Red Cabbage Seeds

Plant these in the summer. Takes 9 days to mature.
Overview
Red Cabbage Seeds are a type of seed that can be obtained from a variety of late-game and random sources, and they grow into 
They can be purchased at 

Combat and exploration can also yield Red Cabbage Seeds. In the Skull Cavern, they may drop from slain Mummies, Serpents, or Purple Slimes, though the chances are very low. Treasure rooms can also contain them, with a small chance of awarding between 5 and 20 seeds at once. Because of these multiple acquisition methods, players can obtain the seeds either through buying, crafting, or dungeon farming depending on their stage of play and available resources.
- Stone's General Store sells them starting in Year 2.
- The Magic Shop Boat at the Night Market sells them on Winter 16 starting in Year 2.
- The Traveling Cart may stock them randomly.
- A Seed Maker can create them from a processed Red Cabbage.
- Skull Cavern enemies and treasure rooms can drop them.
- Mature plants produce Red Cabbage, which can then be replanted or processed for more seeds.
Official description
Plant these in the summer. Takes 9 days to mature.