シュ, たね, ぐさ, おい, くさ, た, ほ
species, kind, class, variety, seed
JLPT3 G4 S14 F461
As per 重# (run through) + 禾 grain/rice → run seeds/saplings through soil in planting → *seed* → *type*; *kind*; *sort*; *species* (← seed as the type of the plant it will become) → *cause*; *source*. Other extended meanings include (source) *material*, *ingredients*, *breed*, *topic* and (magician's) *trick*.
[Full Kanji Etymology List]