Agapanthus Plant .

[Hazlinny]

Please can someone tell me should I cut down the long stem of the plant now that it has finished flowering?

[dannyk13]

http://fairweathers.co.uk/how-to-grow-agapanthus/

[Chipchopper]

Yes, definitely.
This will divert energy to be stored in the bulb, ready for next years growth, rather than it being channeled into seed production.

[Hazlinny]

Thank you both for your help and redirection to site.