From Discworld MUD Wiki
Radish is a vegetable of the (surprise!) Brassica family. While most radish varieties are grown for the edible root, some have been bred for their seeds. Radishes are also sometimes grown among other plants as a "trap crop".
This is a small, red radish, with thin white roots extending from the base. A small eye-shaped mark on the top of the radish squints at you evilly.
Radish can be found in the following locations: