Nutrients Availability in Nature
 

Hi everyone, I just have a question that has been on my mind for a while and hope that someone may have an answer to it:

All over the net, I keep reading guides on fertilizing orchids that always say something along the lines of "these plants get their nutrients from monkey poop and rotting crap" in the wild. While common sense tells me that that is true (as rainwater has very little dissolved salts), has anyone actually sampled and analyzed the water that flows down from trees that eventually make its way to the orchid's roots? Or from rocks for that matter, for lithophytes?

I am asking because due to limited time and energy, we tend to bomb our orchids with fertilizer once a week or every two weeks to get good growth, yet nature is still able to compete with us---sometimes even outdo us---with the purported bird feces. Factoring in the frequency of watering in nature, which could be more or less than our methods, who actually fertilizes more on average?

Additionally, just how readily available and common are these sources of nutrients? I mean just imagine monkeys coordinating who will poop on which orchid: "Bro c'mon, I told you 5 times since breakfast that it's your turn on that catasetum today. Now please excuse me, this cattleya here needs some attention."

If anyone knows any research done on this subject, please let me know! I had fun typing this haha.

Best,
Kev

Welcome to the Orchid Board!

Orchids in nature live with symbiotic fungi inside orchid tissues. It is easy to observe blue-green algae, also called cyanobacteria, growing with many orchids. Cyanobacteria are among the very few organisms that convert atmospheric nitrogen to something plants can use.

I'm haven't looked into studies of orchid symbiosis but I strongly suspect it provides nutrients to orchids.

Dust, monkey poop, bird crap, and the like do wash down out of the canopy every time it rains. So do host tree exudates. BUT... they are very dilute (<15-20 ppm total; almost all N), and very transient, being present only for the first few seconds at the start of the rainfall. Fortunately, velamen grabs and holds the nutrient ions strongly to prevent the heavy rains from washing them away.

And, as ES said, microbes in and around the plants supply nutrients, either directly or by decomposing accumulated detritus around the roots.

Lithophytes get very little nutrition directly from the rocks. Anything they do get is indirect, again, mostly via microbes.

If you’re willing to invest, Benzing’s Vascular Epiphytes is worth a read.

Thanks for your answers! Wow, Vascular Epiphytes is $80 something on Amazon.....would love to read it though.

Since the nutrients come so transiently, I would assume that it is not very good for our home-grown orchids to be surrounded by moist, nutrient-rich substrate for over half a week (aka growing in pots)?

No, not at all. The nutrition brought with the rains are extremely transient, but the water is not. The degree of wetness in such rainforests is astounding - orchids' velamen is almost always saturated.

The uptake of nutrition only happens in solution, and unless there are mycelia to "shoot" them into the roots, only happens when the root is in contact with the liquid.

The key is not drying the plants out, it's keeping the nutrient availability low by only using very dilute solutions - just like in the wild.

The missing piece of the equation is that orchids are highly evolved to support microbial friends living in their roots. Microbes help provide phosphate, nitrogen, calcium, and iron. These are well studied but the reality is probably there is more, beyond just simple nutrients. Whether they live on a tree or a rock they have bacteria and fungi digesting the substrate and delivering it to the plant in exchange for sugars/nutrients in addition to the wash down. These microbes also produce plant growth regulating substances as well which adds to the complexity,

Thank you for all your replies! I think I have an improved understanding of it now.

Another related question: Considering a mounted orchid then, I would assume that we would only need to add a very dilute amount of fertilizer for each watering right? Since the water will quickly evaporate and run off, it is rather useless to give them as much fertilizer relative to keeping them in pots.

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Are there any studies on the presence of microbial symbionts found in greenhouse-grown orchids, as opposed to ones found in the wild?

yes.

This is the part that is confusing you about the equation imo.

Rainwater has got little dissolved salts for most plants yes but orchids need 10 times less nutrients than the trees around them so what has very little nutrients for most plants is plenty for orchids.

That is to me the most crucial aspect and I know I can water my orchids with pure rainwater for up to 3 months without them needing any additional feed. I do feed on every watering but I know rainwater provides them with quite a bit already and my fertilizer just tops it up a bit.

Birds poop all over the place and trees grow up to 100 meters tall so any poop on the top branch will get washed down into every corner of the bottom of the tree.

Plenty of nutrients getting washed down constantly without every bird needing to coordinate where to poop next.

That to me is the simple part. Using tap water is where things get complicated and people tend to have problems although this is debatable and might depend on the quality of the tap water.

Mine is very hard, very alkaline and has an imbalance of nutrients. If I were to use tap water to flush my pots over time I would be flushing that imbalance through my pots which would cause more harm than just using rain water and not even worry about fertilizing,

To me causing an imbalance in the orchid pots is far worse than underfeeding them

This is my preference after years of growing experience - I blieve in feeding the right quantity consistently every time, not feeding too much or too little thus eliminating the need for frequent flushing.
Others like to feed hard and flush even harder. To me it's the wrong approach but not everyone does it like me.

Actually, it’s just the opposite.

A plant can only take up nutrients while they are in solution, and as you pointed out earlier, that will be the case longer for a plant in a pot with its roots surrounded by potting media.

Read THIS to start.

Well-stated!

i do this...but with alcohol and my body :rofl:

I completely understand your point and I was just joking around about animals coordinating lol. Nice anecdote about using rainwater; I will try to experiment with that too! But as I said in my original question, has anyone actually quantified and done a chemical analysis of the nutrient availability where these epiphytes live? We all tend to give these hand-wavy explanations about nutrients in nature, so it will be nice if we have some data to back it up.

Ray gave some numbers earlier (10-25 TDS and mostly N) which was helpful, but if anyone knows a bit more, please let me know as I’m pretty curious about this.

---------- Post added at 12:35 PM ---------- Previous post was at 12:28 PM ----------

Wow that is really cool, I’ll look into these more! Do you happen to know how are they made? Is it a collection of inactive spores or some enriched agar solution? Are these randomly grown and harvested, or are specific strains desired and cultivated? I’ll try to find some papers later, but if you know anything off the top of your head please let me know!

What is in it will depend on where the sample is taken, and it looks like I misremembered...

See the chart below, from Benzing. All measurements are in ppm. Some things to consider:

• Just because a mineral is not shown does not mean it was not present; it means it was not tested for.
• The quantities are suspect, as we have no idea how long after the rain started that they were measured. That is, how diluted were they?

They are fermented liquids.

Specific species are selected for their actions, secretions, and compatibility, then they are blended with water, a sugar source (often molasses), possibly kelp extracts and other proprietary ingredients, and left to ferment aerobically.

Once the populations have reached target levels, the blend is packaged, the equipment steam cleaned, and a new batch begun.

The thing is, what's on the label is not necessarily representative of what is in the bottle. It is a minimum, but not necessarily complete.

Each state has its own labeling regulations, but all require that the stuff stated on the label be guaranteed. The producer decides what he wants to test for and guarantee, and that's what's on the label - and it may vary from state to state, depending upon their individual requirements, and the producer's interest in divulging info.

For example, KelpMax states it contains "so many percent kelp extract", because that's all that is tested. There are dozens and dozens of nutrients, stimulants, and plant growth regulators, but nobody is going to spend the money to test for them for every batch.

Thanks for that chart! Just what I was looking for.

Just in case I misunderstand, “rain water” means water collected without it touching anything, “through fall” means it hit some leaves first, and “stem flow” means that which is collected flowing down from trees? Is that correct?

what is in the rainwater will give you a rough idea.
You can also do a search for past threads on Nutrients, this one comes to mind thinking about the most recent ones, it will give you a better understanding of what orchids need:

http://www.orchidboard.com/community...ight=nutrients

There is also a guide on the Nutrient found in the leaves of certain orchids:

https://staugorchidsociety.org/PDF/W...ckLockwood.pdf

That is correct.

Rick and I collaborated on the development of K-Lite.

The problem with tissue analysis is that it tells you what the plant has been exposed to, not what it truly needs. I argue, however, that if you consider the evolutionary "niche" status of wild orchids, they would have evolved to thrive with whatever they're getting in that location, so it's probably a better "guesstimate" for them than it would be in cultivated plants.

Plant exudates also supply nutrients to other plants lower in the canopy.

Most plants produce some version of extra-floral nectar as a way to excrete wastes. Orchid growers see this in our plants too (some people call this "happy sap"). In addition to sugars, that substance is rich in mineral nutrients, such as potassium.

Exactly!

Alan Koch (Gold Country Orchids) let me in on a little tip about adding iron sulfate to feedings when growing Brazilian laelias (OK, "cattleyas"). The soil in Brazil is so iron rich that the terrestrial plants all exude it.

Organisms in and around the roots, and breakdown of debris hanging around the roots area, as well as nutrients washed down to the roots area -------- provide elements for the orchid.

Even ants and other things forming nests in or near the roots ----- or the media - can get a nutrient source going.

But for bulking up ----- we know the sun and the light and CO2 is behind all that ----- for producing the 'food' - through the photosynthesis process.

And we know that most orchids in general aren't super fast growers like banana palms, papaya, sugar cane ---- and a whole bunch of other plants/trees.

As long as the orchid gets a bit of the required elements every once in a while, then they'll just keep growing nicely - provided we look after them adequately.