Oil producing plants ravage the earth, killing humans with a lethal whipping sting. I re-read "Day of the Triffids" quite recently and it is a good book - easy to read, and fast-paced.
I don't think I saw the 1962 movie, but the 1981 Australian-made TV series was shown again last year, with all the episodes one after the other in a "Triffids Evening," and apart from the excruciating 1970s clothes, it was great entertainment. (The later film "Children of Men" seemed to me a poor rip-off of the Triffids plot.)
Now the BBC is to remake it into two feature-length episodes to be shown next year.