This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 茺 is uncertain. It visually combines the plant radical 艹 with 充, but the original semantic and phonetic roles are unclear.
The grass top 艹 over 充 suggests a plant, but its specific meaning is unknown. Picture a mysterious plant whose purpose is yet to be discovered.
For シュウ, imagine a shoe resting on a patch of grass: shoe -> シュウ, and the grass top 艹 reminds you of the plant connection.
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