medicinal herb
蓯 refers to a medicinal herb, specifically a plant used in traditional remedies. Its meaning is narrow and botanical, with no common abstract extensions.
蓯 combines the grass radical 艹 with 從, which likely provides the sound. It is a phono-semantic compound for a plant name.
The grass top 艹 signals a plant, and the bottom 從 looks like a person following a path. Imagine following a path through tall grass to find this medicinal herb.
For ソウ, picture sowing seeds of this medicinal herb in a garden: sow -> ソウ, and the grass grows.