Story, first published: Astounding Science Fiction, Jan. 1944
A very amusing adventure in which intelligent plants contrive to take over Earth by making men forget everything but listening to their music. The planet is a botanical grotesquerie: rifle trees that shoot pellets; vines that release lightning bolts; symbiotic blanket plants that can cuddle around bodies, supply food and medical attention, and even share intelligence and emotions; and the Encyclopedia, an immortal plant that can suck data from minds and from humans the knowledge of technology that intelligent plants are searching for.
In "Ogre" the traders own a female robot, Nellie, a nagging cost-conscious bookkeeper robot (who speaks very ungrammatical English - would she be programmed so poorly?) who, despite being a pain in the neck, always turns up in the nick of time to save the traders' hides.
Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.30