Root
From Memory Alpha, the free Star Trek reference.
A root is an organ of a plant that obsorbs nutrients and typically lies below the surface of the soil. They often can be used as a food or as medical treatment.
During the disaster at Arvada III, Felisa Howard learned how to use roots to treat the sick at the colony, despite not being a physician. She would also teach her granddaughter, the future Beverly Crusher, this knowledge. The knowledge benefited Beverly when she became injured on the planet Minos, where she instructed Jean-Luc Picard on how to use roots to treat her injuries. (TNG: "The Arsenal of Freedom")
The Federation colonists that lived on a planet in the Orellius system attempted to use fungi and roots to cure the deadly infections caused by insect bites that were killing their people. (DS9: "Paradise")
Leola root was a well known food in the Delta Quadrant, renowned as a source of vitamins and minerals. It could be made into several types of food, such as a stew, soup, and a tart. (VOY: "State of Flux", "Parturition", "Riddles")
