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Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous
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Old 11-12-2021, 08:25 PM
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Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous
Default Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous

Ok I was debating writing about this and I got into the mindset of not wanting to share my experiences because so many people online just like to dissect everything you say and like to add their own criticisms without appreciating what is being shared. I take some criticism's badly at times like telling me I can't breed certain orchids or that I lack the qualification to talk about orchid growing. Well the inventor of starlite took his secret to the grave because he thought the £2 million offered by NASA was an insult to his invention so he never sold his breakthrough invention at the time and never made a penny from his invention taking it with him to his grave fearing if he sold it it would be copied.
Starlite has never been able to be replicated by any scientist since. He was a hairdresser by the way.
So instead of taking my discoveries with me to the grave like him I will post about it and risk getting thrown out of the science lounge like Galileo before me for proposing the earth revolved around the sun. I am aware I will wake up the grumpy fertilizer people that be but so be it. I am aware that I am posting about groundbreaking theoretical and unheard of orchid information but that is how new theories and eventually facts are formed. Take Roy Tokunaga from H&H orchids. I believe what we know about calcium and magnesium is down to the discoveries Roy made on the subject.

So as we know there is much debate among orchid hobbyists on what our orchids need or don't need. I want to address one that has been bugging me for a while: red marking on orchid leaves.

Now most often this happens when you place an orchid into high light and if you move the orchid to lower light then the reddening dissapears.
The consensus is that too much light causes increased anthocyanin production which protects the orchid leaf like a suntan protects from high UV radiation thus the orchid leaf turns red and lowering the light reduces the reddening.
Although this is what happens under high and low light I do not believe that lowering the light is the answer or the solution. It's like slapping a band aid on the problem and calling it job done like a mechanic telling you that your broken headlights are only a problem when you drive around at night so the solution is to only drive during the day! Ok that "fixes" the problem but replacing the headlights is the proper fix to the problem. I also believe that although the reddening protects the leaves from UV damage it also lowers the photosynthesis the leaf can perform like placing some sunglasses on the leaf.

I know people have been growing for years and years and are happy to believe to just lower the light, job done. Motes mentioned one of his grower friend had thrips for over 20 years and was oblivious to it. He could never see them and the damage was not too noticebale with regular flushing the thrips out of the pots. But wouldn't it be better not having thrips? They do so much hidden damage nibbling on every new root tip causing a lot of stress which can incidently also cause reddening leaves.
As mentioned in the title cold can cause reddening to appear also.

Ok so should we just lower the lights and accept nothing can be done to alleviate the "stress" symptom? Lowering the light will reduce flowering. So my challenge has been to discover what and if anything can be done about reddening/purpling leaves without lowering the light.

I should add as a disclaimer that it is very hard to differentiate between different problems and so many can look alike so no visual assessment can ever conclusively be used to determine a problem, you'd need to perform a full scientific analysis of the orchid but thats out of my reach so visual observations it will be.

Before we start to delve deeper into the rabbit hole I will add a quick basic 101 on fertilzing orchids:

Understanding Orchids: An Uncomplicated Guide to Growing the World's Most ... - William Cullina - Google Books

https://www.vancouverorchidsociety.c...ber%202016.pdf

Ok so lets begin.
One theory out there is that reddening on leaves is caused by a lack of magnesium according to Motes: https://static1.squarespace.com/stat...ing-sample.pdf
Increasing the light will increase the growth rate of orchids but will also increase their demand for water and nutrients. This would explain why the reddening increases with more light and decreases with less light. Although decreasing the light improves the symtom it would only be so because the demand has been lowered and thus supply does not run out as fast.
So it is one way to approach it but lowering growth will lower flowering so instead of reducing light I thought I should investigate if increasing magnesium would alleviate reddening leaves seen by increasing light levels as mentioned.

Ok so in order to test the theory I added epsom salts to a few test subjects that were developing reddening leaves under high light. Initially I had just reduced the light but for the test I kept them under high light and tried magnesium in the form of epsom salts. I did see a slight improvement but nothing spectacular that gave better results than just lowering the light.

After a bit of research I concluded that magnesium deficiencies should only affect older growth, reddening on leaves appears on the top of the plant closest to the light where all the new growth is being developed. So after trying magnesium I have concluded magnesium does not alleviate the reddening of leaves caused by high light.
Ok but I was not done with the experiment, next I had read a lot about all the different nutrients and a possible candidate was a phosphorous deficiency.
I know traditionally a phosphorous deficiency is very rare but I believe it is far more common in orchids than people realize.
I believe 90% of magnesium deficiencies on youtube are infact misdiagnosed phosphorous deficiencies.
This is based on my own observations and the fact that a few new fertilizers like the MSU formula which I started using this year have a very low Phosphorous content. (13-3-15-8-2)

As we can see in any concentration, the amount of magnesium and phosphorous will be lowest out of all the macronutrients. So those are the most likely candidates if it is indeed a deficiency like I was suspecting. Even if the incidences do occur more under high light and stress.

I ruled out magnesium, that leaves phosphorous according to this AOS article:

https://www.aos.org/pdf/AOS_8_Fertilizing%20.pdf

Other articles to support this theory:

How to Read Your Plants and Prevent Problems in the Garden

https://www.gardeningknowhow.com/pla...ish-purple.htm

https://www.cropnutrition.com/nutrie...ent/phosphorus

this is the only picture of a phosphorous deficiency I could find online:
https://staugorchidsociety.org/PDF/F...ering-Wang.pdf

https://eurekamag.com/research/002/815/002815477.php

https://www.ishs.org/ishs-article/878_41

https://cropnuts.com/plant-nutrient-...ide-for-crops/

Ok so armed with this wealth of information I went out and performed the hard task of buying a phosphorous fertilizer. My local hydroponics store had plenty in stock.

And then for the testing. I increased my ratio from 12-3-14-12-3.5
to 12-7-14-12-3.5 so doubling my phosphorous. I saw much more improved results compared to the magnesium test.

Like I mentioned this is just a visual observation and it is hard to see the changes without seeing them in person. One should also not ignore reddening leaves by increasing light too much. It is a stress response from the plant and feeding more takes time so exposing an orchid to too much can be detrimental. It is best to reduce the light, reduce the consumption and growth of the orchid, ammend the feeding and increase the light after the orchid has had time to recover.

this is a healthy new growth:

this is a clone of the same plant with a deficiency:

here is a cattleya that is lacking something:

Does it affect neofinetia's or is this genetics? Still to be confirmed!


new growth on this dendrobium started off very purple:

this mini catt and others started off growing slow and red:


Ok now after I started adding Phosphorous:
the newest growth on the dendrobium has turned green:

the growth on the mini-catt is growing well and greening up:

then a phalaenopsis comparison:


The next picture is maybe hard to interpret but has been the most obvious to me watching it, you have to understand how an oncidium twinkle grows, it grows a long flower spike first, then once that is grown it grows little side spikes like a christmas tree, then little balls like baubles develop on these spikes that turn into the flowers. So once the spikes had grown and looked very red I started applying more phosphorous compared to the other macronutrients. I think the result speaks for itself:

and finally a vanda at 1 month difference with the deficiency dissapearing slowly:

Hopefully this helps others if they encounter red leaves in future. It does not necessarily mean you are providing too much light, if the leaves are not developing sunburn then they can handle more but if the reddening progresses too much the plant will become depleted so reddening is a warning sign that should not be ignored. It might not even be phosphorous related at all either. I mentioned thrips, it was most likley to occur on plants affected by thrips actually so maybe the thrips were damaging the roots and the orchids could not absorb nutrients as well as unaffected orchids!

If it helps I have taken pictures of further suspected symptoms of phosphorous deficiencies that do not display as red or purpling, several different varieties will display sympoms differently. Vanda's usually show the "reddening" symptom but others might show leaf curling, leaf necrosis and darker lower leaves.














These should not be confused with calcium deficiencies which are explained here for difference:

https://plantprobs.net/plant/nutrien...s/calcium.html

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

https://academicjournals.org/journal...f/FBBEB0636258



also a magnesium deficiency for reference:
https://myorchiddiary.wordpress.com/...cy-in-orchids/

and a suspected iron deficiency:
https://extension.arizona.edu/sites/...ubs/az1415.pdf




conclusion:

So I mentioned these problems were observed trying out a new low phosphorous fertilizer, the MSU formula to be precise.
I wasn't planning on this being about MSU but in hindsight I cannot leave out that information. The MSU formula at 13-3-15-8-2 has been designed to have low P.
So what does this mean, is the MSU formula no good for growing orchids if they develop deficiencies?
I believe the answer is yes and no.
The reason there is no straightforward answer is because the MSU formula works great on hybrid phals where pretty much any ratio works, they have been bred to grow on a wide range of formulations. The low P formula will not show deficiencies on all orchids. Only some.
What makes the matter even more complicated is the way I grow. I know I am partly to blame where another grower would not have encountered the same issues.
The reason is that I essentially grow my orchids in a recirculating hydroponic way. What this means is that all the water I feed is used by the orchids, none is wasted and none gets flushed out.
This is not the recommended way and if one doesn't feed correctly then it is far more likely to cause problems than feeding the traditional way.
The best way to water and fertilize orchids is to give them a heavy feed – more than they need and then an hour later flush out the excess with plain rain water. This allows the orchids to pick and choose what nutrients they need at the time and the rest is flushed out the pot.
Like a kid in a candy store the orchid can pick whatever it wants to the most and the rest is then flushed away.
If on the other hand you use a recirculating hydroponic way of growing then all the water you feed is used up by the orchid and if there are any "sweets" left over the orchid needs to eat those too.
It can't pick and choose, everything I feed it the orchid has to absorb. I do not flush my pots and I do not let excess run out like in S/H.
So maybe that is my "problem", it is certainly a factor but I am not going to start regularly flushing my collection, it just isn't going to happen for me so I will have to tweak my ratio's till I've found what gives the best results.
Most growers who feed and flush will most likely never experience deficiencies seen in these pictures because the plant will naturally select the nutrients it wants and needs to grow best. It has the choice if you feed a bit more than it needs and an hour later flush out the rest. So most likely most growers would never experience a problem using the MSU formula.
Now the reason it might be a great formula would be for the formula one orchid growers. Those that compete in orchid shows and where every benefit is needed, some believe orchids can produce better flowers by tweaking the ratio and feeding a "bloom booster" at the right time and then increasing growth by using a formula designed to produce the best growth the rest of the time. This is where the MSU and other "non-balanced" feeds come into play. If you are an experienced grower you might prefer to use a grow and bloom formulation but honestly I think it is confusing. I did not realize that only using the MSU formula would give me problems. I was under the impression it is the best all year round formula to use but it isn't. You have to use a blooom booster with added phosphorous if you are planning to use a low phosphorous fertilzier the rest of the year. Otherwise you might encounter a deficiency, maybe not, it depends on the circumstances but my belief is that the MSU formula should be ammended with a bloom booster which I did not know when wanting to try the "latest best thing".
So if you don't want to risk knowing when to add a grow fomula and when to add a bloom formula which imo won't make much difference to the hobby growers results then I would recommend you stick to the tried and tested and widely recommended belief to go with a balanced fertilizer like 7-7-7 or 20-20-20
Yeah it possibly can be tweaked by the formula one growers amongst us who might get 21 flowers instead of 20 but for the average hobby grower I would highly recommend to stick to the balanced formula which will provide the best chances of feeding all the orchid needs all the year.
There is of course the belief that too much Phosphorous can build up in the pot over time and is hard to flush out which is why the MSU formula was probably designed in the first place but they went too low imo. Instead of 13-3-15 it should be 13-7-15 at the minimum imo.

I cannot comment whether a 13-13-13 fomula would work better than a 13-7-15 fomula or vice versa but I can say with this post that 13-3-15 in a recirculating hydropnic system will cause a long term phosphorous deficiency.
It also took a minimum of 6 months for symptoms to start showing.

Ok I know this is a handful to take in.

Like said I know not all will agree with this conclusion and I welcome anyone to do their own experiements. I know I have come across a lot of articles saying other things and the articles I did pick for this post were "selected" to support my hypothesis. There are plenty or articles that would not support it.

So full disclosure on that, there are so many theories one even can find evidence of sugar being a great nutrient to use. Well it is actualy used in orchid seed growing media as a main ingredient
But yes there can be lots of arguments found against these conclusions. I am not here to have my observations nit picked and pulled apart. If anyone wants to make their own observations then by all means I'd love to see other people's counter experiments. Otherwise hearing how I am not qualified to make these assessments or the formula was designed by scientists and I am not a scientist doesn't really help the orchid community does it?
I have made these observations and I am sharing them. That's it. You can take it or leave it. Grow with cow manure, use egg shells. There are many different ways. This is my way and most will know we all grow a bit differently.

I know some will use this in future to maybe claim I am a bad grower who grows purple looking orchids so I do want to point out it is a minority of my collection that is affected and as soon as I noticed I had a problem (which is hard to tell as everyone would tell me it was just too much light) I tried to fix things. I think I have managed to fix things and I want to share my obserations so it doesn't take others decades to figure out maybe they are providing too little light, maybe they are fertilizing wrong. Or maybe this is all nothing. I love seeing others post their orchid growing journeys like herebutnot has so this is a little tidbit from my garden. Happy reading! And growing of course.

Last edited by Shadeflower; 11-12-2021 at 10:35 PM..
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Old 11-12-2021, 09:01 PM
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Excellent post shade. One paper I came across regarding pigments due to relatively high light is at this link.

Have definitely seen the purple with new growths on catts in relatively low light too. Some of them. Not all of them - aligning with your observations. I just assumed it was normal, as the orchids just kept growing normally.

Absolutely welcoming your post here. Nice one Shade.
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Old 11-13-2021, 09:46 AM
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Thank you Shadeflower for a well thought out, objectively written article (I'm hesitant to call it a post anymore, given the length). I have not yet gone through all the links you attached, but it's good rainy saturday afternoon reading.

I appreciate your scientific approach to the problem, doing a desk study, formulating hypotheses, and then testing them on your plants. You'll likely get comments about the sample size and 'anecdotal' evidence, but one has to start somewhere, and your conclusions sound very plausible in your described situation.

Could you explain your recirculating hydroponic system? I was under the impression that you were growing your plants in pots with a wick system. Are the wicks hanging in a recirculating nutrient solution? We face the same challenges at work (an indoor farming company) and we have to do weekly water analyses and regularily have to 'top up' certain nutrients. Like you say, some nutrients are candy to plants, and for others the uptake rate really depends on the type of crop in the pond.


I really don't want to turn this thread into a heated debate about MSU, but I'm still very much undecided about fertilizers. I used a balanced 20-20-20 for a long time before switching to Rainmix. I didn't set up a proper experiment, but my feeling has been that the 20-20-20 gave better results in terms of growth, spiking and flower count (note that my collection is 80% Phals). I have spent quite some time looking up scientific literature, and in commercial production, it seems that having Phals benefit from being fertilized with high P levels, some articles suggested that P be supplied in a similar amount as N. I may grab 2 Phal mini flasks from Roelke one day and run a controlled experiment.
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Old 11-13-2021, 12:18 PM
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Shadeflower, I think that is an excellent post, but there are so many different aspects of orchid nutrition that are intimately connected, that I think it's hard to draw any solid conclusions.

Most of the "knowledge" about nutrition is gained from studies about food crops, then extrapolated to orchids. If you look at the immense variability in the "proven" (by statistically-significant scientific studies) nutrient demands within food crops, I really don't know how extrapolating that info to orchids can have much validity.

For example, high potassium has shown to be essential for getting the most yield out of rice, but that as not shown to be the case with many other plants. Similarly, we might conclude that nitrogen is the most important nutrient in terms of mass required, yet if given to carnivorous plants, it can kill them.

Your hypothesis is that red pigmentation is a bad thing, as it reduces the rate of photosynthesis. Do we really know that? We must not ignore the fact that chlorophyll is not the only energy-absorbing pigment in plants; the carotenoids like beta-carotene and lycopene (orange and red, respectively) are players in that process, as well. Maybe at different light levels the relative development of which pigment changes, but that doesn't necessarily prove anything about which is better.

If I accept your hypothesis that red pigmentation equals less efficient chlorophyll-based photosynthesis (which I do, based upon "sunglasses" logic, not scientific proof), might it not be possible that the red pigmentation completely compensates for that? I don't know the answer, but it's something to consider.

Then there's the Martin Motes example you used. In that the red pigments were produced with a reduction in temperature, not with a change in the light level. He states that increasing the magnesium is a way to correct for that, but I see no proof that doing so is necessarily worthwhile.

That makes me wonder if the "high light" and "too cool" pigments are the same? Do we know which is anthocyanin and which is a carotenoid? Could it be one, the other, or both?

Then, of course, there is anecdotal evidence that contradicts the "historical concepts" and conclusions.

The MSU RO formula has been around commercially since 2003 (with the EU "Rain Mix" version following that), and a lot of folks have been very successful growers using them.

Then there's K-Lite, which is about to hit it's tenth anniversary in the marketplace, and at 1.3% each P & K, based upon your conclusions, it should be horrible, yet there are many getting great plants with its use, too.

I have heard from PhD's in plant nutrition that orchids are particularly demanding of magnesium. My own experience using RO and now tap water that contains none, suggests that's correct (when I've gotten lazy about feeding), but we don't know what concentration is good and what's bad. (Too much Mg can interfere with plants' incorporation of Ca and K.)

What it all comes down to is try to find a point that is neither deficient nor excessive.
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Old 11-14-2021, 02:49 PM
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SP, thank you.

Quote:
Originally Posted by camille1585 View Post
Could you explain your recirculating hydroponic system? I was under the impression that you were growing your plants in pots with a wick system. Are the wicks hanging in a recirculating nutrient solution? We face the same challenges at work (an indoor farming company) and we have to do weekly water analyses and regularily have to 'top up' certain nutrients. Like you say, some nutrients are candy to plants, and for others the uptake rate really depends on the type of crop in the pond.


I really don't want to turn this thread into a heated debate about MSU, but I'm still very much undecided about fertilizers. I used a balanced 20-20-20 for a long time before switching to Rainmix. I didn't set up a proper experiment, but my feeling has been that the 20-20-20 gave better results in terms of growth, spiking and flower count (note that my collection is 80% Phals). I have spent quite some time looking up scientific literature, and in commercial production, it seems that having Phals benefit from being fertilized with high P levels, some articles suggested that P be supplied in a similar amount as N. I may grab 2 Phal mini flasks from Roelke one day and run a controlled experiment.
Camille, you are correct I just use a wick in a pot, that is my system. But I have noticed that over time the nutrients can accumulate or get lower in the pot depending on the plants demand. Like in winter the plant carries on drinking but takes up less nutrients so then the ratio of water to nutrients changes and if one carries on feeding too much then the concentration can rise too high. I think I would like your job.

I have come to similar conclusions about phals from all I have read. Phals seem to be a bit unique but it might just be a case of monopodial vs sympodial orchids having different requirements.
So Vanda's and Phals would prefer lots of more blooming aligned fertilizers and Cattleya's seem to prefer a 1-0.5-1 ratio but I don't want this thread turning into a debate on that because those debates focus on flowering and like I mentioned I just do not have the experience to comment either way.
I want to make it perfectly clear I am far more interested in the overall health of my orchids.
I have to admit I have never really understood bloom boosters too much, when to use them, why to use them and the theory always revolves around using bloom boosters to improve blooming but that is a confusing way to look at bloom boosters. I think they have a place in orchid growing, orchids need more phosphorous when making new growth, for root production and flowering.
This is what I have observed and I would add insect stress too. That really pushes their demand up...
So if your orchid is pushing out 5 flower spikes and you don't supplement with a bit more during this time, then under high light chances are you will see some nutrient depletion in the leaves. So during these times it is beneficial to feed more phosphorous just so that no deficiencies occur.

I will also add that I did try just increasing the overall nutrient strength of my feed but that did not produce favorable results, roots stopped growing, it was just too strong.

So that is an important note to add, one doesn't want to overload the orchids, bloom boosters are formulated to be very strong, one should always think about the overall ratio of nutrients. If one normally feeds with a 7-7-7 feed and one gets a 0-40-50 bloom booster that bloom booster is much much more concentrated so even just a drop of that added to the regular feed would be enough to a gallon.

I don't want anyone to get the idea of overdoing it with anything I am saying here.

Ray, I want this to give others something to think about. I know you favor k-lite but I still want to see a side by side comparison if someone can do it. It would have to be a minimum of 1 year which makes it challenging and the orchids would have to be in identical condition to start with.
I consider K-lite to be a 1.3-1.3-1.3-10-3 feed + 9-0-0
It is a theory that in bark when it degrades it can use up the Nitrogen so in bark a high Nitrogen feed has been thought to be beneficial.
If you look at it like that then in bark the K-lite might be perfect. It has a high amount of micro nutrients to macro nutrients. I only know one other feed that has a higher ratio.
Some consider that to be the most important factor. I have been upping my iron and other micro nutrients and have seen some good improvements.
So in bark who knows, maybe K-lite is good but too much Nitrogen can inhibit flowering long term. That is not what I want to discuss here.
Unless someone has a good sidebysside with lots of pictures

One thing i will add and I think I have observed by now is that I believe upping the phosphorous has increased the orchids demand for magnesium.

I think this is where a lot of problems might come in to play.

If you suddenly apply a bloom booster and don't supply an equal amount of magnesium at the same time then the plant might become deficient in magnesium instead.

If you look at Rainmix, it has more magnesium than phosphorous.

If you look at k-lite it has more magnesium than phosphorous.

We know you can't start adding lots of nutrients separately, they are all linked to each other, once you start increasing one you start increasing the demand for others so it can get very complicated very quick. But I will just add that as a note, I think Mg and P are linked and should be fed in similar quantities to each other.
It's just something I will add to be aware of just in case one adds more phosphorous.

As pointed out there are so many reasons that plants will develop reddening.

Phosphorous should not be seen as the miracle fix. If a plant has lost all its roots and is growing stunted and red, that is to be expected because it lost all its roots.
You can't fix that by feeding it more. When an orchid has no roots it is even more sensitive so its a catch 22 situation and sometimes a weak orchid just cannot be saved. I also want to emphasize I believe in a balanced feed to avoid a deficiency occurring so that doesn't mean overloading it with phosphorous which orchids are in fact most sensitive to in too high quantities.

So yes it's a complicated matter if one looks in to it too much but the bottom line is just to avoid deficiencies in the first place. The best way is to start with a balanced feed, if a deficiency occurs then it is either because you are feeding too little or possibly because of micronutrients, if as a beginner one starts with a specialized formula then it is much harder to identify a problem.

Anyway I hope I have helped shed some light on the most important ones to be aware of:

calcium - shows up on new growth as black necrosis
magnesium- on lower leaves as mottles yellowing
phosphorous- darker older leaves, purpling, especailly on leaf undersides, stunted new growth (leaves grow smaller than previous leaves), eventually brown necrosis on older leaves
Iron- interveinal yellowing on new leaves.

As a last ps: one should confirm ones theory! Like I tried magnesium and I still honestly believe magnesium did not solve the problem I was seeing but phosphorous has. I will have to carry on evaluating and like mentioned I think it might be important to keep phosphorous and magnesium in similar levels.
The most markable effect I have seen which lines up with the theory is dramatic increased root growth. Phosphorous is needed for root development and even though I was very happy with my root growth if your plants are deficient in P, then applying a higher ratio of P to the other Nutrients should result in increased root growth!
If after applying more P you do not see improved root growth within one month then the orchid was most likely not suffering from a phosphorous deficiency.

This orchid for example started growing new roots from a root that had stopped growing:



I will make a seperate post on what supplements I use one day. Now that is when it gets complicated.
What is good value for money? microzial fungi, beneficial bacteria, humic and fulci acid, silicon supplements, seaweed extract and kelp additives, vitamins, root boosters or are they all snake oil?

I think some of them do deserve some consideration but the most important is the main "essential" nutrients.

If the plant is lacking any of these then adding those will be far more beneficial than any of the "boosters" one can buy. The main reason that nutrients get locked out is when the ph is not in the right range. So making sure the ph stays in the optimal level in the pot is the most valuable step imo but I will make a seperate post on my thoughts on which ones I think are good to add another day.

Last edited by Shadeflower; 11-14-2021 at 04:32 PM..
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Old 11-14-2021, 06:30 PM
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Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous
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Hey shade.
You also an under lights grower?

After looking at your photos you seem to have had almost exactly the same problems I had this year. Thrips invasion.

Thrips have been attacking young growths and roots, botrytis moving into the wounds(usually at the tips of the leaves), and the plants looking purple in the most peculiar way. Flush after flush of roots dead ending after an inch of expansion.

Many plants had so much anthocyanin production they were 80% purple. Some were turning yellow under light that was just fine months ago. Like a person losing their blood to a vampire and turning white. I found a ton of drowned thrips in my Nepenthes traps. And I got an awful realiztion about how many must be in my growing space.

After consulting with my orchid society, I nuked the entire collection with 2 spray and drench application Orthene for the first time ever.

The root growth has resumed across the collection after 2 weeks. The red rash of anthocyanin has greatly reduced. The yellow plants are now returning to a happy green yellow.

Mites can turns plants an ugly red as well. Very high light as noted.

But thrips are truly the devil. They bite, wound, infect and allow nasty secondary fungal infections to breach well grown plants...and they can fly. And the first signs they may be active is a new leaf emerging with specks red.

In my collection

Cattleya, vanda and reed stem epidendrums get the red specks.

Paphs get brown leaf tips and the stems often have brown welling marks from where the have bitten.

Cymbidiums get a silvery stippling on ther leaves and their bulbs start to look awful scared brown. Spikes halt a week after emerging and fall of perhaps a month later.

Phals gets the "bullseye" look around the bites sites in their newly emerging foliage.

The damage is still fresh, I can post some photos if there is an interest.

I agree...imbalances can happen even without pest pressure. Yet if pests are the cause of the imbalance and you cant see them, its an awful riddle.

Did you drop some pesticide on the collection recently?

Glad things are looking up.
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Old 11-15-2021, 07:51 PM
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Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous
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Hi Shadeflower,

I use Better-Gro Better Orchid Bloom 11-35-15 once buds start to appear. before that i use MSU 13-3-15. on my phal (only one, purple flowers).

i hope you were able to see the buds photo (on the other thread)?

btw, about light: if a bunch of us used the same light measuring app no matter if its accurate/proper, used the same way it gives readings if we use the same app from the same distance we get a reading we can compare, see pic.

like this one: Plant Light Meter on the App Store

only one lamp/one bulb in use, see pics.
bulb is approx 16 inches from leaves.
for 2 prior seasons i kept it MUCH closer.

temps in 60s reaching max low 70s. sometimes 59 with 58% humidity. which is cooler than last two seasons by a few degrees.

Thank you!

Attached Thumbnails
Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous-21d3c9d3-d9e9-4209-ab3a-8353289ecb7c-jpg   Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous-5af0eb52-5847-452e-bd98-729295583e50-jpg   Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous-a0dcdd9f-d1b7-499d-8b05-be18ac3d38f2-jpg  

Last edited by tedro; 11-16-2021 at 02:02 AM..
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Old 11-16-2021, 01:05 AM
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Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous
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Good discussion. Nutrition can be difficult to get right because it often depends upon the medium, the watering schedule, the climate and what is being grown. I believe that is why different fertilizers work for different people. One of the books I had on houseplants mentioned that if leaves show purple in cooler temperatures, one should add Phosphorous. That has worked with most of my other plants but I have never been certain if that is true for orchids as well.

I do have two plants whose new leaves emerge reddish as a way to protect them from burning...the Theobroma does this in bright shade with no direct sun exposure and the cinnamon tree does this in full sun (which it prefers).

---------- Post added at 12:05 AM ---------- Previous post was at 12:00 AM ----------

If one grows a variety of plants, it is quite natural to have a variety of fertilizers and supplements. I had to buy Chelated iron recently for some of my plants.
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Old 11-16-2021, 08:25 AM
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Orchids appear to be very undemanding of nutrition. Part of that is simply due to their slow growth rate, relative to other plants.

For any plant to gain a pound, it only needs about 5 grams of fertilizer nutrients, and easily 90% of that is nitrogen. It probably takes years for a phal or paph to put on that much mass.

I just thought of something that drives that home with me: Consider the growth in a poinsettia cultivated for the retail market. They start out as an unrooted cutting in the spring and end up as a full plant in time for the Christmas Holidays. It is well-established in that industry that the plant will require 1/2 gram of nitrogen in that period. By comparison, most orchids add far less tissue over that same time period.
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Old 11-16-2021, 11:23 PM
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wow these have been some fantastic answers, thank you for your observations.
technical_support yes I agree thris are the devil. I mean at one point I counted over 30 infected plants in 2 weeks.
And they keep coming back. It's like they are super mario with 3 extra lives. You wonder how. Even after soaking the orchids for an hour. They still are able to come back.
I have just stuck to my routine and I have been writing down which ones I treat. That way I know which ones should theoretically be clear and which aren't. They seem to operate on a monthly basis. Ie you kill them all (some eggs must survive) and a month later you spot them again.

And then if you do not get rid of them asap they start hopping onto about 5 plants next to them and hide there for a month to repeat it all over.

So I still will stick to believing that thrips weakens them so much. They nibble on the roots mainly so the orchid is constantly wasting energy regrowing root tips. What does roots growing need, phosphorous, so with thrips they get more depleted than without thrips. Or it's unrelated but I have seen too much positive effect from adding a bit of phosphorous.

tedro, good to see you do use a bloom booster but like I warned you they are really powerful. If I had yours I would be adding 0.1 to 1 ml to 10 liters. That is to your regular feed, I personally wouldn't use the bloom booster by itself...

the aim imo over a year is to achieve a 1-1-1 ratio.

So with 11-35-15 and 13-3-15 one can see that that can be achieved easily using the 11-35-15 for 3 months and the 13-3-15 for 9 months of the year or both together in a 3 to 1 ratio (3 part grow to 1 part bloom) and overall that would work out the same as using a 1-1-1 feed all year.

I also discovered that root boosters are the same product as bloom boosters. Basically phosphorous and potassium in a higher ratio to nitrogen promoted rooting and flowering.
Nitrogen in a hgiher ratio encourages growth.

I think the thrips have made me paranoid about feeding them when it is important but maybe not as important as I am thinking.

Like I am worried that feeding more phosphorous without adding potassium might have started a potassium problem next. IF you increase the one, then the ratio to the other changes and if they were 4:1 before then changing the ratio changes the availability to the orchid.

Maybe that is why phosphorous is generally sold with potassium?

I'm glad I got some good feedback on this. I know I'm not the only one who would love to understand nutrients better but it is challenging. I feel I am 1/20th there lol.

Last edited by Shadeflower; 11-16-2021 at 11:47 PM..
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