deviding dofodills

[joeinni]

Can clumps of daffs be devided when in flower

[Clanad]

They can be, of course, but the bulbs receive most of their nourishment for next years growth when the flowers fade and the leaves yellow and die back. It's best to wait until the fall... late summer at the earliest. This applies to tulips as well...

[sarah_louise]

But oddly enough the opposite applies to snowdrops. They are best divided when in flower (in the green ).
i know you didn't ask that but it might come in handy !