Phak Chi Farang — Saw-Tooth Coriander & Long Coriander / ผักชีฝรั่ง

Isaan and Northern Thai — more heavily used in these regions than Central or Southern; associated with Vietnamese-influenced dishes in the North

Saw-tooth coriander (phak chi farang, Eryngium foetidum, also called culantro or long coriander) is an entirely different plant from regular coriander (Coriandrum sativum) despite sharing the same volatile oil compound profile and aroma. It has long, serrated leaves with a stronger, more persistent coriander character that does not wilt as readily as regular coriander — making it the preferred garnish for long-cooked soups and dishes served at high heat. In Thai cooking, it is most commonly associated with Isaan and Northern Thai dishes, particularly pho-style noodle soups in the north, and with tom yum. It also appears in some Vietnamese-influenced Thai dishes as a crossover between culinary traditions.

• Ngò gai in Vietnamese cooking is the same herb in the same garnish role; in Latin American cooking, culantro (the same plant) appears in Puerto Rican sofrito and Colombian salsas.

Phak chi farang's robust, persistent coriander character provides a long-lingering herbal top note to noodle soups that regular coriander cannot maintain — it is the difference between a herb garnish that is alive at the table versus one that has collapsed by the time the bowl reaches the diner.