they say to cut back in spring even though they are in bud, this puts all its energy into making more buds for following year, so even though you loose some this year , you will get many more next year, so i would say choose which parts to prune evenly, about half this year and another next so you dont loose all ya buds, if that makes sence,but you can prune whenever you like and can be cut back quite alot to, hope this helps