The beds and your gardens are perfection Arlene. Why would I expect anything else. Love the scarecrow figure at the side fence!

>> N-P-K as a group.

I'm trying to recall the terminology I heard 1-2 times that distniguished THREE groups:

micro-nutrients (trace amounts like Mn, Boron, Selenium, probably Cu)

macro-nutrients (the big three NPK, though no one mentions CO2, O2 and water as nutrients!

and the in-betweeners that are needed in moderate amounts: Fe, Mg, S, Ca ....

I think they had some tidy Greek or Latin prefix for "in-between", like "hemi". I forget which group Si fell into. Maybe it's a trace requirement for most plants, but a "hemi" for grasses and bamboo.

I have to admit that I am more the bohemian type gardener who clearly does not have the analytical nature to question in depth every aspect of everything that has worked for me for years. I wish I could blend in this conversation;...yet I will now bow out.

Its been interesting to me;... yet less than something I would be able to worry with.

Everyone is a geek of something or another. For me, it's plants.

I do think it is imperative though, that if one is writing an article that others may look at as "gospel" truth, the writer needs to base his concepts on more than just what he thinks, unless he presents his ideas as personal thoughts from the beginning.

I learned the essential nutrients as primary (N,P,,K), secondary (S,Ca,Mg) and trace nutrients (the rest). Or macro, intermediary and micro nutrients.

There certainly are instances where plants require selenium and/or silicon for health, but they are not part of the essential nutrients for all plants.

I like "primary, secondary and trace". I personally think of iron as being in the middle group, probably because I've seen iron deficiency (indoors) more often than anything else. Perhaps due to pH being wrong .

The three groups are categorized by the quantity of nutrient used.
The fact that iron deficiency is or is not fairly common has nothing to do with it.