Does this need pruning like blackcurrants ? Or like gooseberries ?
Good question. I have jostaberry in 2 different areas and they behave differently! One seems to have more actual fruiting spurs than the others, on quite old wood, like a gooseberry would have. Others seem more blackcurrant like.
On the whole, jostaberries seem to not mind being right cut back when the stems get leggy, if you just have a look each year and take out the worst leggy stems, this will keep it in check. They do tend to be a bit vigorous after the second or third year! Some here just cut off the stems that get in the way, and they seem to do very well with their fruit.
Thanks for that. I suppose the good thing is that I can plant the cuttings and have more jostaberries ?
You certainly can! Or you can be lazy, like me and stick a whole bunch (dozens) of jostaberry sticks in a bucket of water in the autumn and forget about them. They sat in that water for at least 4 months through freezing temperatures, and every single one ended up with masses of roots. They are really tough ;D
Would it not be better to prune them as soon as they have fruited ?
You can prune them anytime really, they are so tough. I was just tidying mine up in the autumn. If you want lots of extra stems, prune early spring. You may get some stems growing if you prune after fruiting too.
Jostaberries fruit best on previous years wood - this declines after 2 years so cut out 3 year wood after harvesting. Maybe simpler to just cut out oldest 1/3 of the shoots after harvesting.