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.
Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous
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