Not sure what you mean by "plumy," but it is possible it's deadly hemlock.

http://caltest.nbc.upenn.edu/poison/plants/pppoiso.htm

On Mon, 24 Nov 2003 18:03:21 GMT, "Broomhilda"
opined:

There is a shrub that grows at least from North Carolina to mid-Florida. It
grows 4-5 feet tall. Has plumy white flowers and is in bloom now. I know
this is a very brief description but I have not had a chance to see it up
close.

Someone in NC said it was Queen Anne's Lace but, although it may be a local
name for it, it is not what is commonly called Queen Anne's Lace. Queen
Anne's
ferny leaves, smells like a carrot when the stem is broken and is definitely
not a shrub.

Can anyone tell me what this particular shrub is?

Pixi