Some guy from Iceland: Isint the red weed in The War Of The Worlds a part of a terraforming process instead of an sentient alien.
: Sentience isn't a requirement for qualification as a plant alien.
Hollow49: Yes, but the weed didn't do
anything - just grew and clogged up the Thames. It was a plant of alien origins, but I don't think it really counts as a Plant Alien
. The Triffids are the real trope-maker here, I think.
: Took out references to Swamp Thing and Dominion Tank Police because they're not aliens
. Also not sure about Jayce and the Wheeled Warriors.
Pteryx: I assume fungi also count in this trope (such as the mi-go from the Cthulhu Mythos)?
: Atack of the Killer Tomatoes isn't about aliens either.
I'd say that fungi count because regardless of any scientific classification, if you stopped a guy off the street and asked him if mushrooms are plants, he'd say "yes". And as for the question of sentience, I'd say that it isn't about sentience, but creatures
. A plant from another world that just grows and does nothing else shouldn't count.
In fact, we may be better off renaming the trope to Plant Creatures
. That way you can include Swamp Thing
and omit alien daisies that just sit there like real daisies.
This trope has bugged me for some time. Plants aren't called plants because of their chemical composition - it's because they're planted in one place, i.e. they don't move. Similarly, "animal" at least *sounds* like it should mean "moving" - which would include humans and robots too, but I don't mind that.
Maybe that's not how they're formally classified in biology, but Earth biological classifications shouldn't apply to aliens anyway. --Document N