Merchant NPCs sell ingredients growing on potted plants they own
The behaviour in question: if a merchant NPC own plants, the ingredients that grow on those plants are available for sale.
A good test case: infamous Helviane Desele sells corkbulb roots along with her moon sugar.
This needs vanilla testing since the data is so far contradictory. UESP NPC information pages suggest this is expected behaviour in at least some vanilla versions (http://en.uesp.net/wiki/Morrowind:Helviane_Desele). Andrei Kortunov, however, tested with the Russian version of Morrowind with Bloodmoon update and no third party patches and found that merchants do not sell the contents of organic containers there.
It needs more people with vanilla installations to test.
Even if this is confirmed to be different from the vanilla behaviour, I think it makes perfect sense that alchemists and apothecaries grow ingredients for sale, and I would like to see this behaviour at least optionally available.
#3 Updated by Daniil Baturin 7 days ago
I seriously wonder why UESP contradicts the vanilla behaviour in this case. It says that about many other NPCs as well, and that information was added before OpenMW project even started. Perhaps that was the original behaviour that was "fixed" in subsequent patches. Some other fixes do not feel right to me either, for example, removing the ability to steal from unconscious NPCs.