Seasonal timing in general terms only. No hardiness zone, no week-of-the-year for a species the essays do not time, and no contradiction of the larch warning.
NC State’s container chapter says repotting is best done in early spring, before plants start actively growing. That sentence is about container plants as a class. It is a reason to prefer the start of growth over the middle of summer. It is not a claim that every bonsai species, in every climate, is safe on the same morning.
The Piedmont Bonsai Club is more local, and it says so: in their area, repot in early to mid-spring, and stop when the first sustained heat arrives (they name the first 80-degree days in May). Mid-fall repotting is something some members do, and they call it riskier because of early cold snaps. On pruning they are explicit that there is no one time for every species, and they point readers to a horticultural guide for the Southeast. Generally, they say, major branch pruning is done in spring in the same period as repotting, finer shoots from spring through summer with exceptions, and it is a poor idea to prune after cool weather begins in fall if that pushes soft growth into frost. Some trees, they say, should be pruned only when fully dormant, in mid- or late winter. They also say not to prune in drought or in very high temperatures.
The dates in the essays are about particular trees, and they stay binding for those stories:
- Larch, on the raft page: very flexible, and unforgiving if repotted once the buds burst, or disturbed once in leaf. He bare-rooted that tree in winter. Wire on the growing tree cut in after six to eight weeks.
- The quarry larch, on the intermediate page: wire might need to come off in 6 to 8 weeks in the growing season, cut off rather than unwound, because the branches and trunks swell.
- The yew: eighteen months untouched, then a reduction; six months later the centre carved; the following spring a bare-root into the pot; one year in that pot before the last reduction. That sequence is the case study, not a yew calendar for other climates.
- He also notes that larch, though cone-bearing, is deciduous, so the winter image is a different tree from the summer one, with yellow autumn colour. That is an observation about the species’ habit, not a frost date.
If a club tip and one of his sentences seem to pull apart, follow his sentence for his tree. “Early spring, before growth” and “not once larch buds have burst” can both be true: the second is the line he drew for larch. A tree in leaf, a tree in drought, and a tree about to meet frost are the moments these sources tell you to leave the tools alone.