flower stalk, vigorous growth
蓊 centers on lush, vigorous plant growth, especially the thick stalk or stem of a flower that supports abundant blooming.
蓊 combines the plant radical 艹 with 翁, which likely contributes the sound オウ and may suggest a full, abundant quality, fitting the idea of vigorous growth.
The plant top 艹 sits above 翁, which looks like a full, rounded shape. Picture a thick flower stalk swelling with vigorous growth, ready to burst into bloom.
For オウ, imagine an old man (翁, おう) tending a garden where every flower stalk grows thick and strong: 翁 -> オウ, and his care makes the plants flourish.
overgrown; exuberant; lush