What could this be? - Oncidium with white veins and curled leaves

[rbarata]

White veins on leaves, maybe not so noticeable in the photo.
This plant is growing fine, with this new pbulb and lots of new healthy roots.

It seems some kind of nutrient or environmental deficiency.



Curled leaves

[Dollythehun]

The leaves in the first picture look silvery, did you check for mites? Pleated foliage usually means it needs more water, my educated guess would be the same for curled foliage. I know lately my oncidiums are water hogs, they could sit in water...I think the last picture looks fine. What kind is it?

[rbarata]

I only know it's an oncidium...my mother brought one pbulb last year from Madeira Island and it's been growing fine. It never bloomed, I think it's too soon yet.
The curled leaves might be due to low HR (it has been between 20 and 30% during the day). I'm watering more now.

I just checked for mites now and the cotton comes clean.
Some more photos to help.

[Dollythehun]

I'm going to show my ignorance here. Some of them are thick leafed, like the old mule ears, and some​ thin leafed.
My thicker leafed ones do sometimes throw a leaf that is a little 'wonky' and their foliage is often less than perfect. In my opinion, I don't think you need to worry.

[Sharon's Sheepdogs]

Leaf curling in an orchid usually means 1.) pests, as dolly indicated 2.) Overwatering or 3.) Fusarium Wilt.

Before you jump to the third possibility, you have to rule out the other two first since it is not likely to be fusarium. I don't grow oncidums but I did find a previous post on this site involving an oncidium which developed leaf curl.

As Dolly indicated, oncidiums can be water hogs. Well, apparently if you are not providing sufficient light to the amount of water you are giving the oncidium, its leaves will curl. You can find this info here:

Oncidium leaves are curling

Is this a possibility?

[Dollythehun]

Sharon, notice in the OP, he is pushing lots of new roots. I still think it's a water issue. It's been bright here and some of mine need water every day.

[Sharon's Sheepdogs]

Good point Carol. I would think that providing only 20% to 30% humidity level would be too low which is what is being provided per the original post. This would allow the Oncidium to dry out too quickly. Usually dehydrated leaves become pleated but maybe they curl in Oncidiums. However, the Oncidium apparently has good root growth despite low humidity.

Perhaps it is a nutrient deficiency. I forgot to include in my previous post that leaf curling/cupping can also occur if there is a Magnesium Deficiency. Another symptom of Magnesium Deficiency is blotchy leaf colors which this Oncidium is developing.

A nutrient deficiency is what the OP originally thought might be the problem. For more info on this possibility and how to correct it, see Sue Bottom's article at:

Orchid Environmental Damage

[Dollythehun]

I saw that defiency in my phals but, it took years to show up. I started using Cal mag with my fertilizer. I have never noticed it in the oncidiums so, I would be ignorant as to how that looks.

[rbarata]

I'm a watering conservative guy so I will make an effort and increase the watering. I always use fertilizer with my orchids so I'm assuming Mg deficienty might be a cause, especially due to the high light levels of the window where it sits on.

Reading the article that Sharon posted, Ca is used to construct cell walls. Since it is growing fine, probably this isn't a cause.
By other end, Mg is used in chlorophyll production. If not enough, the chlorophyll production rate is not enough considering the light levels. Hence the blotching on the leaves.

So, because the light levels are correct, the solution is to increase watering, always with fertilizer.

If this won't fix it, well....maybe some other disease.

[estación seca]

Whenever I see uneven chlorophyll distribution I think of magnesium or iron trouble. It shows in different kinds of plants in different conditions. I have read Vandas display magnesium deficiency during cooler weather by turning purplish. The purple tinge disappears during warmer weather in these Vandas.

Magnesium has to be present in water or potting medium; it has to be taken up by the plant; it has to be transported to the developing leaves; it has to be incorporated into chlorophyll molecules.

Iron is used by the plant to make chlorophyll. It also needs to be present, needs to be absorbed and needs to be transported to the leaves.

If your water supply and potting medium lack magnesium or iron, that can be remedied by supplementation. What is sold in the US as epsom salts has plenty of magnesium. I have read of people adding 1 tablespoon / 30ml of epsom salts to a gallon / 3.8liters of water for magnesium supplementation of orchids without problems.

I have read almost nothing about iron deficiency in orchids. I don't know what to make of this. Maybe epiphytes are so good at scavenging tiny amounts of iron they don't need much? Many other kinds of tropical plants needing neutral to acid soil rapidly develop iron deficiency and yellow leaves in cultivation with alkaline water. Iron deficiency is more likely to cause this chlorosis in other kinds of plants.

Magnesium salts are often not very soluble in water, so it is often better to give it separately from other nutrients. Plants absorb magnesium best in a narrow range of water pH. If your water is alkaline your plants will have trouble absorbing magnesium.

Plants also need a full complement of their enzymes to produce chlorophyll. Enzymes are proteins, made of amino acids. Plants need nitrogen to make amino acids. So under some circumstances yellowing leaves can be caused by inadequate nitrogen - usually when plants are growing rapidly.

Magnesium is not transported through the plant rapidly, so it can take months to correct magnesium deficiency.

Finally, as to water for Oncidium hybrids... these are not orchids that should get dry between watering, especially in a low-humidity environment like the Iberian Peninsula or Arizona in springtime. They dislike that very much. If they're only dry for a day or so between watering, they won't die quickly, but they look terrible and just sit there. If they are allowed to dry out completely for several days between waterings they decline and die.