For the first year or so of growing orchids at home, I just used whatever bag was labelled as “orchid mix” at my local garden centre and assumed this was the best, logical choice; however, on some of my orchids, the roots would turn mushy every 6 to 8 months.
I did look into it, and it became evident it wasn’t the watering schedule, but rather the actual potting medium itself. So I did my research into what the orchid roots actually need in terms of structure (for drainage and airflow) and tested a few mixes myself, and the pattern became obvious. Here is the succinct version of everything I have learned about choosing, mixing and preparing potting mediums for your orchids.
Why the Medium Matters More Than People Think
Most of the orchid varieties that we grow in our homes (such as Phalaenopsis, Dendrobium, Oncidium) do not naturally grow in soil, but rather they are epiphytes or lithophytes, which means that they actually grow on trees or even rocks rather than in soil like a monstera.
Their roots are coated in velamen, which is a spongy, multi-layered outer tissue which is very effective at soaking up moisture from rainfall or even just humid air; however, they dry quickly due to the airflow, as they are wrapped around tree branches rather than in soil. It’s the last part (the drying out part) that I did fully appreciate for years before researching it.
It is here where I have found that a lot of commercially made orchid potting mixes get it wrong. Lots that I see are loaded up with peat moss, composted wood filler and even sand. The problem is that the finer parts of the ingredients fall downwards and settle into an oxygen-poor layer at the bottom of the pot within months. This layer of medium deprives the roots of oxygen, not due to watering too frequently but due to the fact that the medium itself doesn’t let enough air in.
From experience, I have also learned that there is a surprising difference between how long different types of bark last. Raw fir bark is the most common type that breaks down into almost a compost-like structure in 12 to 18 months, whereas aged treated bark (specifically New Zealand Pinus radiata, sold as Orchiata) can hold its structure for as much as 3 to 5 years (this is key to avoiding root rot).
Breaking Down My Go-To Materials
When I stopped buying the pre-made bags of orchid medium and started making my own from individual components, it got a lot easier to troubleshoot problems with my orchids.
Aged Pinus radiata bark (e.g. Orchiata). Good water retention, whilst creating large air pockets due to the size of the bark, and it lasts a good 3 to 5 years before you have to repot your orchid. I find this is the best universal base for epiphytic orchids like Phalaenopsis (which is by far the most common houseplant orchid) and Cattleya, which is also popular. It can, however, turn hydrophobic when completely dried, which is why I like to bottom water my orchids.
New Zealand sphagnum moss (AAA grade). This is my least favourite as it has very high water retention and only lasts for 12 to 18 months before composting and causing root rot. It is, however, good for growing orchids in really dry, non humid environments as the moss releases water through evaporation, keeping the air around the roots humid.
Horticultural charcoal: This has non water retention, so its benefit is to absorb mineral salts and excess fertiliser residue. You do not have to worry about it decomposing. I personally use it as a 10 to 20% additive in my potting mix to prevent problems with fertiliser, as orchids can be sensitive to excess salts from fertiliser.
Coarse perlite or pumice (#3 or #4 grade). This has very lot water retention and also prevents the bark from being compressed, which is great for the roots. It, of course, doesn’t decompose. I use 10% of the pot’s volume to create additional drainage and aeration, which is great if you are prone to overwatering houseplants.
I have several orchids, so I keep bags of most of these on hand as the right combination depends on how you water and where you live (due to humidity and temperature). Here are the potting recipes I personally use…
My Go-To Recipes, Based on How I Actually Water
In my experience, I have found that one medium does not fit every grower, as watering habits and the humidity influence the mix I use.
If you’re a chronic over-waterer (we’ve all been guilty of this) or live in a very humid climate.
I use…
- 80% medium/coarse Orchiata bark
- 10% coarse pumice or grit
- 10% horticultural charcoal
I love this mix as it drains very efficiently and it’s almost impossible to overwater your orchid with this, which prevents the biggest problem for orchid growers.
For a dry apartment (when I used to live in Southern California) or if you tend to forget to water often:
- 70% medium Orchiata bark
- 20% fluffed New Zealand sphagnum moss, loosely distributed rather than packed
- 10% horticultural charcoal
This moss here actually works well as it holds moisture close to the roots, but it doesn’t turn into a soggy pocket that causes root rot as long as it’s not compressed, which it shouldn’t be due to the other ingredients that do a great job of keeping it airy and healthy.
For an orchid that was rootless that I tried to rescue (I got it cheap from a garden centre locally)
- 100% lightly packed, damp sphagnum moss, in a clear slotted plastic pot, with gentle bottom heat underneath.
How I Actually Prepare Medium Before Repotting
This is the part taht I find most guides do not include, but it’s made a massive difference.
- I sift out fine particles from the dry bark (sawdust and the like) by using a colander, as those fine particles can get stuck at the bottom of the pot and turn into sludge, which is not good for orchid roots.
- I soak my fresh bark for 12 hours in warm water before repotting, as dry bark can be hydrophobic, so the warm soak allows it to retain water better. I soak fresh bark for 12ā24 hours in hot water before repotting. Dry bark is naturally waxy and hydrophobic; if you don’t do this,, sometimes water trickles off the surface oof the bark and out the bottom of the pot without absorbing properly. A good soak lets the internal vascular structure of the bark actually start absorbing moisture properly to create the right environment for the orchid’s roots.
- I also fluff up and distribute the moss rather than packing it in. You want a good, even distribution rather than a pocket of moss causing localised damp areas in the soil.
What I’d Tell a Beginner
Whilst creating your own potting mix may cost a little more upfrot it saves you time in the sense that your orchids don’t get root rot and yoy don’t have to replace the potting mix andywhere near as often.
If you have a question, leave a comment below!