Micronutrients? S.T.E.M. by Peters and Microplex by Miller
 

I stumbled upon this video of Alan Koch talking about fertilizers on Instagram. It is short, less than a minute, and he basically says:

- He fertilizes at full strength for 4 weeks and leaches with clean water on the fifth week. (Unclear if the clean water is still hard or not).

- Says most people don't know that epiphytes need more micronutrients than macronutrients, so he's adamant about adding STEM from Peters or Microplex from Miller.

I tried to find information on this micronutrient vs. macro on epiphytes, as I also wondered if it applied to other non-orchid epiphytic plants. But I couldn't find anything.

Here's the analysis of both products:

STEM

Sulfur(S) - 13%
Boron(B) - 1.35%
Copper(Cu) - 2.3%
Iron(Fe) - 7.5%
Manganese(Mn) - 8.0%
Molybdenum(Mo) - 0.04%
Zinc(Zn) - 4.5%

Microplex

Magnesium 5.43%
Boron 0.50%
Cobalt 0.05%
Copper 1.50%
Iron 4.00%
Manganese 4.00%
Molybdenum 0.10%
Zinc 1.50%

I wonder if the forum has any opinions to share and if there's a general feeling that it'd be helpful to pump micronutrients in a regular fertilizing routine.

I have a great deal of respect for Alan Koch as a grower - he and I seem to be cut from the same “better living through chemistry” cloth - but “epiphytes need more micronutrients than macronutrients“ is not entirely correct.

If you do dry tissue analysis of wild-collected epiphytes, you’ll find them to be about 90-95 % C, O, H, & N, with the majority of the balance being P, K, Ca, Mg, & S, with that last fraction of a percent being the trace elements.

If you look at the chemical processes going on within a plant, those in that largest fraction are actually consumed, meaning taken up and permanently incorporated in tissue so require replacement, while much of the remaining mineral mass consists of “transient” ingredients, meaning either they act as catalysts or “transfer agents” during the action of those biological processes and can be passed onto the next round of reactions, the ones after that, and so on.

Having said that, unlike the macros, the trace elements are prone to degradation by UV, so maybe the intended message is that the available supply - occurring on the surfaces of host trees - needs to be enhanced because it will be degraded by sunlight, something that doesn’t happen sub-surface soil to affect terrestrials.

If you use a quality, complete fertilizer, such as the MSU variants, K-Lite, etc., trace elements are included and needn’t be considered further.

I used to sell such trace-element products, but discontinued when I learned how easy it is to screw up a plant by overdosing them, or at a minimum, throwing them out of balance.

Don’t forget why STEM products exist: Pound-for-pound, trace element minerals are far more costly than are the macros, so it was common for large-scale nurseries to only apply cheap NPK fertilizers through most of the growth cycle, hitting them only once with the STEM.

Well that explains why "Norman's Optimal Orchid Nutrients" is basically an NPK fertilizer that doesn't contain any calcium and a mere 0.5% Mg.

As for Alan Koch, I think this is the classic example of how cultural notes vary from the large-scale greenhouse nursery to the home grower. He might've meant to say that orchids and other epiphytes need to be provided with more micronutrients through watering by the grower than terrestrial plants do.

I can see how the casual home grower using Miracle Gro (or Norman's) might lack Mg and Ca unless their water already provides it. Still, the hobbyist will more likely have a complete fertilizer like the ones you mentioned or even Dyna Gro.

Calcium and magnesium can have solubility issues when mixed with NPK fertilizers. This is why they tend not to be added to general fertilizers in larger amounts. Many people use NPK and Cal-Mag preparations in some kind of regular rotation, rather than mixing them at the same time. The trace elements are usually in the NPK.