You are not alone; many of us have thought about reusing sphagnum moss for repotting orchids or propagating plant cuttings. This is because buying new ones can be quite expensive. What’s more, we have also heard of some people having success reusing them.
So, can you reuse sphagnum moss? The short answer is:
It’s not recommended to reuse moss and bark to prevent root rot. If you really want to reuse them, you should use high-quality sphagnum moss, which is more resistant to breaking. And you can only reuse the ones that are clean and not decomposed. They should also be disinfected before use to prevent molding and fungal disease.
1. When can I reuse moss & bark?
You can only reuse sphagnum moss when:
- The moss is fluffy and has not been broken down or decomposed into pieces or peat moss
- The moss is clean and has not turned slimy with the appearance of mold and/or green algae
- The moss has not previously been in contact with plants that had a fungal or bacterial infection.
- Check the pH of the water used to soak the media using pH testing strips. It should not be too low. The optimal range for growing many plants is between 5.6 and 6.5. A decomposed media can be very acidic which would lead to root rot.
2. Sphagnum moss from New Zealand vs Chile vs China
How long dried sphagnum moss lasts or how many times you can reuse them depends on the quality of moss you start off with.
Moss from different geographical locations differs greatly in size, the strength of the strands, leaf structure, fragility, and contamination, etc., all of which affect their longevity as a potting medium.
There are approximately 150 species of sphagnum moss discovered worldwide. The most common ones that are commercially available are originated from New Zealand, Chile, China (and also the USA, Canada, and Japan).
Here is a table comparing the quality of sphagnum moss from different locations.
|New Zealand |
|Chilean Moss||Chinese Moss /|
|Strands||Large, robust leaf and long stem||Very leafy with short strands||Small leaf and short strands|
|PH level||4.8||4.8||High PH|
|Salt Accumulation||Hold onto nutrients but will not accumulate salt||Potential to accumulate salt when nutrients applied||Easily accumulate salts|
|Longevity in pot||2-5 years||2-3 years||6-12 months|
The best sphagnum moss is grown natively in New Zealand (Sphagnum cristatum) because of its large, robust leaf structure and long stems for wrapping around the roots of orchids. Depending on the quality of the irrigation water and the frequency of watering and fertilization, this high-quality moss can last for 2 to 5 years in a pot.
Chilean moss (predominantly Sphagnum magellanicum) has shorter strands and has dense leaves which can prevent air ventilation when compacted in pots.
The least expensive mosses may be found originating from Japan, China, Canada, and Wisconsin. The Chinese moss (typically Sphagnum palustre or Sphagnum cuspidatum) and Japanese moss (typically Sphagnum palustre) have short strands and a weak structure which tends to be more fragile and break down quickly, thus requiring repotting every 6-12 months. If they are not repotted, they would turn into a waterlogged mess which would suffocate the roots of your plant.
According to St. Augustine Orchid Society, the recommendation is to use sphagnum moss from New Zealand than the cheaper alternatives from Chile or China.
Here is the link for buying New Zealand AAA Grade Sphagnum Moss. It is a 150g bale that makes 12 Litres, with 70% strands longer than 4 inches (10cm).
3. How many times can I reuse sphagnum moss?
Some people have reported reusing their moss up to three times without any problem. But, if you notice your plant starts having molding/fungal issues and mushy roots, you should toss the used moss.
4. How do you disinfect sphagnum moss & bark?
Even though you start with some high-quality New Zealand moss, you will still face the possibility of molding each time you reuse it.
To lower the risk of molding and fungal disease, you should disinfect the moss before usage. You can boil them in water for 3 minutes. Or, you can do so in the microwave for a few minutes. Then, place them on a newspaper to dry them for a couple of days before reuse.
5. Is it recommended to reuse moss (for orchids and propagating cuttings)?
So far, we have explained in what situations when you can reuse moss.
But, is it recommended to do so? No.
Because it is a gamble. Even though you disinfect the moss before use, the plant or the cuttings sometimes may turn out fine, but other times they do not.
This is because when you disinfect the growing medium by boiling it, you are destroying the integrity of the moss or the bark, making it more susceptible to break down and decompose. Even though it cannot be seen by the naked eye, there is a higher chance that it would have issues with molding and fungal infection.
More importantly, new sphagnum moss (even the New Zealand kind from Besgrow) has a pH of 5.66 (as shown in this experiment) which falls on the lower end of the 5.6-6.5 range of optimal pH for orchid growth. Old moss would most likely be even more acidic and would cause root rot.
To conclude, you should start off with some high-quality long-fiber sphagnum moss, such as those from New Zealand because they do not break down easily.
You can reuse the moss that is still fluffy, clean, not decomposed and has not been in contact with any moldy plant previously.
You should disinfect the moss by boiling it and drying it well before reuse. But boiling them would also accelerate their decomposition, which would lead to issues of molding and root rot.
If you want to reuse the moss as a propagation or growing medium for cuttings, sick plants, or an expensive plant, you may not want to take the risk of molding and fungal infection. In such cases, the best practice is not to reuse any sphagnum moss and switch to inorganic growing media.