How old are "trained gooseberries " ?
 

http://www.bbc.co.uk/gardening/today/index.shtml

Did a search on jobs, February, kitchen garden and it said

Gooseberries
Shorten sideshoots on trained gooseberries back to two or three buds.


My gooseberries were planted 3 years ago so this Summer would be the third
harvest. Do I need to shorten them and if not now, in how many years will I
have to start doing it?

Thanks in advance for your help.

Caroline