Is this true?
 

I have some orchids sharing a basket, Neof. and Encycl., and I found this on orchideria.com "Some plants produce a chemical reaction in their fragrance that is a clear sign that nothing should even try to live near it. This aromatic battle is called allelopathy. This is also why not all orchids make the perfect pair when mounting together. Some might send out signals that they prefer to be alone."

Is this real and are there resources to find which orchids do well living on the same mount?

I haven't heard of orchids doing this.

After a quick Google search using alleopathy orchids I found a study via researchgate.net
I read the summary of a study of preliminary research into this written in 2014.
I did download the full study but it was written in Cyrillic.
From the summary it seems this result was seen in the protocorms and seedlings with in one case mentioned had "massive blackening and death during joint cultivation"
Also mentioned a few pairs that worked well together and others that did not.

Generally speaking, it is better to grow individual plants separately, if for no reason than to reduce the chance of pathogen sharing.

I thought "scent" was meant to attract pollinators, not to scare something away.

Orchids (likely all plants) contain phenolic glycosides. When tissue is damaged, bacteria can oxidize them into active chemicals that may smell or taste bad to the attacker, thereby providing some defense from further attack.

There has been some thought that such chemicals can fend off the root systems of plants growing too closely, and that may be why activated charcoal is added to the agar-based media in flasks.

Interesting points, especially regarding the charcoal.
I have occasionally wondered if having charcoal in the pot would reduce the amount of fertilizer the plants get.

Unlike the stuff used in flasking, the charcoal used in potting media isn’t “activated” charcoal, so it’s absorption is similar to some bark products.

Thanks that clears that thought up!

If you find only one study on this, it may or may not be true of orchids. There are a few plants that are known to use chemicals to eliminate the competition...black walnut trees are famous for it, for example, but it is not a very common ploy. Plants tend to eliminate competition by either growing quickly and having a dense canopy or just crowding out other plants with offsets, speedy, effusive propagation, roots or leaves.

One orchid crowding out the other would be a good reason to give orchids space when mounting or potting them.

Yeah, the whole article sounded... mmm... fake and dumb to me. I have a B. Sci. in biology but I'm no botanist so when it comes to plants I can be fooled. To me allelopathy is when two genetic characteristics (the alleles) combine to produce a fatal or harmful developmental disorder. My concentration was marine biology but I never studied phycology in depth. Oh and when I'm not in a classroom or a lab I will oversimplify because most people I know aren't biologists, although maybe here on orchidboard I should go ahead and split sugar production from carbon fixation instead of lumping processes not involving photons under photosynthesis but usually I just lose people if I get that detailed, and I'm not a botanist either so I'm a bit rusty (to put it mildly) on plant respiration and metabolism. Maybe I'm just too long-winded as well, I'm sure I've lost most of you by now ;)

I'm with you, it seems dubious. I would need a real study to believe it.

That said, allelopathy is very much a real thing. It is usually a plant somehow altering the soil around it so other plants can't grow. In the case of the western US we have a problem with invasive salt cedars filling their leaves with salt and dropping them, effectively salting the earth around themselves. The result is huge areas of river basin where nothing but salt cedars grow. In this case it's very destructive but still, Its really interesting to learn how that stuff works.

I am doubtful that fragrance or other gaseous chemicals can have such a dramatic effect in the environment around a plant, but I have learned many stranger things studying plants so I'm totally open to being proven wrong...

I'm not sure why people make stuff up about orchids, they are stranger than fiction!

Getting back to the root of your concern, I really think your basket with two species will be completely fine. Please post a photo sometime!

Most people here have heard about C3 and C4 metabolism. Many epiphytic orchids use C4.

That statement could be true. The word 'fragrance' could be a misinterpretation of terms used in scientific literature. I did my PhD on how plants defend themselves against pests/pathogen and sent signals to other plants via the emission of volatile organic compounds, and these are colloquially referred to as 'plant odors'. So I can see how this could be translated to 'fragrance' by a non scientist, and the entire premise of the statement could very well be true.

Also... I found the article in question, and when those lines are taken in context of the rest of the paragraph (and entire article), I'm fairly certain that they are talking about orchid + mount when referring to 'perfect pair', and not a pair of orchids on a mount. And it's well known that trees will secrete unpleasant chemicals in their bark to keep other organisms away.
Best Wood for Mounting Orchids: What Works and What Doesn’t – Orchideria

I used some harsh language and I was the one who was wrong about allelopathy. I'm not trying to make excuses but there are some factors at play beyond my control. I've been having some cognitive difficulties after a third bout of covid, and when I have covid I suffer a fever bad enough to make me delirious and then I have brain fog and disturbed circadian rhythms for several days, followed by intermittent brain fog and fatigue for a week or two. While this is going on I'm also cranky as hell. I had a similar experience shortly before I got my degree when I broke my leg in several places from the ankle to the knee and underwent general anesthesia for surgical reconstruction of the tibia, fibula, and ankle bones. My ankle and leg healed perfectly but I suffered serious memory and emotional issues for some time afterwards (from the anesthesia or the opioids or a combination of both I still don't know) and probably lingering somewhat to this day.

My decision to start collecting my own orchids was an attempt to alleviate this suffering, handling my mom's orchids has been one of the few things that helps me relax and remember that life is still good no matter how dark things seem so I figured my own orchids would be even better. Now I'm a bit obsessed with them but I still get stressed out from time to time.

I looked up allelopathy and indeed it is when plants produce their own herbicides/repellents to stifle competition. The name made me think of a phenomenon touched on in genetics I in which a homozygous genotype for a trait causes severe to lethal defects while the heterozygous genotype has mild to no ill effect on development, and I don't actually even remember what that's called in Latin, just that it's a lethal cross in English. Things from my courses are kinda fuzzy and start coming back when I read tangential topics to the knowledge in question.

I'm gonna do my best to be nice and not throw around crap that I don't know what I'm talking about anymore. More listening and less bloviating unless the topic comes to marine life, then it'll be no holds barred, but I might (hopefully) be right a little more often. For a few days at least, though, I'm just going to stick to my own observations and questions on the orchids I'm caring for or advice on purchases I'm considering. Oh and kudos to posts I like, yeah, I'll do that, too.

I don't think you were being all that harsh. At least I didn't take it that way. I'm glad growing orchids is a good therapy for you too.

I'm not at all a scientist, but probably could have been, so I do understand the content of the subject mostly. That said, I agree with Louis W regarding your post. I didn't see anything harsh or rude. Carry on, friend.

Discussion is a good way of learning.

I am always doubtful about declarations of new discoveries when there are not enough trials (that follow the scientific method and eliminate other factors) to prove beyond doubt a 'conclusion. 'Science news' that is not peer reviewed or proved with other trials should be taken with a grain of salt.

It has been discovered that plants use chemicals to communicate, to deter pests, attract pollinators, and even to close parts of themselves around insects (CP's). A few have been observed to kill competitors with chemicals (nothing grows around them...consistently).

When it is beneficial to the plant to eliminate competition, there are more effective ways to do this...growing faster and putting out a thick canopy, quickly sending out plenty of offsets, seeds, root growth, having roots that drain and store all the possible water/nutrients, etc. Plants that are alone are more likely to be eaten by something (especially tender, young plants) so it is to their benefit to survival to use one of these other methods so that they are big enough to survive an attack when they are alone instead of wasting energy on chemical warfare.

FL Orchid Collector
I didn't read your comment as harsh. Just another way to look at the question.

I cannot see how the production of eentsy, weentsy, teeny, tiny chemicals is more wasteful than the production of chemicals for growth. More mass takes a lot more resources.

I would think that a tender, young plant would be more likely to use “chemical warfare” precisely because it is relatively unprotected by size.

I think the reason we do not see much of plants using chemicals to eliminate other plants is that plants do not find it as beneficial. It is more effective to grow and produce more mass (more leaves mean more photosynthesis, more plants mean a better chance of survival for the species when adversity strikes).

A good example is an organic vegetable garden or flower bed...and weeding. Or the attempt to remove difficult to eradicate invasive species. These are the wildly successful plants. They are successful not by killing their competition with chemicals but by explosive growth. It would be so much easier to eradicate these plants if they chose to kill their competition with chemicals. It is not very difficult to clear a forest or yard of young Black Walnut trees.

I think this is just why we do not see it as often.