Old English plante "young tree or shrub, herb newly planted, a shoot or strip recently sprouted from seed," from Latin planta "sprout, shoot, cutting" (source of Spanish planta, French plante), which is perhaps from an unattested verb *plantare "to drive in with the feet, push into the ground with the feet," or perhaps "to level the earth," from planta "sole of the foot," from nasalized form of PIE root *plat- "to spread." German Pflanz, Irish cland, Welsh plant also are from Latin.
Broader sense of "any small vegetable life, vegetation generally" (sometimes popularly excluding trees), "an individual living being with material organization but not animal in nature" is recorded by 1550s.
Most extended usages are from the verb, on the notion of "something planted;" such as "construction for an industrial process," 1789, at first with reference to the machinery, tools, apparatus, etc., later also the building; also slang meaning "a spy" (1812). Many of these follow similar developments in the French form of the word.
Old English plantian "put or set in the ground to grow" (transitive and intransitive), also "introduce and establish, set up for the first time," from Latin *plantare "to plant, drive in with the feet" (see plant (n.)). Reinforced by cognate Old French planter.
Without reference to growing, "to insert firmly," late 14c. Of colonies, "introduce and establish new settlers in," from c. 1300. Figuratively, of ideas, etc., from early 15c. Meaning "to station (someone) for a surreptitious or secret purpose" is by 1690s; sense of "place (something) in a concealed place to mislead a later discoverer" is by 1865. In pugilistic slang, "to land, deliver" (a blow, etc.) by 1808. Meaning "to bury" is U.S. slang from U.S., 1855. Related: Planted; planting.
"plant of the genus solanum," with white flowers and black poisonous berries, Middle English night-shade, from Old English nihtscada, literally "shade of night," perhaps in allusion to the berries; see night + shade (n.). A common Germanic compound, cognates: Dutch nachtschade, German Nachtschatten.
poisonous plant (also known as monkshood and wolfsbane), 1570s, from French aconit (16c.), from Latin aconitum, from Greek akoniton, which is of unknown origin.
The highly poisonous alkaloid in it, once isolated, was named aconitine (1826). The ancient folk-etymology of the name is Derived by the ancients from Greek akoniti "without dust," hence "without struggle or fight," hence "invincible" in its deadly effect. But Beekes finds this "hardly possible" and proposes a substrate origin.