variety of artemisia
蔯 refers to a specific variety of artemisia, a plant in the mugwort family. Its meaning is narrow and botanical, without broader abstract extensions.
蔯 is a phono-semantic compound: the grass radical 艹 indicates a plant, while 陳 likely contributes the sound. The exact historical development is uncertain.
The grass top 艹 signals a plant. The bottom 陳 looks like an old display or arrangement, so imagine an ancient herbalist displaying a special artemisia variety.
For チン, picture a chin-high patch of artemisia: chin -> チン, and the plant grows right up to your chin.