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Avatar for Gabi567
May 29, 2020 7:31 AM CST

hi everyone!

I am keeping my macodes petola in a terrarium, which I open in the evenings when humidity is higher to get some air flow. It's a new plant and is in sphagnum moss which I keep moist.

it seems that the plant developed a white cast on its leaf. what could it be? does it need better airflow? It's my first orchid - thank you for your help!




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May 29, 2020 8:02 AM CST
Name: Big Bill
Livonia Michigan (Zone 6a)
GROW ORCHIDS!!!
Bee Lover Lover of wildlife (Raccoon badge) Orchids Region: Michigan Hostas Growing under artificial light
Echinacea Critters Allowed Cat Lover Butterflies Birds Region: United States of America
It looks like it could be powdery mildew.
It comes from humid conditions and poor air circulation.

How large is the terrarium?
I know of several people growing orchids in a Wardian Case which is similar to a terrarium. However, the Wardian Cases are equipped with muffin fans. These tiny fans keep the air moving.
Orchid lecturer, teacher and judge. Retired Wildlife Biologist. Supervisor of a nature preserve up until I retired.
Avatar for Gabi567
May 29, 2020 8:37 AM CST

Thanks Bill for your help! It's a 30cm x 30 cm mainly decorative terrarium for a 5cm pot plant, it's the only plant in it, but does not have the air flow indeed... Below is a picture of it from the producer, I will keep the main door open often to increase the air flow.

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I have also taken a picture of the roots. It seems that there is a part covered in black residue. I know that the previous owner kept it in an aquarium, could it be some sort of algae or is it root rot? I repotted it into fresh moss with some perlite and very fine orchid bark meanwhile, in case the old moss was causing an issue (it was very wet as well).

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May 29, 2020 8:57 AM CST
Name: Big Bill
Livonia Michigan (Zone 6a)
GROW ORCHIDS!!!
Bee Lover Lover of wildlife (Raccoon badge) Orchids Region: Michigan Hostas Growing under artificial light
Echinacea Critters Allowed Cat Lover Butterflies Birds Region: United States of America
Moss does degrade and go acidic. The wetter it is kept, the quicker it degrades. When it degrades it gets acidic which often leads to root loss.

The black discoloration could be mold, it could be fungal or just a discoloration due to anaerobic conditions.
Orchid lecturer, teacher and judge. Retired Wildlife Biologist. Supervisor of a nature preserve up until I retired.
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May 29, 2020 9:15 AM CST
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Name: Ursula
Fair Lawn NJ, zone 6b
Orchids Plumerias Cactus and Succulents Region: New Jersey Region: Pennsylvania Native Plants and Wildflowers
Greenhouse Ponds Keeper of Koi Forum moderator Lover of wildlife (Black bear badge) Adeniums
Do they still sells those small 10 $ computer fans? They would work perfectly in such an environment.

Yes, amazon sells them!
Last edited by Ursula May 29, 2020 9:16 AM Icon for preview
Avatar for Gabi567
May 30, 2020 6:32 AM CST

Thank you Bill for fantastic advice, I made sure now that the moss/perlite/bark mix allows more air into the roots as well, before it seemed to have been squished incredibly tightly in very wet moss, maybe for transportation.. I also used a bit of fungicide on the blackened root just in case.

Thanks Ursula, the computer fans are a great shout! I will order one and mod my terrarium!
Last edited by Gabi567 May 30, 2020 6:32 AM Icon for preview
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May 30, 2020 7:15 AM CST
Name: Big Bill
Livonia Michigan (Zone 6a)
GROW ORCHIDS!!!
Bee Lover Lover of wildlife (Raccoon badge) Orchids Region: Michigan Hostas Growing under artificial light
Echinacea Critters Allowed Cat Lover Butterflies Birds Region: United States of America
Your welcome
Orchid lecturer, teacher and judge. Retired Wildlife Biologist. Supervisor of a nature preserve up until I retired.
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