The soil under pine trees often becomes acidic from pine needles dropping and decaying into it. Grass seed prefers a neutral pH and won’t grow in high-acid soil.

"Epiphytes, amazing plants like moss and bromeliads found in trees, face growing threats." ScienceDaily. ScienceDaily, 12 October 2023. <www.sciencedaily.com / releases / 2023 / 10 / 231011182046 ...

The author notes that hydrangeas, which are perennial everywhere, are noted for being pink or red growing in alkaline soil such as our own, blue on acidic soil, and purple on “neutral to slightly” I ...