The vegetable you are talking about is called tóng hāo, also called "Chrysanthemum morifolium".

Artemisia selengensis is Artemisia selengensis. Annual or biennial herb with alternate leaves, long pinnate leaves, yellow or white flowers, achene ribs, two or three feet high, and edible or medicinal stems and leaves when tender.

References:

Baidu encyclopedia-chrysanthemum

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