Posted: 14/08/2017 at 09:55
I'd cut the flower spikes off to stop it setting seed and put all its energy into the bulb for next year,
I would lift it once the leaves start dying back and plant in a pot for next year as they like restricted roots to make them flower, otherwise you get a lovely healthy plant, but no flowers.
you need to be able to just get your fingers between the bulb and the inside of the pot- any more of a gap and it will probably not flower next year (there is a good chance it won't anyway, they can be a bit finicky when they want) - planting mixture should be sandy/gravelly as they love good drainage.
as for hardiness it depends on the type of agapanthus you got, some are as hardy as you can get, some don't like frost, best bet is to google the name and it'll tell you how hardy it is.