It might help to keep in mind that sometimes a particular seedling is just a dud. And sometimes even an entire "batch" of seedlings from the same seedpod/flask/compot will be duds. If you're having success with 15 other Phrags, but just this one fails to grow or thrive, your P. lindleyanum might be on the losing end of the genetic lottery. It's also possible that the plant is diseased. While viral infection is very rare in slipper orchids, I thought I'd mention the possibility since lack of vigor is a potential symptom. I suppose it could be possible for long term fungal/bacterial infection or recurrent infections to cause issues as well.
I don't currently grow this species and haven't in the last 10 years, but when I did grow it, my plant did not appear to need any special care or attention compared to other Phrags. I treated it like every other water loving Phrag in my collection ... bright light, constant moisture, high quality water, and warm temperatures. Honestly, most Phrags will be fine in almost any type of orchid mix you give them, barring mounted culture. I'm not going into too much cultural detail (and you didn't really provide much info about your care routine), but to reiterate, if you're doing well with 15 other Phrags, then I think it's safe to assume whatever your growing conditions and care routine are, they are appropriate for Phrags. The only thing I can think of is that if your other plants are all hybrids or vastly different species, then perhaps they're a little more forgiving than a species (hybrid vigor is a real thing). The single biggest "tip" that improved my orchid growing (and especially my slipper growing) over the years has been to use high quality water, so that might be a route to investigate.
There are definitely some Phrag species with a reputation of being tough to grow or which have special requirements, but I don't really think of P. lindleyanum as one of those. If it's a species you're particularly fond of, you might want to buy another plant, odds are in your favor that it'll be a better grower if it's healthy when you get it.
|