As both conifers & deciduous trees shift from summer dormancy to a vascular growth cycle, there are lots of different types of work opportunities that one can consider in regard to working on your bonsai.
For conifers this can be cleaning out old/dead needles as well as cleaning up the shape (Scott’s, Mugo, Limber). It is also a perfect time to do major structural/bending on ALL our species as the coming vascular growth will heal most damage that might occur.
However, we do need to quantify for deciduous trees in that you cannot take off a heavy amount of foliage in the Fall. The trees use that foliage to set itself up for winter hardiness as well as setting itself up for growth next year. You need to leave them alone in regard to removing lots of foliage and wait until Spring. OR you can be careful and do this work only at the start of [or better] prior to the vascular growth. This timing would allow for a second and additional flush of growth for the year and more twigging – timing is more crucial.
Lots to do and discuss; BRING YOUR TREES, work and discuss together!
See Notes: Captured from Mirai Live-stream August 2017 Includes Q&A