Mold on new coco husk?!

[varda.elentari]

I bought some coco husk (sold at a nursery but no brand) to repot my Cymbidium. I pre-soaked it and was surprised to find it absorbed water much faster and became much more soggy than the coco husk I remember using many years ago. It was so soggy in fact that I left it to dry for two days and now when I went to look at it I see the beginning of a bluish-green mold growing on it. Not snow mold I believe, but something that looks similar to this picture, though not as advanced:
https://www.pthorticulture.com/media...767&height=500

Is there any way I could treat the husk to disinfect it or is there nothing to be done? I don't exactly have cash to burn at the moment so having to toss a bag of new media is very frustrating.

Out of interest, is coco husk treated during processing to prevent mold growth? Also, if anyone has recommendations for a better coco husk product, I'd appreciate it.

[Roberta]

First, I feel your pain, having acquired a bag (BIG bag) of small bark (also for Cyms) and when I opened it, found massive amounts of white mold... I have given up on coco husk for Cyms... it was the go-to medium a bunch of years ago. It would still be in decent shape after 4-5 years. More recently, I have found that what is being sold lasts maybe 2 years before decomposing. I'm back to bark (which is usually not moldy...I now get it from a different store)

To rescue the stuff that you have... mold doesn't like dry heat. So you could dry some (enough for your potting job) in the oven - I think a temperature of around 120-125 deg C (250-260 deg F) should be sufficient. (Might stink up the house a bit...if you have a spouse, hopefully an understanding one)

[varda.elentari]

Thanks for responding Roberta! I assumed I happened to buy an inferior product so that's interesting that you noticed a general decline in quality over the years as well.

Thanks for your suggestion. I'll give that a try. I tend to underwater so I'm worried a bark mix would be too dry for a Cymbidium.

[Roberta]

If that new coconut husk is absorbing more water than past batches (and will be likely to stay too wet) - maybe mix some of it in with small bark. You'll improve the moisture retention of the bark, but still prevent the mix from turning to mud too quickly.

[varda.elentari]

That's a great idea! Thank you. I wouldn't have thought of that.

What would you consider as too wet for Cymbidiums? I've never been able to keep them alive before but they're my favourite orchids so I'd really like to learn. I know I don't water enough because I have a huge fear of overwatering. How do you tell when it's time to water in your bark mix?

[Roberta]

My Cyms are pretty much always on the damp side (or even rather wet). As long as the mix drains freely and has air space, it's pretty hard to overwater them. Root rot only becomes a problem once the mix breaks down and becomes more like mud - and airless. Their growth "preference" is pretty much terrestrial. Where epiphytic orchids generally need some drying between waterings, terrestrials don't.

[varda.elentari]

Sounds like this husk will definitely get too compacted then without some bark. If I pot in pure bark, can I even get away with having a teeny bit of water standing in the saucer to make sure they don't dry out while I agonize over whether it's not too early to water again?

I came across some info on beneficial Trichoderma fungi which kills other harmful fungi. Going to see if I can get my hands on some to treat the husk.

[Roberta]

Rather than the saucer, maybe just feel the mix... if it's even a little dry, no harm in watering again. With Cyms, when in doubt, water. I grow my Cyms outside, which is of course different than your situation. But mine get a bath (from sprinklers) every day in summer, every other day in winter unless there is significant rain (maybe 3 or 4 times a year if I"m lucky...) So they never dry out.

[varda.elentari]

I need to stop being afraid to water well then. Thank you!