These are somewhat new, the breeder took years to get Phaius and Calanthe intergentic breeding to hold a seed pod. So you may not find alot of info on them yet. I have a couple Krytonite, not that clone though. Phaius is a low light high water and Calanthe is a higher light and both need good drainage, terrestial potting mix. The heat is not the factor unless it is not getting enough water. They can take about Phal maybe Paph lighting, so your dappled sun for 4 hours sounds O.K. Are the roots still good? How often do you water and what kind of mixture is it potted in? They are also high feeder on the fertilizers but in weak concentrations. Too much sun normally will burn the leaves not just the ends. IMO it sounds like a root/water problem.

Thanks Tab, I'll try to sneak a peek at the roots. I have been misting them more because of the heat. It is in a orchid mix.

Phaius are hardly 'low light' orchids. Plenty of people grow them fully terrestrial in garden soil. I dooubt that they dig them up and look at their roots if or when they display sorry looking foliage. When grown in pots things are no different. In orchid mix the problem should be underwatering not over. I'll say it again. It is not possible to overwater a properly lighted orchid. If I water my orchids every single day of the week there is no more consequence than that I have spent far more time watering than might be strictly neccessary. The amount of light required is a LOT more than most people can normally supply through winddows. Unfortunately the reaction of most when their underlit plants start to yellow their leaves is to cut back on water. It is IMO the wrong response. Increased light, maybe also increased temps does more more quickly than cutting back on water, water which is probably already at the low limit for good plant health.

H

Hi
Am having a similar problem with a Flava x tank cross
I'm growing in straight sphag in full shade but is exposed to daily rains. It is growing like the proverbial weed but only on the new bulb. Older leaves get browns spots and then turn yellow.
I was thinking maybe too much water .?? I was advised by the seller to NOT use potting soil but I'm sure tempted to get it out of the sphag.
I'm not sure how many older bulbs are supposed to maintain leaves?? gary

For What It's Worth,

I grow my Phaius tankervilliae, outdoors in Maryland in FULL SUN whenever the temp is greater than 50°F. IF the light is bright, I water daily with a hose and nozzle. If it's cloudy, I reference the relative humidity. I grow in medium bark and styrofoam peanuts. I fertilize at least 3X/week, more as the light allows. These plants LOVE water and fertilizer that flow freely.

I don't think that Pt is very tolerant of temps in the 100°F + range. I will water but I won't fertilize at that temp. They rebound quickly!

--Stitz--

I see we are all over the map as to how to treat this apparently very unique hybrid. I still think when in doubt more light, not less but I also wonder if it is in orchid mix if it is not likely potted. A pot definitely puts a limit on how much water can be supplied and depending on the size of the plant it could be running out. We need much more information on the minutiae of location and general care from the grower. Is hose water being used on this plant? Has any feeding been done yet? As you can see too little information in the initial post can lead to endless speculation on our part.

H

More light for a Phaiocalanthe is not good. They are more low light than a regular Phaius. Phaius growing in full sun in zone 6 is not the same as one growing in sun in zone 9 or 10. I grow Phaius in the ground here in my area zone 9b-10a anything more than filtered sun will slowly kill off the plant. If you are growing it in full orchid mix than may be the cause. In zone 9 and higher that may not be enough water, they should be in a pro-mix are Spag. moss.

I have had my "ursula" for three years and it is having problems with dark brown spots. These spots seem to be some sort of "bug". Last year I cleaned all the leaves with rubbing alcohol and it did the trick - for a while.
It is planted in sphag moss and is watered when it feels dryish on the surface but moister under the top layer. It is in light and only direct light around 4pm.
Can any one help me with the 'bugs'?