Mold problem with new media after repotting

[ptk]

Hi all. I am a beginner with orchids and originally posted a similar thread in the Potting & Repotting category, but I am hoping to get more traffic here and more help from experienced growers.

Two weeks ago, I purchased Fertilome orchid media, which consists of "Canadian sphagnum peat moss chunks, orchid bark, hardwood charcoal, and lava rock."

I have 3 phals and one of them had already finished blooming and its original media already had mushrooms growing on the bark so it was time to repot (original media was mostly orchid bark). Upon cleaning and inspecting the roots, the roots looked very healthy and plump and stiff. I also sprayed hydrogen peroxide on the roots as a disinfecting precaution read about from other orchid discussions. I repotted the orchid with the new media in a slightly larger clear plastic pot with extra ventilation holes I created on the sides, then watered it since the roots were silvery, dry.

A little over week after that, I had come back from a trip, and noticed through the clear pot that there is white fuzzy mold growth on some part of the roots and those roots turned black/dark gray. My other untouched phals were fine, no mold growth. I was told in my previous thread to continue to water and wait and see, and as of today (another week later), I'm seeing more dying roots and more visible mold inside the media. And another surprise is that recently, I also notice possible mold growth on the surface of the same exact media that is holding my bromeliad pup. I planted the pup in the same media 3 days after I repotted my phal. The growth looks like speckled, powdery white growth and its very visible on the black charcoal chunks and lava rock, and I also see this growth within the pot of my phal.

What should I do step by step now to save my first orchid?

Note: Not sure if it matters, but the new bag of media does contain a lot of charcoal/rock dust. Was I supposed to rinse the media with any solution or plain water first?

[estación seca]

It is usually better to use a more open, rinsed medium for orchids, so there are lots of air spaces at the roots. Orchid roots need plenty of air.

Hydrogen peroxide damages or kills roots. Then fungus grows on the dead roots. There are people who recommend spraying hydrogen peroxide on everything. Most of us here on Orchid Board strongly disagree. I think you may have killed the roots by spraying with hydrogen peroxide.

Don't use preventive treatments on plants. Only spray things when you know you have a problem, you know what the problem is, and you know the chemical you plan to use will handle that problem.

There is a great thread here on Phalaenopsis. From the left yellow menu select Forums, then Beginners. Look near the top for The Phal abuse ends here.

[Ray]

Some rootT loss is to be expected when you change potting media.

You might consider adding KelpMax to your watering regimen to "kick start" new root growth.

[ptk]

So I suspected that the new medium was the culprit since I still saw no issues with my other orchids in their original pots and media and the same fungal issue was happening in an entirely different plant with the same repotting medium.

I took the phal out of the pot and found so many dead roots due to fungus. I feel so bad for it since it started off with all healthy roots. I trimmed them off with sterilized pruning scissors. Luckily it still has its aerial roots and SOME live central roots. I washed the roots and trimmed off any ends that were mushy. You can see the before and after in the pictures attached.

I've purchased a bag of plain orchid bark from a different local garden store. The orchid bark is from a brand called Rexius and it apparently has already been heat treated/sterilized by the company and it's dust free compared to the other brand, so this one's giving me high hopes.

It's now sitting temporarily in a styrofoam bowl I could find to hold it. I've misted the aerial roots a little bit just a few minutes ago (7 hours after I washed it for trimming) since I was afraid of the roots drying out while it's sitting bare. You can see what it looks like now in the last picture.

The orchid now has basically 1/4 of the roots it started with. I now have a question about repotting this orchid with its now smaller root mass. The original pot it came in from the store was 4.5 inches in diameter. The 2nd pot I had it in was 6 inches in diameter and I definitely think another 6 inch pot will be too big. I have new pots with pre-made side holes that will deliver this Sunday that are 5.5 inches in diameter (I made the order before discovering how extensive the root loss is). Could I make it work with the 5.5 inch pot size? Or should I try to stuff it into a smaller container?

Btw, how is a root stimulator like KelpMax used, especially with an orchid that now has a majority of aerial roots left? Should I wait a certain amount of days after repotting before trying something like KelpMax?

[estación seca]

You cut off healthy roots. Just pot it up and let it grow. Stop using hydrogen peroxide. Stop watching whatever YouTube channel told you to do that.

[aliceinwl]

The roots that were cut looked dead to me. It still has a decent root mass. If you pot it up in good media and resume normal care, it should bounce right back. I’d also agree with steering clear of hydrogen peroxide and other “prophylactic” treatments.

[ptk]

Hi, aliceinwl.

Yep, those roots I cut off were definitely dead. They were rotten, black, mushy, and had fungal spores growing all over them. While cutting the pieces that showed obvious damage and infection I even double checked while running the roots under water, pinching around to find any more mushy, weak parts. Whatever is left in the last three pictures are the stiff and plump surviving roots.


After getting advice from other orchid hobbyists yesterday, I've already started the process of pre-soaking my new bark medium to prep for the 2nd attempt. And I'm glad to hear you're also confirming the viable root mass. I plan to pot it in a slightly smaller pot than what I first used this time. I really hope to get my first repotting experience right this time!

[aliceinwl]

For future repotting, roots with alternating mushy and firm sections should be left intact. These roots don’t seem to survive long-term but are still functional. I’ve really set some of my Phals back by cutting these (on purpose when I started out or by accident now). Luckily, Phals seem to be pretty forgiving and the plants bounce back once they can push some new roots. Good luck with your Phal!

[ptk]

Thanks for the luck and the nice tips!

I repotted the phal about an hour ago in the pre-soaked bark medium. So far so good. The roots look green and happy and is sitting sturdier in the new pot setting this time. It's been so resilient these past few weeks while growing a baby leaf and now recovering its roots. Thanks again!