stump, sprout
蘗 centers on what remains after cutting a plant: a stump, and the new life that emerges from it as a sprout. The two meanings are connected by the cycle of cutting and regrowth.
蘗 is a phono-semantic compound with 艹 (grass/plant) and 檗 (a type of tree, also used phonetically). The exact historical development of the stump/sprout meaning is uncertain, but the plant radical suggests a botanical origin.
The grass top 艹 sits above 檗, which contains 木 (tree). Picture a tree stump with grass sprouting from its top: the old stump and the new sprout together.
For ハク, imagine a gardener hacking at a stump, and a sprout appears: hack -> ハク, and the sprout grows back.