I have three vines in my greenhouse and I get a lot of growth in the spring-summer. although I get a good crop of grapes should I cut back this green growth as I do with tomatoes. ie side shoots, to get a better crop?
Grapevines produce excessive shoot growth and will easily fill a greenhouse if not pinched out. Remove unwanted shoots, leaving enough shoots with flower bunches on them to give a crop, and shorten these shoots back.