woody climbing plant
薢 refers to a woody climbing plant, a specific botanical term without broad abstract extensions.
薢 combines the grass radical 艹 with the phonetic component 解, suggesting a plant whose name sounded like 解 in old Chinese.
The grass radical 艹 on top of 解 (unravel, solve) suggests a plant that unravels or climbs like a vine, a woody climbing plant.
For カイ, picture a climbing plant growing over a dock (kai) by the water: dock -> カイ, and the vine covers it.
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