Identify a story about plants mingling sexually with humans

Question

Published back during the unbridled excesses of the late 60’s or early 70's (definitely before 1972) there was a book I read in which some kind of climatic change caused sentient plants to overrun the Earth. It was quite a shocking find for a High School library of the time.

I believe it began in South America (there is an intense impression of green), and the only way mankind was able to reach an accommodation (and avoid extinction) was to join forms of sexual reproduction (putting it delicately). I’m sorry, but that is the most I remember; I think possibly I only skimmed it.

If someone has a suggestion where to look I would appreciate it: I do not want to unconsciously plagiarize original work.

It is not “Greener than you Think” ,“Day of the Tryfids”, “Midworld”, or “Vaster than Empires”.

Answer 1

It's not Earth, but this sounds like The Pollinators Of Eden by John Boyd. I read it in the early 70's

"This hybrid has enough Freudian fertilizer to swamp any Eden which in this case happens to be Flora, "the Planet of Flowers." Freda Caron's fiance, Paul, has been seduced by a garden of giant orchids on Flora so instead of returning to earth, he sends her some singing tulips for her experimentation as well as young Hal Polino. Originally frigid, Freda blossoms while tiptoeing through the tulips with Hal. Through circumstances too bizarre to go into, Freda ends up with an orchid on Flora, gets pregnant and gives birth to a little seedling. A sorry transplant indeed." -- Kirkus