rue, herb used keep insects away
蕓 centers on a specific herbaceous plant: rue, an aromatic herb traditionally used to repel insects.
蕓 combines the plant radical 艹 with 雲 (cloud), likely as a phono-semantic compound where 雲 contributes the sound ウン and the plant radical indicates an herb.
The grass radical 艹 sits above 雲 (cloud). Imagine a cloud of rue-scented vapor rising from the herb to keep insects away.
For ウン, picture a rue plant releasing a cloud of scent that makes insects say 'un-un' (うんうん) in discomfort: ウン is the sound of rue working.
rape (seed oil plant, Brassica campestris); Chinese colza; yuntai