Basil (Ocimum basilicum) is an herb plant commonly grown on Earth that is added to food to improve flavor.
While living in the city of Chandigahr, Khan Noonien Singh lived in a home with a rooftop terrace containing basil plants and other leafy ferns. (TOS novel: The Rise and Fall of Khan Noonien Singh, Volume 1)
While exploring a lost Human colony in 2267, Lieutenant Kevin Riley discovered a farm growing basil and tomatoes. (TOS novel: The Galactic Whirlpool)
Basil was added to sour cream for asparagus dishes prepared in the food processor units aboard the USS Enterprise (NCC-1701). (TOS reference: Mr. Scott's Guide to the Enterprise)
The mess hall chef aboard the USS Enterprise-C, while on an "Old Earth kick", would serve meatloaf with a tomato-basil glaze. (TLE novel: Well of Souls)