Black Jeeragam | Cumin Seeds Black plants are hardy annuals that grow from 20 to 60 cm (8 to 24 inches) in height. The branched stems bear fine, deeply divided leaves, and the plant has a developed taproot. The pale blue or white flowers have five petals, numerous stamens, and five or six elongated fused carpels. What is black cumin good for? The medicinal use of black cumin seeds in various traditional herbal systems is known for a wide range of ailments which include different airway disorders, pain such as chronic headache and back pain, diabetes, paralysis, infection, inflammation, hypertension, and digestive tract related problems.