Substrate and Media

Loosening Media

The following media are classified as 'loosening' as they allow for gaps to form in the mix, allowing water to drain easily, and air to flow through the mix. This is important for epiphytes, lithophytes and other non-terrestrial orchids which often require their roots to cycle between being wet and dry so that water and nutrients can pass into the root system.

Bark

This is the go-to media for most orchids, as it allows good drainage, holds a bit of water for a short time, looks good, and has a good weight to it. It is natural, often renewable, and in good supply. Depending on the condition of the bark, how it is used and what lives within it, bark will often last between 2-4 years before needing to be replaced. It can come from a range of trees, but the most readily available is pine bark. There are really 2 types of bark you'd find, raw and aged.

Raw Bark

This is usually found as a bark mulch and is usable, but only for orchids with thick roots with low fertiliser requirements. Often the size is varied and it can contain woodchips. Because the bark is still breaking down it often contains oils that may inhibit growth, and can 'steal' nitrogen from the roots in order to break down the oils in the bark. If it is the only bark available, it's best to soak it after purchase for a week and then leave it in a mound in a protected place so it can start aging.

Aged Bark

This is raw bark that has been aged between 6-18 months to allow oils to break down. This is a more widely usable, more porous bark that is superior in most ways to raw bark. Specialised orchid barks are superior as they have been rolled and screened so that their size and shape is optimal for orchids, and available in many sizes:

3-6mm for seedlings and miniature orchids, keep in mind that it will retain moisture and limit airflow, best for tubes and tiny pots less than 50mm in width
6-9mm for young orchids, again may retain moisture so best not to use it in pots larger than 125mm width
9-12mm best for most orchids and pot sizes, with adequate sized gaps allow water and air to pass through
12-18mm, best for large orchids and large pots, even better for drainage and long lasting
>18mm, Best for very large pots and orchids with sensitive or thick roots that need a lot of drainage

Coconut Chips

Chopped up coconut husk is somewhat hard to find but is a good medium that is quite absorbent, does not clump easily and allows good drainage. It is usually purchased in compressed blocks and has to be soaked for an hour or two so that it can expand to normal size.

Note that its water holding properties can be unpredictable, when new it's perfect but as it gets older and loosens up it holds water for less time, and when it breaks down it holds onto water for far too long. But it's great if you can keep on top of it.

When buying coconut chips or husk, be sure to find out whether it has been washed, rinsed, or leached. If unsure, sit a considerable amount in a bucket of water and let it soak overnight. Drain the water, rinse 2-3 times and it should be good to go.

Wood Chips

This media is not popular with growers. The main issue is that often the chips are too coarse, and depending on the plant they came from, and very fresh wood may contain oils that inhibit growth. But it is a long lasting media with good water absorption properties and often plants just sink their roots right into the wood.

Perlite

Expanded Clay

Styrofoam

Fine Media

Fine Bark

Coco Peat

Potting Mix

Vermiculite

Connective Media

Spagnum

Rockwool

Mountings

Wood

Tree fern

Cork board

Natural Cork

Trees

Palms

Rocks