Sorry to hear about this, it's the worst feeling to lose progress, especially pk crosses after you have seen them thrive.
My thoughts, are just that, my own.
- 'but I like to have things in clear pots so I can see the condition of the roots, so I repotted after the flowers faded.' - Repotted down size from Grow cubes to orchiata mix.
- 'actually this one was downsized to a 4" pot, the first time it was repotted, and is blooming again in this pic in that size. After this bloom, I did not repot, and it declined over a couple of months, so I downsized to the 2.5". The roots turn black and don't seem to grow green tips after the repotting, and consequently the leaves start to show signs of dehydrating.' Potted from Grow cubes to orchiata mix?
I think these two repotting events were probably not the cause, as you mentioned decline in the plant health before repotting. However, these two drastic changes possibly added to the decline. It's very difficult to change the media from something the roots have evolved into, especially when the plant might be on the decline. In my experience, it's easier to go from a dry media to a wet with existing roots. If I were to change media in the direction you went, I would have likely moved to an orchiata/ growcube mix for the first repot, then complete to orchiata the next repot. This decision would also weigh heavier on me if the plant was going into a decline.
- Temps / Humidity. I can pull up your other threads, but I recall your mid winter temps in VA are on the lower side of my own. Environmental conditions are completely different for everyone, but I have sustained root growth through the entire winter of newly repotted phrags, even kovachii. My Feb growing temps High 76, low 63 / Humidity High 82 low 60.
- Light and daylength: adjusted to 11hrs 30min at the lowest length in the winter, and back up to 12hrs now. LED full spectrum/ 1800W, 2 feet form the source on light rails. phrags don't seem at all picky about light, my mature plants can take high levels. Declining plants / newly repotted I have found do better with slightly lower light levels.
Probable initial cause?
- Mites. Something we have in common. We got hit with the same type of Mite this past year. I still have a mature cattleya that will not put out new roots or growths. I'm not sure how hard your two phrags got hit, or how hard you treated with Alcohol spray. Both the infestation and treatment might have impact on the growth rate of the plants.
- Growing temps: slightly warmer conditions would help a wetter media, cold and wet might promote other issues especially in organic media.
- Sterilization: Switch to MAP gas. Burn all cutting instruments. I have seen greenhouses that use only physan and still have virus when I tested their plants. If you don't kill everything you will likely pass virus, bacteria, fungus overall rot along in the collection. Bleach soak plastic pots, put clay pots into the oven 400deg. 2-3 hrs.. Sue Bottom has a great article on this in AOS or the St. Augustine orchid society website. Also test plants if they exhibit signs, doing a test of your entire collection every few years to weed out the virus. Especially if you are putting large resources into high quality plants. Drawback is testing is expensive. Last year I tested a phrag from another grower and found it had one of the two viruses. I was shocked, first phrag I have ever seen with virus.
Solutions:
- MY own personal steps I would take, given my temps and growing conditions defined above and the scenario you have presented.
- At this point, they have not done anything for months. no root growth, no new growth, nothing.
- First I would pull the plants out or exiting media rinse the root area, and spray the root area down with physan, while I let that sit I would put together a small mixture of root growth hormone. Rinse Physan off. then soak in
(great white: Great White PRPSGW01 FGGRWH-1OZ White Mycorrhizae OR Dip 'N Grow: Hydrofarm DG00201 Liquid Hormone Concentrate Hydroponic Rooting Solution)
and soak the bottoms of both for 5-10 min while I assembled the new media.
- I would run a test. One plant in a 4 inch plastic net pot and one in a similar sized aircone pot. Styrofoam peanuts at the bottom if you have them.
- both filled with grow cubes and perlite.
- Keep the media wet with RO. Keep them in a briskly ventilated part of the grow area, keep temp range in mind, and slightly off center from your grow light.
- I would use RO water to initially wet the media, then keep it wet with a spray hand pump of RO, not soaked.
- I would give it two weeks and see if any roots have started, once you see this a weekly shot of dilute dilute growth hormone around the media. and then increase watering as new roots push into the media.
- The difference in pots is to see if more air movement would help the root zone, having a difference would split up the plants, one with more air, one with more moisture retention. I'm not sure at this time which would be more helpful, so I would spread try both for my own knowledge.
Basically, that's what I would do given this scenario in my own collection, Really interested to see how others would approach this.
Pete