maxillaria rufescens with yellowing leaves

[heathersgoinnuts]

I have a maxillaria rufescens with yellowing leaves. Could this be a lack of calcium and magnesium or something else? I grow it under grow lights. I have it potted in bark and sphagnum moss. I water when it is almost dry with reverse osmosis water and 1/4 strength MSU fertilizer. Fourth watering I flush with plain reverse osmosis water. I have about 50-65% humidity in my grow space and 72-77 degrees during the day and 64-70 degrees at night.

[Dusty Ol' Man]

I'm not the expert, but if it were me I would reverse the fertilizer/plain water regimen. Except for certain types, orchids need very little fertilizer. Once every fourth watering should be enough. I'm sure someone else with more experience will chime in soon.

[estación seca]

That yellowing is likely caused by far too much light.

Also I don't think it's getting enough water. Most Maxillarias like to be moist to wet at all times. From IOSPE for this species:

"Found... on trees in wet tropical dense forests at elevations around 200 to 2000 meters...."

Wet tropical dense forests are wet, wet, wet.

[Roberta]

I also think it is much too dry. Keep it damp. Fertilize "once weekly weakly" at most, less is fine. I grow most of my Maxillarias in sphagnum to keep them rather wet (or small bark for the ones that are potted, but again, pretty wet) The light is also likely too bright, which also leads to drying that is too rapid.

[heathersgoinnuts]

Thank you so much! Now I know I am not watering it enough. When I started this orchid journey over a year ago I killed phals by watering too much How the tables have turned.

[estación seca]

Read about every plant you consider buying.

[Roberta]

That's part of the fun and challenge of orchid growing... learning the differences. You start with the general concepts, then fine-tune because they're not all alike. It really helps to research habitats a bit. And if you ever get an opportunity to visit orchids growing in the wild, you'll get insights that go far beyond what can be gained just by reading. Something to put on your "bucket list".

[Shadeflower]

The yellowing is too much light. You can tell because only the top leaves closest to the light have been affected.

Watering it more won't harm as maxilaria's like to drink a fair bit but these can also easily suffer from root rot so I wouldn't overdo it as the problem is the light not so much the watering.

Ps: It looks more like a cattleya than a maxillaria though...

[heathersgoinnuts]

Originally Posted by estación seca

Read about every plant you consider buying.

I do read and watch videos as well. I just feel like I am gonna overwater so now I tend to underwater.

---------- Post added at 06:57 AM ---------- Previous post was at 06:50 AM ----------

Originally Posted by Shadeflower

The yellowing is too much light. You can tell because only the top leaves closest to the light have been affected.

Watering it more won't harm as maxilaria's like to drink a fair bit but these can also easily suffer from root rot so I wouldn't overdo it as the problem is the light not so much the watering.

Ps: It looks more like a cattleya than a maxillaria though...

This had yellowing leaves when I got it a couple of months ago. But it is getting worse. The bulbs were very shriveled too. I thought it was a watering problem then but I guess I didn't hydrate it enough. I have had it further away from the light for a while and thought it was yellowing more because it wasn't getting enough light. Then I moved it to the shelf it is now with higher quality bulbs. It was still yellowing.

[Roberta]

If it was yellowing when you got it and you have had it only a few months, then it may not be due to your culture at all. If pseudobulbs were shriveled, that sounds like a root problem that it came with, underwatering may have contributed though. One thing that I have found about Maxillarias in this section (and it IS a Maxillaria...), they do make new growths readily, drawing energy from pseudobulbs that may be leafless and even rootless. Just be patient.