Last Sat's Telegraph gardening section had an item on Agapanthus so as
there has been some interest in these magnificent plants recently(love
'em or hate 'em!) I thought I'd relay it for those who didn't see it.
In a nutshell; They need warm, sunny, well-drained soil.
Next years flowering buds start to develop about now, so they need
plenty of water (especially those in pots) and high potash feed NOW.
Interestingly it says that "Letting them seed does not seem to affect
flowering". I query that!

Pam in Bristol