There are two ways of pruning raspberries. Varieties include both summer fruiting and autumn fruiting raspberries.
If you are picking raspberries in July and August then you have a summer fruiting variety. If your raspberries ripen in September and October then your raspberries are autumn fruiting ones.
Pruning Summer Fruiting Raspberries
These fruit best on one year old canes, so cut out most of the old canes in autumn. These are the ones that have produced fruit this year. Leave the new canes that have not borne fruit this year.
Pruning Autumn Fruiting Raspberries
Autumn fruiting varieties of raspberry bear fruit on this year’s canes.
In January cut down all the canes you can see, every one. This may seem drastic, but these raspberries grow up from the ground to five feet high in one year. It is the new canes that carry fruit.
You do not need to worry about propagating autumn fruiting raspberries. They do a good job of that themselves, spreading like weeds throughout your soft fruit bed. It is best to grow them separately from blackcurrants and redcurrants to prevent them taking over.
All of your cuttings can be composted safely.
Can I leave the cuttings of the raspberry stems as a horizontal composting layer on the ground near the raspberries?
It’s not advisable for two reasons.1) The cuttings could spread disease. 2) Raspberries will spread underground and throw up new shoots like weeds anyway.
You can stick them upright in the ground and let them root if you want more raspberry plants.