I'm frequently heard to say…

…"I'll tell you what I don't know."  

Rationale?   
I can't ask you if I don't know.   It works like this:-

I can tell you that - I don't know if Turmeric is herbaceous, or perennial, or I've just missed a watering too many.  

We'll maybe find out.  It does seem that, unlike Ginger the old section dried and dies - BUT - we shall see, it's just been watered.