Nutrients Availability in Nature

[kcpi3141]

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

[estación seca]

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.

[Ray]

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.

[kcpi3141]

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)?

[Ray]

Originally Posted by kcpi3141

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.

[thefish1337]

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,

[kcpi3141]

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.

---------- Post added at 11:46 PM ---------- Previous post was at 11:44 PM ----------

Originally Posted by thefish1337

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,

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

[thefish1337]

Originally Posted by kcpi3141

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.

yes.

[Orchidtinkerer]

Originally Posted by kcpi3141

as rainwater has very little dissolved salts

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.

[Ray]

Originally Posted by kcpi3141

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.

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.

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

Read THIS to start.

Originally Posted by Orchidtinkerer

TRainwater 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.

Well-stated!