duckweed, mugwort
苹 centers on small, floating or low-growing plants: duckweed on water and mugwort on land. Both are common, unassuming plants often found in clusters.
苹 combines the plant radical 艹 with 平 (flat/even), likely suggesting a plant that spreads flatly, such as duckweed on water or low mugwort. The exact historical development is uncertain.
The grass top 艹 over 平 (flat) suggests a plant that grows flat and even: duckweed covering a pond or mugwort spreading low across the ground.
For ヘイ, picture a flat plain of duckweed stretching to the horizon, and say 'Hey!' to a friend across the water: Hey -> ヘイ.
apple (fruit)