The only time that I would avoid pruning the tree is in Autumn.
Jul 16, SERIES 16 Episode 23 Winter is the best time to prune deciduous fruit trees such as apples, pears and plums. These trees will fruit well whether or not they are pruned. But if the trees grow too tall the fruit is high and hard to reach, and when there is. Jul 12, Summer Pruning Plum Trees. Thinning fruits can be regarded as the first stage of pruning, as it reduces strain on the branches.
Do this in early summer while fruits are still small and can be pinched out with your thumb and forefinger. July and August is the best time to prune plums in most Northern Hemisphere locations.