Spawns as part of a Leafy Garden (Frost Garden - As of version 1.8.9)
Spinach leaves can be crafted (shapeless) into seeds and planted in tilled dirt
Spinach plants can be right-clicked to harvest and it leaves the plant to grow again.
Recipes[]
Stock = Pot + Spinach
Steamed Spinach = Pot + Spinach + Water
Spinach Pie = Bakeware + Dough + Spinach + Cheese + Toast
Beef Wellington = Raw Beef or Firm Tofu + Dough + Any Mushroom + Spinach