Trachyspermum roxburghianum (also known as Carum roxburghianum) is a flowering plant in the family Apiaceae. It is grown extensively in South Asia, Southeast Asia, and Indonesia. Its aromatic dried fruits, like those of its close relative ajwain, are often used in Bengali cuisine but are rarely used in the rest of India. The fresh leaves are used as an herb in Thailand and it is used medicinally in Myanmar and Sri Lanka.
The small dried fruits, commonly referred to as seeds, are similar in appearance to those of ajwain, celery, and caraway. Because of their similarity in both appearance and flavor, it is often confused or substituted with celery seed.
Known as radhuni in Bengali (Bengali: রাধুনি), is often confused with celery and is known as wild celery in English. It is known as ajmod in Hindi (Hindi: अजमोद) and Urdu (Urdu: اجمود), both derived from Sanskrit ajamoda (Sanskrit: अजमोद) or ajamodika (Sanskrit: अजमोदिका), from which the name for ajwain is also derived. It is also known as kant-balu in Burmese, and phak chi lom in Thai (Thai: ผักชีล้อม), although this name may also refer to a variety of celery.
It is a very strong spice, with a characteristic smell similar to parsley and a taste similar to celery. A couple of pinches can easily overpower a curry. In Bengali cuisine the seeds are used whole, quickly fried in very hot oil until they crackle. They are sometimes part of a local panch phoron (Bengali five spice) mixture replacing black mustard seeds; the other ingredients are cumin seed, fenugreek seed, fennel seed, and kalonji (black caraway). In other places, a common use is in pickling or spice mixtures.