Yellowing while developing sheaths

[Steve83]

Epc. Magic Wand (a SVO hybrid which I purchased locally), Dinema polybulbon, and C. aurantiaca, all started yellowing as soon as they began to develop sheaths.

Dpolybulbon.jpg - Google Drive

EpcMagicWand.jpg - Google Drive

C.aurantiaca.jpg - Google Drive


Everything else looks great, and nothing has changed as far as culture for them, which is as follows.

315w cmh
Temp 83f day, 69f night
Humidity 80-65% day, 70% night
Watering is usually 17 ppm N K-Lite 1-3x day (only the aurantiaca is in a pot), unless its a KelpMax or Quantum day.

I'm leaning to nutrient deficiency, but am not sure where to start.

[Orchidtinkerer]

I would start by raising your lights.

A 315 watt metal halide will be very strong. Find the right distance they can handle, once they have developed some roots in your care and have stored up some nutrients then you can experiment with increasing the light.

Even if you are feeding perfectly they need to adapt to their new environment and generally have no energy reserves straight from a shop.

If you are worried it is a Nutrient deficiency but don't know where to start here are some articles that might help:

A Guide To Feeding Orchids (Top 10 Tips)

Feed the orchids!: details of my fertilizer program for different genera

https://staugorchidsociety.org/PDF/C...ySueBottom.pdf

(PDF) Complete Guide for Growing Plants Hydroponically | Candra Wahyu Sportyawan - Academia.edu

[Roberta]

I'd doubt a deficiency... orchids really don't need much fertilizer, and you're dong it regularly (if anything, a bit on the frequent side but concentration is very low so should be OK). I am inclined to agree with Orchidtinkerer, that they may be getting a bit too much light. I see an almost-brownish band on one of the leaves, which can happen if the leaf gets too hot (which can happen if too close to the lights) I don't think any harm has been done (that slightly-toasted are may stay discolored, but the leaf is still good)

[SouthPark]

Originally Posted by Steve83

all started yellowing as soon as they began to develop sheaths.

Steve ------ how long had they been growing for roughly in that spot?

You mentioned all three started to develop sheaths, and the yellowing began soon after.

The other orchids are exposed to the same lighting condition too, right?

Has the growing area got gentle air-movement?

At the moment - what you 'could' do is to leave the orchids as-is. Don't change anything. It doesn't look 'bad'. If the orchids can handle it, then a little yellow-green is just fine. But if they get burned or continue towards becoming very yellow coloured ------ then definitely consider reducing light power.

[Steve83]

They have had these growing conditions since early August, and all have seen considerable development, even those which had root rot or have been mounted or repotted.

It's not light, because they actually get slightly less light with this configuration than the previous, and even my lower light/heat plants, like Gomesa crispa (which just wrapped up blooming, and I mounted last week) are doing great.

Airflow was checked with a piece of paper is is fine.

Yes, this is only happening to those developing sheaths. The Dinema has been constantly putting out new bulbs and roots for me.

tent.jpg - Google Drive

I have a small Oncidium Twinkle Pink Profusion, and that is now developing an additional spike. I haven't noticed any yellowing on it, beyond what it had when purchased (maybe a montha ago?)

[Roberta]

Wouldn't hurt, maybe could help, supplementing with a bit of magnesium (Epsom salts) If they don't need it , won't harm and if they green up you'll have your answer. (Others will have more experience with this as far as quantity goes, I grow under conditions very different from yours and have not had the issue)

[SouthPark]

Thanks for describing those conditions Steve. The setup looks pretty good there actually. I think Roberta's suggestion is a good one.

Do you occasionally apply weak mag-cal?

I really like this photo.

[Steve83]

I haven't messed with cal-mag, thinking K-Lite has good amounts of both.

I will try some waterings with P and K added (but still low ppm).

Thank you SouthPark. Here is a different view.

reds.jpg - Google Drive

[SouthPark]

Steve --- you probably won't need the mag-cal, as you're using k-lite already. Just keep monitoring. If the orchids just stay like that colour, then that should be ok.

Fantastic extra pic too!

[estación seca]

Epidendrum polybulbon and Cattleya aurantiaca are fairly low light plants in habitat. The Epi grows in moss on trunks of deciduous or evergreen trees. It is wet and shady all summer, less shady in winter. I have seen Cattleya aurantiaca flowering in Mexico in November in dense shade, growing lithophytically on a boulder in an evergreen forest.

Have you measured leaf temperatures? The last photo to me screams excessive heat and light.

I don't think the plant in the middle photo is getting enough water.