Yellowing of catt alliance pseudobulbs
 

I’m brand new to Cattleya alliance care, but I’ve noticed a couple of my plants have had one pseudo bulb yellowing and now one of those is also developing brown spots. I would love your help and experience. Most affected is the Blc Mini Song, and Blc Toshie’s Magic Doris

The plants joined me from Hawaii over a month ago so they are adjusting still. I am in Chicago, they are grown in an unobstructed southern window with full sun all day (not strong enough to burn leaves this time of year). Very dry inside and I noticed some pseudobulbs wrinkling, so I increased watering from once to twice a week with tap water(perhaps too often?) and one of those is supplemented with dilute Hausermann orchid fertilizer. The pottting media is course bark, perlite, free draining.

I do not supplement calcium or magnesium but maybe I should be (how to folks actually use epsom salt to do this?)

My instinct is I probably am overwatering and now that is rot I am seeing....Help, please! ❤️

I’m not 100% sure but here are a couple of thoughts:
Did you repot these as soon as you got them home a month ago? And how were the roots?

I’m wondering if the old root system might have gotten little damaged (therefore not taking up as much water as it should be) and that combined with the dry environment is getting a bit wrinkled.
Or, maybe the center of the part of the pot is staying too damp and causing some roots to rot. I can’t tell for sure, though, that depends on your growing environment, pot type, temps, type and size of media, ect...

Is the yellowing area squishy at all or is it still firm? And are the yellowing bulbs on the older growth or new ones?

Thank you so much for replying!! They are surprisingly firm and not squishy right now. I did not repot them as they were both in bloom when they arrived and I wasn’t sure if that would have shortened the flower life...or so they care about reporting? As for If they are new or old..I’m not completely sure

It's usually possible to observe the orchid to get some idea about which leaves look new or newest. If the bulbs associated with the newest leaves are turning yellow too, then that won't be a good sign.

Oldest bulbs eventually do become yellow, and dry up.

If any bulb goes yellow and brown/dark, and gets mushy, then that would indicate rotting activity. If you do notice such thing later, then the orchid should be removed from the existing potting media, so that the roots can be inspected, and the rotting region should be removed with a clean/sterilised cutting tool.

A systematic fungicide for orchids could then be applied. The cut regions should be given some time to dry and seal up, before finally repotting into clean media.

The main general recommendations for orchids of this sort grown using classical methods are : maintain natural air-flow (ie. avoid still-air environment); maintain comfortable temperature for the orchid; provide adequate duration and level of lighting for the orchid each day; maintain good air-flow around the roots and media inside the pot, which means good drainage pot and using a media that can retain moisture for some useful amount of time but won't become water-logged, and use a growing media that allows air to flow fairly easily through the pot; water adequately - as too little water can be problematic.

You're using course bark and perlite mix, which is absolutely fine. For this media, adjust your watering schedule appropriately to suit your orchids.

While once-a-week or twice-a-week might be ok for some growers in particular regions of the world, it might not be enough for other regions. It depends on just how quickly the media in the pot dries out in the place you're growing your orchids.

Generally, for repotting, unless the medium is really badly broken down, it is best to wait for new roots. When that happens varies with the plant (it depends on that species are in its background) Some are pickier than others... those that root more than once during a year are less touchy than those that do it just once. Especially watch Blc. Toshie's Magic .. it is half Blc Toshie Aoki, which is notorious for reacting badly to being potted at the wrong time. (It may do new growth at a very different time than new roots. It is the new roots that tell you that it's a good time to repot, which could be as late as next fall if it takes after Blc. Toshie Aoki so be patient)

I have a couple of Laelia purpurata x Pacavia crosses that did this same thing when I moved them to a location that got a little more sun exposure than they wanted this past spring. I moved them to a more shaded spot and subsequent growth has been green but the yellowed growths have stayed yellow (firm and fleshy with no sign of rot, just yellow).

Thanks everyone. Do you think it would be a good idea to take them out of the pots gently and inspect the roots to see what’s going on? Or could that cause more harm than good?

You can certainly do that carefully... just figure on putting it back if you don't see any issues. (No clean-up unless you see significant problems) You can also wait until after flowers fade just to not shorten their bloom.

For Catts, flowers don't last more than a few weeks. Waiting for those is not enough time to have problems get significantly works.
With Phals I advise potting in bloom or not since they don't seem to care, and also stay in bloom for months. One doesn't want to let problems develop for so long.