yam
蕷 refers to a yam, a starchy tuberous root vegetable.
蕷 is a phono-semantic compound: the grass radical 艹 indicates a plant, while 預 likely contributes the sound ヨ.
The grass radical 艹 on top tells you it's a plant, and the bottom 預 looks like a pile of yams stored in advance.
For ヨ, imagine a yam that looks like the letter 'Y' and tastes like 'yo'gurt: Y + yo -> ヨ.