種
たね · tane · JLPT N3 · noun
seed
🌱 種 = 禾 grain + 重 heavy: the plumpest grain is saved as seed
Tane sounds a bit like tiny, and a seed is a tiny start. It also means the source of something: 話の種 is a topic of conversation, and 手品の種 is the secret behind a magic trick.
しゅ · shu · JLPT N1 · noun
seed
🌱 禾 grain + 重 sound hint: grain saved to sow, seeds come in many varieties
The on-reading shu also appears in 種類 (shurui), meaning kind or variety. Seeds sown from one plant type form a variety, so both senses share one root.