kind of bean with flat pods
藊 refers to a specific kind of bean with flat pods. Its meaning is narrow and botanical, without broader abstract extensions.
藊 combines 艹 (plant) with 扁, which likely contributes the sound. The character was created to name a specific bean plant.
The top 艹 shows it's a plant, and the bottom 扁 suggests flatness. Picture a plant with flat bean pods hanging from it.
For ヘン, imagine a hen pecking at flat bean pods: hen -> ヘン, and the hen is eating the beans from the plant.