Trim them now to keep them healthy and encourage new growth
Blackcurrants and redcurrants can both be pruned in winter, but they need a slightly different pruning method to keep them healthy and fruiting.
Blackcurrants grow as a stooled bush, with all the growth coming from ground level or below and they fruit on the previous season’s growth. The aim when pruning is to cut out as much of the old wood as possible and leave the new growth to fruit this summer. However, this isn’t always possible, because as you cut out the old wood, you also take some of the new shoots with it. To minimise this, always try and prune out branches low down to encourage strong replacement growth from the base of the plant.
Red and white currants are pruned differently because you want to maintain a framework of older branches from which new growth is made. Once a framework is established the new stems can be shortened back to between 7.5-10cm (3-4in) to create fruiting spurs, which will flower and fruit this summer. During the winter you can also thin out some of the older wood if the plant is getting too large and woody. This encourages new replacement growth and keeps the bush healthy.