[Can it be smoked?] No.
[A tobacco plant?] No.

Pineapplweed

Growing on the Earth, not extinct, not fictional (though that should be Abstract).
[Juxt] - Apology accepted, but you could have answered the outstanding questions at the same time.

Haste prevented me at the time. I have a terrible habit of remembering things only when I have no ability to address them.
[Is any part of it edible?] No.
[Should we be paying attention to your aproposeses?] I have attempted to relate accurately the reactions of the audience.
[Does it "eat" insects?] No.
[A dicotyledonous plant?] Unknown.
[Pineappleweed?] No.
[Is it a real, currently living plant?] No. As to category, I took my cue from Irach's latest outing - Fictional human, categorized simply as "Animal".

Vegetable. Alive by certain definitions, inedible, a specific plant, not found in the UK, not an individual plant, not a cactus, not an ancient tree, not found in Africa, not mainly found in the tropics, not aquatic, possibly an emblem, not a bush or shrub, not a thistle, not a type of grass, not known for it's flowers, definitely nasty, has leaves, cannot be smoked, not insectivorous, possibly a dicot, possibly seed-bearing, not a real, currently living plant, starts with P.
Not: wood, cucumber, a tree stump, bail, a wicket, kelp, poison ivy, primrose, pomegranate, a palm tree, pipe-weed, pinappleweed.

Thanks for the summary
Hmm, irach got a bit of criticism for his categorisation at the time. But, then I don't claim to set the rules for this game.

But obviously isn't, i.e. I'm stuck.

Was this plant invented by JK Rowling?

[Found on earth?] No.
[ptrifid] Pno.
[Potter-ed plant?] No.

I have a horrible feeling that I'm not going to have heard of this one.