Yonks ago, post-house viewing, we took a detour to a nursery in Ottershaw where we picked up two pots of agapanthus. One had a single skinny shoot, the second a chunky one. Both were placed outside our front door to bake in the sun by way of an experiment. The one with the chunky stem had to be taped as it grew and began to split. Five flower heads in one big bloom = mega-panthus. Brilliant.