12-1-2? Why not the oft-recommended "balanced" ratio that's so commonly advised? During the growing-season I definitely have higher N than P or K but your phos/potassium sound wayyy low, am very keen for any elaboration on this you could give! Strikes me as anomalous and I can't begin to guess why you'd want p&k so low..
When I give my fertilizer talk, I start with "Everything you know about fertilizer is wrong". In reality the 12-1-2 is closer to WHAT THE TREES ACTUALLY USE, than the ''traditional'' fertilizer formulations. In a traditional fertilizer, the P - phosphorous and the K- potassium are far higher than what the plants actually need. There is a lot of P and K that gets wasted, because the trees don't need that much.
By the way, my 12-1-2 has 14+ other macro and micro nutrients, all in the proportions the trees actually use.
Why are the many expert bonsai artists able to grow fine bonsai even though their fertilizers are ''wrong'' according to me? It is because they flush the trees with plain water between doses of fertilizer. This leaches out the excess, the balance is restored because the excess is leached away. Rain also leaches out excess nutrients. We water bonsai heavily, and this water, ''corrects'' for the really poor fertilizer formulations most people use. Responsible stewardship would say we should not waste nutrients. The P and K that leach out of our trees end up in our ground water and surface run off water, eventually polluting our local lakes and streams and ground water. Is the amount significant? Probably not, there are many, many bigger issues to worry about than the one or two pounds a year most bonsai hobby growers use each year.
All the references to back up this 12-1-2 statement are in the link at ''First Rays Orchid Supplies'' that I supplied you. Many of the articles are based on Michigan State University research, done for the commercial potted plant wholesale producers. Read through it, the articles by Jan Szyren and Rick Lockwood are good quick overviews for the hobby grower, with proper foot notes to the actual research. This is 20th & 21st Century science. A 10-10-10 fertilizer solution is 19th century science, and at least 160 years out of date.
Because we water often with water that has no fertilizer added to it, we can get away with 19th century formulations. Some can create champion masterpiece bonsai with 19th century fertilizer. But why not take advantage of the more recent information. Trust me, my formulation works. If I made money selling the stuff, I'd put more time into promoting the modern fertilizers, but the profit margin is not there, so I don't knock myself out trying to ''convert'' the experts to update the ''accepted best practices'' of the bonsai community. But I chip away at the edges, one little post on a chat forum at a time.
Re Orchids, thanks that is a great analogy and am about to go check out the url, I've noticed this myself in that orchids' fertilizers tend to be strong fertilizers and their pre-made mixes are typically devoid of fine particles (however, they're usually entirely water-holding ingredients, not dry-out-quickly ingredients like bonsai soils- I wonder if one is better, or if they're each ideal/optimal for their use-case? I guess I'd think that a rapidly dried-out soil like bonsai-mixes would encourage better root-growth (w/ corresponding plant growth) but maybe orchids like a more stable/homeostatic moisture level than the dry/soak/dry/soak of bonsai-watering.
Ah, - people pay me to teach them how to grow orchids. But you are looking at orchid media correctly. Most orchids common in cultivation are species, or hybrids descended from species that are epiphytes in nature. Yep, that Phalaenopsis you see for $20 at Home Depot is descended from orchids that grew in the Philippine rain forests. In nature, where it rains twice a day and humidity never drops below 80% they grow in trees, roots attached to tree bark, with no media other than a thin layer of moss and lichens that grow around their roots. Between the morning rain, and the 3 pm afternoon rain, the sun comes out and will bake the roots dry, but the dry spell is only a matter of hours, and then the afternoon rain, then a little more sun, then the heavy night time fog, morning rain and the cycle repeats.
Actually I don't view orchid fertilizers as being particularly ''strong'', but I do advocate a much more moderate to low concentration feeding regime for orchid growing than any of the books written before the year 2002. Modern science is slow to spread in the orchid community too.
In a flower pot, on a window sill, these coarse but water retentive chunks allow air to circulate around the roots, but hold enough water that most people don't have to water their orchids more than once every 5 days to once a week. The epiphytic nature of most orchids is the reason these coarse, chunky media work so well.
Bonsai are usually terrestrial trees, with much thinner roots, adapted to living in humus and soils. Whole different environment. But air and moisture are required. The finer particle sizes needed is because of the adaptations to terrestrial living.
