Are there situations where there is an advantage to using chemical fertilisers for trees that are in development?
If you want to build the tree’s “immune system”, you must “feed” the microbial activity in the soil and this can only be done by using organic fertilizers. Inorganic fertilisers might offer faster results - during development - but at a cost - the tree is more vulnerable to pests and disease.
If I remember correctly, Ryan mentioned that they’re ok for foliar feeding for trees in development. Might be for deciduous only and maybe junipers too, not on pines.
Check the fertilizer stream.
As ever, start with the question “what am I trying to accomplish?”
I get most of my material from nurseries, and I’m cheap, so the first objective is usually development of a trunk. I like to get the tree into a bonsai soil and training (big) pot when I can, but in the mean time, I heap on the slow release chemicals. Nurserymen use these because they give fast growth.
Once refinement starts, and pot size reduces, every spec of growing space in the pot needs to be maximised, so organically all the way.
I agree with Andy. If you are looking to grow the tree/trunk/thicker branches. Fertilize, Fertilize, Fertilize. If you are looking for faster thick growth, your roots need to look like your branches so it should not be in bonsai soil. Put it in the ground or a grow box with some good shrub/tree soil. Bonsai soil does not promote the thicker roots needed for faster thick growth. Feed in the grow box/close to tree and that will encourage smaller roots to grow near the tree.
Use tree and shrub fertilizer. It is a more powerful mix.
Have fun.