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Old 05-31-2019, 11:41 AM
Stella1979 Stella1979 is offline
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Join Date: Jul 2018
Zone: 11
Location: South Florida, Sub-Tropical :)
Posts: 23
Default Black Rot

Hi folks. Two weeks ago, I purchased 3 unregistered Cattleya hybrids at an orchid expo. These plants were potted in 2.5" pots containing sphag only and were very, very dry after their trip from California to South Florida. I suspected they'd been shipped this way and though the plants themselves didn't look dehydrated, I imagined they'd been dry for several days already so followed my usual plan for orchids that have been shipped... that is, I gave the roots an overnight soak, sharing water among the 3 new girls.

Next morning I unpotted them expecting to repot and that's when I realized I'd purchased the wrong size bark. (Cattleya potting for me is in clay pots containing leca and either orchiatta large or charcoal.) So, the plants were then bare rooted for a couple of days while I awaited delivery of media. During that time, they got another overnight soak. My thinking was that these very plump roots were accustomed to extended hydration levels having come from sphag pots and I was trying to slowly acclimate them to a more airy mix in which they'd be watered often. In the summer here in South Florida, my Cats can be watered every morning and will be dry by evening.

Okay, so a couple of days after coming home, the 3 plants were potted and got a normal 10-minute soak in feed water and following this, began the normal routine for cattleyas under my care... though thankfully, they were still being kept separate from my collection.

By day 7 with these plants, they displayed classic black rot symptoms. I treated by cutting away the rotten parts, spraying with hydrogen peroxide, and applying cinnamon to wounds. I did cut into what looked like healthy tissue but by day 9 or 10, the rot was back, so more surgery, then sprayed with Captan Fungicide. Still, the rot spread.

Last night, the sad remains of 2 plants went into the trash and the third is left with only 2 growths and one very sad root. So, finally, my questions...

My collection equals 30 varied plants. I have not experienced black rot before, but have only been growing for about 15 months. Did I give these girls black rot or could plants that appeared healthy at the time of purchase sneak this awfulness into my collection? Was it me, or them?

What would you pot what remains in? Here's what she looks like now.

Black Rot-2019-05-31-10-25-14-jpg

That root does not appear to be alive but it also has a stiffness to it that gave me a glimmer of hope. So, shall I go with my standard quick drying chunky mix to promote airiness in doing my best to ward off black rot? Or, should this plant that is in such danger of dehydration go into a more moisture retentive mix in an attempt to foster the growth of new roots?

I know I am not out of the wood with her yet, so my instinct is to go with airiness and careful watering until and if she shows signs of health, wait for root nubs (hopefully!), and then add a thin layer of sphag at the top of the pot to retain humidity a little longer for new roots.

What would you do in this situation? Shall I tell the seller? I fear that it was this recent purchase that brought black rot to my growing space, though I only have my word that this is my first experience with it as proof... and don't want to place blame on a quality grower if in fact the blame lies with me.

Last edited by Stella1979; 05-31-2019 at 11:43 AM..
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