Similar plot to Day of the Triffids (1963)
One of the most interesting aspects of the episode is the showing of what would happen if Steed had to fight Mrs. Peel.
Plot is essentially a mash-up of Invasion of the Body Snatchers (1956) with Little Shop of Horrors (1960).
A decade later, Man-Eater of Surrey Green (1965) helped to inspire the Doctor Who (1963) Season 13 serial The Seeds of Doom: Part One (1976). The writer of that six-part story, Robert Banks Stewart, also wrote two stories for Series Four of The Avengers (1961) although neither one was "Man-Eater of Surrey Green."