What kind of pruning is best done in fall?
Prune only very late-flowering shrubs, such as Abelia (glossy abelia), Callicarpa (beautyberry), Hibiscus (rose-of-Sharon) and Clethra (summersweet) at this time. Prune rambler roses and remove all dead or diseased canes. Of course, it is always advisable to prune diseased and dead branches at any time of the year.
Fall pruning is not recommended for most deciduous trees, as it is best to wait until well into the dormant season before pruning. In general, on early and spring flowering shrubs it is advisable to prune just after they have flowered in late spring to early summer. On shrubs that bloom late in the season, it is advisable to prune them down hard in the early spring, before growth begins.
Courtesy of the NYBG Plant Information Service