ive got one as well.book says prune out old and weak stems when flowering has finished
i sometimes cut out bits before in april and again after its flowered,but i keep mine short about 3or4 ft tall.

Hi Plantmaiden - so I cut off the stems that have just flowered and leave the new growth alone? I'm a bit dense about pruning as you can tell!

just give it a bit of a hair cut really and ya cut off the flowered stems so new growth will flower next year.
i prune to keep a nice neat shape or are you growing it as a 6ft bush.
i cut out some of the old longer stems lower down in the bush so its stays tight and bushy. hope that makes sense

Thanks Plantmaiden for the clarification! Will get out there and do my stuff tomorrow. I only planted it last year, it's about two foot by two foot now and flowered beautifully even though I did nothing to it after it finished flowering last year. I'd like it to get to around 3 ft x 3ft and then keep it that size.

Lovely Spirea Jan looks too vigourous for my garden. I have old Goldflames and I trim after flowering. There is no harm every now and again giving a No2 haircut prune+ water + cosset in the autumn. Fuss again in the spring and back again with a wonderful display.

Thanks for the advice Dorjac, I feel a bit more confident now about tackling it!