When I saw the title of this episode–“Monster Plant”–I was wondering if we’d get a taste of Biollante. More than a taste, as you can see from the still of people being attacked by whipping tentacles, and then particularly the image of a monstrous rose.
More than that, the film also prefigures Legion from the second Heisie Gamera film, as the Monster Plant flowers and threatens to unleash its spores over the city. One can only assume some of the shakers who made those much later films saw this show as a kid and it really lodged in their heads.