We took it outside today - it was getting very, very tall again.
I loosened its soil, tossed out some of the hard stuff, the old wood chips and gave it a top-up.
Lopped off the top of the old girl and planted to stubs at her foot.
She is now back in the lobby.
BTW - I don't really like dieffenbachia - we got this thing when it was about a foot and a half tall. We cultivated it just cause it was 'there', y'know?
It's not that it looks bad - they look pretty good actually. But it's hard to know where to put them - they're poisonous if kids touch 'em, cats touch 'em.
In my opinion, they belong in the jungle.