Yellowing while developing sheaths
 

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.

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

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)

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.

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?)

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)

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.

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

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!

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.

As orchids go, most inflorescences are very fast growing, compared to the rest of the plant. That means a lot of nutrients are being funneled to those tissues.

My first thought was that you should try Epsom Salts - a single watering with 1/8 teaspoon/gal ought to show some greening shortly.

Then it occurred to me that they might be drying out rapidly, so the absorption opportunity is fleeting. If that's the case, watering more often at the current fertilizer concentration might be the key. ES' observation supports that. Alternately, you might consider "upping" the fertilizer a bit - maybe 50% more than the current amount. There is no danger of overdoing it at such rates.

A few questions:

1. What is your water supply?
2. How long have the plants been getting the current feeding and watering regimen? (I know it hasn't been very long.)
3. What were they getting previously?
4. Are you using KelpMax more frequently than monthly or at a stronger concentration than 1:250? (Incidentally, there is no issue with applying it or Quantum with fertilizer, or all three at once.)

ES, yes I've checked leaf temps, and keep broms at the warmest area as an indicator of sorts.

The aurantiaca has been doing great as far as hydration, and the old bulbs haven't displayed any shriveling. I do plan on mounting it once flowering is done, so I can get more air to the roots, and have one less pot to deal with.

---------- Post added at 01:08 PM ---------- Previous post was at 12:06 PM ----------

Ray, I fed some P and K last night, and will add some epsom salt to today's waterings.

1. RO city water, with dechlorinator added. I check ppm on every 5gal fill up, and its fine.

2. approximately 45 days

3. The Dinema and Epc were fed MSU weekly at a higher ppm than I fed. I also mounted the Epc about two weeks ago becasue It wasn't breathing well in the pot. Its older bulbs are better hydrated thatn when I purchased. I don't know the prior culture of the aurantiaca.

4. KelpMax has only been applied monthly at 4ml to 1 Liter RO water.

My watering consists of spraying the roots of the all the mounts first for a few seconds, hitting the potted stuff, spray mounts again, spray broms, spray mounts.

This occurs at 8:00am, and is often followed by another watering later in the day with what is left in the sprayer.

I decided to create a set schedule in google calendar last night, so every supplement/nutrient, and it's mix ratio is pre-planned, and repeats per instructions.

I am going to give additional amounts of Mg, P, and K over the next few days to see if this subsides

I can't imagine Ca is the issue, as things that are growing quickly, display no typical signs of Calcium deficiency. These Myrmecophila pics are dated 9/15/20 and 10/6/20. Note how plump the old bulbs have gotten, in addition to the new bulb growth.
Myrmecophila9/15.jpg - Google Drive

Myrmecophila10/6.jpg - Google Drive

All the broms have been pupping as well, and show no signs of deficiency, just lots of red lol.

The plants look good but some of them may be infested with spider mites.

I checked all the plants, and no spider mites.

I have some positive updates.

Light intensity, somewhat, by covering the opposite side/corner in poly sheeting. I also divided and unpotted some broms, and attached them to some plastic mesh I zip tied.

plasticforest.jpg - Google Drive

With what I was seeing among my plants, I believe I have narrowed the deficiency to Mg, P, K, or some combination.

Interestingly, my Onc. Twinkle Pink Profusion, which was purchased with one spike in early September, produced another early last week. The stem on the second spike is noticeably larger in diameter.

OncTwinkle.jpg - Google Drive

Yesterday, I noticed it was finally starting to show some yellowing as well, and to my surprise, I found two more spikes forming (both of larger diameter).

Since this was first reported, waterings have been with K-Lite @ 25 ppm N with either P and K, or Mg added.

All of those listed have begun to slowly green up. I'll continue with this regimen, and keep my fingers crossed.

Even if things resolve, this layout isn't ideal for repeating on the opposite of the tent becasue it's just too cramped. I most likely will have to bump up to a 4'x4' tent with a height extension before adding anything else.