, especially spanghnum moss became a very popular orchid growing media. It is praised as one of the most water retentive, natural potting media available for orchid growers. Indeed, spanghnum moss can be used for many orchids, though at different stages of their life. The ideal use-case for spanghnum moss is hugely dependent on other things like humidity, ventilation and watering. The type of the orchid is probably the most important factor that will determine when and how much of moss is going to be used if it should be used at all. Cattleya and odontoglossum orchids can tolerate more water than phalaenopsis so a moss and bark mix can be used for these types of plants at various humidity levels. Alternatively, moss can be used only on the surface of the potting media to retain some humidity inside the pot. This can work if ventilation around the roots is boosted with ventilation holes on the side of the plastic pot to avoid root rot.
Phalaenopsis baby plants are often grown in moss while they are exposed to high humidity and low amount of water. Humidity in a typical home environment will probably never reach that high of humidity levels as baby phalaenopsis plants are exposed to. Spanghnum moss is highly water retentive so exposing it to humid air versus watering it is not the same. Moss soaks up humidity from the air like a sponge so does not need that much of water if the right amount of humidity is provided. This is why, when you re-pot a newly bought orchid, often it has a small sponge-like center in the middle. It is the core of the old spanghnum moss or similar sponge-like substance that may be good for the orchid if other conditions like highly ventilated, very humid environment is provided, however, a typical home is not set-up this way; therefore after you bring the orchid home, this sponge-like potting media over time suffocates the plant unless you remove it or re-create tropical climate conditions. Such rain-forest climate, however, is prone to growth of mold and funghi (above 55% humidity) so it would be advised to have a separate room or even a glasshouse in your garden dedicated for growing orchids. Otherwise, if you keep your orchids in your home, I would advise against using only moss and / or coconut husk as potting media. Mixing moss with bark, however, can have some notable benefits.
It is common to see combinations such as bark and spanghnum moss mixed together and sold as potting mix. This can be beneficial because moss retain water while bark dries out quickly. The problem with this type of potting media is the distribution of moss, bark and ventilation holes. Imagine a root that is exposed to wet moss, it is like a wet sponge so it keeps the root hydrated. Another part of the root, it’s end is exposed to a ventilation hole and bark. The end of the root may dry out and die completely while the other part is being kept in almost constant wet condition in which bacteria then can cause root rot. Chances are that some roots might have an ideal place in such a randomly distributed pot, however, the ratio of moss versus bark and watering schedule relative to the humidity of the room needs to be monitored and adjusted according to the needs of the plant. Moss can be sterilized by boiling it in water.
If you can measure humidity in your home and it is less than 50% or you cannot measure humidity or cannot increase it and your orchids start show signs of dehydration (floppy leaves, wrinkles on leaves and /or roots) then try and experiment with re-potting and adding extra ventilation holes and a little amount of moss or coconut husk to your potting media and monitor the plant closely and see if the plant start to show signs of recovery in a few week's time. Otherwise, if the plant still dries out too quickly consider either increase the humidity or amount of moss used. Find out more about watering schedule and signs of healthy phalaenopsis here.
Coconut husk is similar to spanghnum moss in terms of water retention and they are often used interchangeably.II. Clay pebbles and clay pots
Benefits of using clay products
low water retention is less likely to cause root rot so clay may be used in humid environment at lower temperatures
clay decomposes very slowly compared to bark so clay pebbles can be re-used during re-potting process (boil in water to sterilize clay pebbles before re-using them)
Disadvantages of using clay products
relatively time-consuming to properly monitor and control the chemical, pH level of clay without harming the plant
low water retention means in warmer months very frequent watering is required
even with proper watering the orchid may suffer from dehydration if humidity of your home is too low (below 50%)
if pH level of clay becomes too high, the plant cannot absorb minerals from fertilizer so it cannot grow new structures (flowers & flower spikes, leaves, roots, keiki)
roots in clay pots cannot absorb light (photosynthesize) because clay pots are not transparent
clay pots are not see-through as opposed to plastic pots so roots are not visible and it is difficult to check for root rot and other potential diseases just by looking at the plant that is grown in clay pot
Time-consuming to monitor its chemical (pH) state and control humidity therefore clay products may be suitable for those either looking for a challenge or have no other alternative. Overall rating: 2 out of 5 points
More details about clay pebbles and pots:
Clay pebbles are usually available to buy in garden centers. Clay products such as clay pebbles and clay pots are created from clay that was heated at very high temperatures. Clay products therefore inorganic as they are man-made. Without exposing clay to high temperatures, it would not be durable enough to use. For orchid care, buy products that are sold as clay pot or clay pebbles and avoid buying clay in its pure form because that would be too wet to use for orchid care.
Clay may require relatively high maintenance not only because of its low water retention property but also because of rapidly changing pH level. The pH level can be somewhat lowered by boiling clay pebbles in water though orchids do not like frequent re-potting. A very acidic potting media (with high pH) stops orchids from absorbing nutrients from fertilizer and can therefore seriously damage the plant over time. pH can be monitored with store bought test strips for example that are often found in pharmacies. Frequent monitoring of pH is strongly advised when using clay as potting media for orchids. In this case, keep in mind that different types of orchids may need different pH levels to thrive and control the clay’s pH accordingly for different types of orchids if you have more than one species in your collection.
I have seen people using clay pebbles and put rootless orchids on top and pour water just below the surface of clay pebbles. This way, they claim rootless orchids can be revitalized and as a result; and plants start grow new roots. On the longer term I would caution against such practice because the part of the orchid that touches the clay is likely to start becoming more and more acidic as days go by and that acidic state will slowly spread to other parts of the plant so the pH of pot increases. Orchids cannot grow if pH is too high. To avoid this scenario, other inorganic media such as glass beads or decorative rocks with glazed surface may be used instead of clay.
Clay products are usually unglazed which means they are somewhat water-retentive and so their pH changes over time. Glazed clay, however, is usually dishwasher safe and does not absorb water so its pH is not likely to be influenced by clay material that is under the glazed surface. If that glazed surface get damaged, it is again prone to pH changes; therefore - for beginner orchid growers - I would not recommend the use of glazed clay either.V. Growing orchids with inorganic or without potting media
Man-made, inorganic potting media are glass beads, glazed stones, and water beads (water pearl, becomes jelly if wet) just to name a few. Some of these are not water-retentive at all while others are very much so. In case of using a potting media that is not water retentive, this technique is called hydroponic or semi-hydroponic (also referred to as full or semi water culture). In most cases, these inorganic potting media are used for decoration and they can serve as a drainage layer so the roots of the orchid are not in constant water. Having some rocks and water below the roots of the orchid also provides extra humidity to the plant.
Orchids do not need potting media to grow if the environment has favorable conditions for them to thrive. At orchid exhibitions, you can find many plants mounted to wooden plates or tree trunks without any traditional pot or potting media present. Other orchids may have some parts of their roots sitting in water.
Growing orchids without organic potting media can be both challenging and rewarding as well. Our next article about full or semi water-culture (“hydroponic“) will describe these fascinating methods. In the meantime, some key thoughts on inorganic potting media:
Water balls may be toxic or not environment-friendly. Controlling the ventilation can be very difficult with these. Usually if they dry out that is the end of their use so need to keep them wet at all times. Overall rating: 1 out of 5
Growing orchids without organic potting media can be time-consuming at the beginning, however, on the longer term this technique beautifies your plants and keeps them healthy at the same time. Overall rating: 5 out of 5
If you would like to read more about potting media, or would like to use a type potting media that is not listed above then check out our article that describes the key properties of potting media in general.
