Do I need to feed a thornless blackberry bush?

Hi Lucy,
I never feed mine it is so vigerous (as you have found) however I garden on clay so if you have a hungry soil I would probably feed at berry set.

I don't want to put you off but the thornless one we had tasted nowhere near as good as the thorny wild one that grows over from some waste ground that borders our garden.

Feed it up to end of June but debatable as some say: "no later than end of July as late bursts of growth may cause new canes to be subject to winter damage due to vigor and late flourishes of growth, plus you get too much foliage."

It will fruit only on last year's canes, so over feeding usually will not benefit new cane, foliage growth as energy is going to flowers and berry formation. Some argue regular feeding for berries, I just give light feeds usually at this time!