Is brown spotting and freckled leaves normal on Oncidiinae plants?

[krienschmidt]

Hi everyone, Just wondering if brown spots and freckled leaves is normal on my Oncidiums, Aliceara, and Brassia? I have several plants with spotted leaves, all in the Oncidium family. My Phals, Paphs, Phrags, Cats have none of this spotting. Still blooming, no leaf yellowing or loss just a lot of spotting. I never water from above and probably have less than optimal humidity. Seldom gets above 40%. Should I be concerned? Thank you for your help!

[rbarata]

I always have spots on my Oncidium family plants.
There are so many explanations online that I consider them all just theories and learned to live with them.
If you live in a warmer location in the US, put them outside from Spring onwards (don't forget to water them often if you do that).

[Dollythehun]

Agreed with rbarata. That's normal but water often. They are thirsty plants.

[krienschmidt]

Thank you, that's good to know. Yes, I have noticed a lot of explanations on line, none of which apply to how I care for them so I just kind of assumed it was the natural way of things. Just wanted some other opinions to make sure I wasn't missing something. I have been growing orchids about 3 or 4 years now but no expert by far.

[estación seca]

Everybody says it's normal. However, my Oncidium plants don't get spots. I sometimes forget to water them, and they get accordion leaves. My growing room is often too hot for them. The humidity in winter is often down to the 30%-40% range, though it is much higher in summer when I run an evaporative cooler. I heat the growing area in winter to a minimum of 50 F / 10C. This is one of my biggest orchid-growing puzzles.

[King_of_orchid_growing:)]

It is not normal for all Oncidium or Oncidium relatives. I have no explanation for it.

There are a few Oncidum or Oncidium relatives I own that do not have this problem.

How are the roots?

[Dollythehun]

Perhaps it would be more appropriate to say " it is a common problem."

[Ray]

That is a common problem, and indicates something is amiss with the cultural parameters they are seeing.

I have heard all sorts of theories about the source of the issues, from underwatering, to low humidity, to salts being accumulated in pockets surrounding stomata. All I know is that since adopting my current regimen of using pure water and very low fertilizer concentration at every watering (along with KelpMax and Inocucor once a month), frequent watering - humidity is not an issue for me- I stopped seeing the spotting.

[King_of_orchid_growing:)]

Originally Posted by Ray

...to salts being accumulated in pockets surrounding stomata.

Ray, I understand that this is something you heard and that you're not saying definitively that this is the cause, but I have to say this about this particular idea, and I know you'll get what I'm saying. Hopefully people will not misunderstand.

As far as I know, stomata are on the underside of leaves. Leaf spotting that is seen on thin leafed Oncidium show up on the top part of the leaf and the bottom. Anatomically speaking, stomatal pores do not go from the bottom all the way up to the top part of the leaf.

For this reason, I highly doubt the explanation for the cause of the spotting would be salts accumulating exclusively in pockets surrounding stomata. If this were the case, the spotting would only show up on the bottom side of the leaves, not the top.

Another thing that doesn't seem to fit with this explanation is that stomata are just openings. They are formed as a result of the guard cells. Guard cells are microscopic. If the salts are accumulating around the stomata, it would be affecting a relatively large area around it and would be affecting not only the guard cells, but other cells as well.

I'm not saying that high dissolved salts in water is not the cause. I'm saying that although it could be, I'm not sure if it is or not. However, if high dissolved salts are the problem, then I'm almost certain it is not just affecting the areas around the stomata.

[Ray]

Philip.

There are stomata on both surfaces of all orchid leaves. In the case of CAM plants - which I do not believe oncidiums are - there tend to be far more on the undersides that to tops.