Yes, we’ve all done the Triffid jokes as kids when we’ve seen the signs, but why on earth is the word “plant” used to describe industrial buildings, vehicles etc?
My dictionary just says “special use of plant[sup]1[/sup]”, where sense 1 is the usual “green thing that grows in the ground” meaning, but gives no clue as to why. So what is the connection that I am not getting?
“O.E. plante “young tree or shrub, herb newly planted,” from L. planta “sprout, shoot, cutting,” perhaps from *plantare “to drive in with the feet, push into the ground with the feet,” from planta “sole of the foot,” from nasalized form of PIE *plat- “flat” (see place (n.)). Ger. Pflanze, Ir. cland, Welsh plant are from Latin. Broader sense of “any vegetable life” is first recorded 1551. The verb, “put in the ground to grow,” is O.E. plantian, from L. plantare, from planta. Most extended usages are from the verbal sense. Sense of a building “planted” or begun for an industrial process is first attested 1789. Slang meaning “a spy” is first recorded 1812. Planter “proprietor of a cultivated estate in W.Indies or southern colonies of N.America” is attested from 1647; hence planter’s punch (1924).”
So “plant” meaning a bunch of industrial buildings comes from the sense of the buildings being “planted” in the ground.
This obfuscates things for me, since the Irish and Welsh words mean “children,” creatures that (in my experience) are rather more likely to run around shrieking than to resemble plants or even heavy machinery.