flower stalk; peduncle
Refers to the elongated stem that bears flowers, especially in vegetables like cabbage, radish, or rapeseed. Often used in the idiom 薹が立つ (tō ga tatsu), meaning the plant has bolted and become too tough to eat.
Once the rapeseed plant's flower stalk bolts, it's no longer edible.
This radish has bolted and become fibrous.