How to split an agapanthus?

dodge.kt

We have a massive agapanthus in a flower bed.  It’s probably nearly 20 years old.  The question is can we split it easily and what is the best way to do it?  We cannot dig up the whole plant to split it because it is too big.  Also when is the best time to do this? Thanks 

Hostafan1

When it's dormant , in winter, you really have to dig it up to split it. It's easier , ie less difficult, than trying to do it in chunks.
Your only other option is to just leave it.