falling leaves and barks
蘀 centers on the natural process of plant material detaching and falling: leaves and bark dropping from trees.
蘀 combines 艹 (grass/plant) with 擇, which likely contributes the sound and relates to selecting or removing, suggesting plants shedding material.
The grass radical 艹 sits above 擇, like a hand selecting and pulling away dead leaves and bark from a plant.
For タク, imagine a tacky layer of fallen leaves and bark sticking to the ground: tacky -> タク.