Basic rules for trimming
For various reasons, we must trim plants from time to time. The reason may be to structure, to ramify, to reduce or even to increase fruit or flower production.
Whatever the reason, the best time to do so is between November and March, when the vegetation is resting. However, frosty periods should also be avoided. Light trimming can be done during Spring or Summer. For flowering bushes you should wait till the end of blossoming. For Spring flowering bushes, like currant plants, you run the risk of eliminating the buds if you trim before Winter. For Summer flowering bushes, you should do so before vegetation commences.
A clean cut is important and you should put a protective covering on the bigger cuts. For a clean cut, first saw underneath the branch and then above it. This avoids tearing the bark. Cut just above an eye, as the opening will heal easier (it being close to a flow of sap).
Use appropriate tools and sharp blades. You will avoid risks of plant disease if you follow these basic rules.