Good idea to pluck JBP needles in late winter?

Would needle thining in late winter stimulate candle formation?

I don’t know that thinning in late winter will stimulate much candle formation, but I recommend thinning now (or any time up until they start growing in spring) if the trees haven’t already been thinned.

No . Do not touch at this time of year, leave until after the candles have hardened off and then prune candles and thin needles.

@geoffm5eay - could you say more about why you’d avoid working on pines in winter?

You can wire and prune but that was not what the question was. But the answer to the question then is no it will not stimulate candle formation. Japanese Black Pines are multi flush pines, and are not treated the same as single flush pines.

Hi Chris
I often complete needle thinning in late winter early spring. This is part of balancing the energy to promote even growth, open areas to better ventilation and sunlight. Removing the extra needles does not in itself foster new buds or candle formation. However, the combined effect of reducing needles, wiring down the branch, opening up the area to increased light exposure and decandling does contribute to back budding.
Normally needle thinning can be completed in the fall but there is no harm In doing so late winter and early spring before decandling.
Like any bonsai technique it needs to be applied carefully with respect to the tree’s condition and stage of development. One of the reasons for delaying needle thinning until late winter, early spring is to ensure the tree remains healthy and robust throughout the winter season. Another reason is that in a JBP nursery like mine it is often difficult to complete all the fall maintenance routines during the fall. It is best to complete the needle thinning prior to decandling for the best effect to be gained from decandling. In my area this is prior to the beginning of June for trees in early stages of refinement and the beginning of July for those in later stages of refinement. The reason for the timing difference relates to the length of needles desired after decandling.
Needle thinning can refer to removal of upward needles, downward needles, last years needles, orsome of the needles on current developed candles. Each of these steps may be used to direct energy, promote bud and candle formation in desired areas. For example, removing needles from locations where buds are not desired, can increase the likelihood of buds/candles forming in areas where the needles have been left.
Hope this additional information helps! For additional resources check out the archives on Bonsai Tonight, lots of great detailed articles included.