overgrown, grow thick, be luxuriant
茂 centers on abundant, thick growth: plants that are overgrown, lush, or luxuriant. The idea extends naturally to anything that flourishes densely.
茂 combines 艹 (grass) with 戊, which likely contributes the sound and may have originally depicted a halberd or weapon. The compound suggests thick, flourishing vegetation.
Grass 艹 covers the ground so thickly that it looks like a dense, overgrown field. The lower part 戊 resembles a thicket of stalks, reinforcing the idea of lush growth.
For モ, imagine a mower struggling to cut through the overgrown grass: mow -> モ, and the thick growth resists the blade.
to grow thickly; to be in full leaf; to be rampant; to luxuriate; to be luxurious
thicket; bush; coppice; brushwood
to grow thickly; to be overgrown; to thrive; to grow in abundance
flourishing (of plants); thriving; luxuriant growth; growing lushly; rankness (of weeds)
growing thick
luxuriant (dense) forest
Kamo eggplant (Solanum melongena; round variety originally grown in Kyoto)
abatis