Not sure what type of vine you want to prune. Most vines can be cut back by two thirds or even to within one foot of the ground in early spring. In cold winter areas you do not want to be pruning vines as they are dormant and pruning could wake them up. Some vines like ivy are very tough and can be pruned any time of year. Perhaps you can send me a photo of the vine in question and also tell me where you live. Looking forward to helping you with more details with your question. Keep growing, Marianne Binetti