回香 (huí xiāng) Fennel (Foeniculum vulgare)
回香子 or 回香籽 (both - huí xiāng zǐ), Fennel seeds have been available here for longer than I’ve known them. They are one of the more common seeds in five spice and other powder mixes, so they are easily obtainable. In fact, most people don’t even bother saying or writing the final character meaning ‘seed’; it’s taken for granted.
However until very recently (by which I mean about two weeks ago) fennel bulbs (回香头 - huí xiāng tóu) or fennel leaf/fronds (回香菜 - huí xiāng cài) were totally unknown. Suddenly they popped up all over my food delivery app. I still haven’t seen them in any store or market.
Seeds are around $2 USD for 100 g; leaves are 70 cents for the same amount; whereas the bulbs $1.40 for 300 g. The bulbs are still the most difficult to find.