This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 芄 is uncertain. It visually combines 艹 (grass) and 丸 (round), but the original meaning and component relationship are unclear.
The grass top 艹 over a round shape 丸 might suggest a round plant or seed, but the actual meaning is unclear. Treat it as a rare character with an uncertain meaning.
For カン, imagine a can of grass seeds with a round 丸 shape on the label: can -> カン, and the grass top 艹 sits above the round can.