Almost forgot to mention what Mr. Onishi said about fertilizing his stressed pine (see previous two posts).
“After a year of rest in which I didn’t pinch or prune, but during which I gradually gave it higher doses of fertilizer…” That’s it. Not too much to go on, so I’ll try to flesh it out.
Most bonsai books and teachers say to avoid fertilizing stressed trees until they show signs of recovery. This is pretty good advice, but still leaves a lot to the imagination.
Mostly, I use mild, slow release organic pellets. With ordinary stress (like from rootpruning), I start putting pellets on the soil about a week after transplanting. By the time the pellets start breaking down and leaching down to the roots, the tree is ready to receive the modest amounts of nutrients that a few pellets provide. After that, about once a week, I add a few more pellets so that a steady flow of nutrients is assured.
With severely stressed bonsai, I wait until I see signs of new, healthy growth before I start feeding.
More critical than how you feed a stressed bonsai, is how you water it. I suspect more stressed trees die from drowning than any from any other cause. It is essential to understand that stressed trees use much less water than healthy trees. So be careful, don’t love your sick bonsai to death by watering before it needs it. Wait until the soil is pretty dry (but not quite bone dry), before you water.