This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 葈 is uncertain. It combines the grass radical 艹 with 枲, but the origin and original meaning are unclear.
The top 艹 suggests a plant, and the bottom 枲 looks like a tangled mass of threads or fibers. Picture a plant used for its fibrous stems, though its exact meaning is obscure.
For シ, imagine a single strand of fiber from this plant: the sound 'she' (シ) as you pull it free, like a whisper of thread.
cocklebur (Xanthium strumarium); cockleburr