aff.

[Anne Chambers]

Thanks, Greg, for posting the explanation. I'm not trying to be smart or
picky but I suppose the purists would prefer that we thought of it as
short for affinis (Latin, affinis, -is, -e, related or similar to) since
it is used as part of a Latin plant name.
It's a very useful abbreviation in remote places when you find plants
and you don't have access to the literature or even when you get back
home and still can't decide on their exact identity!
--
Anne Chambers