This is the first year I have grown dahlias and with much success; they look absolutely glorious and I feel if the weather is kind (I live in Norfolk), they may well flower through to November. My neighbour leaves hers in the ground over winter and just mulches which proves successful and I plan to do the same. My question is, once flowering is over, should I let the stems and leaves die back or do I cut them down. Furthermore, does the mulch have to be removed in the spring/early summer to allow for growth? thanks for your help.