To provide a plant processing method which enables further improvement on the prevention of deterioration and the long-term storability of a plant.

The plant processing method comprises forming a film of a liquid polysilazane-containing coating material on the surface of a plant base material and converting the polysilazane to silica, to form a coating layer. The plant processing method further comprises forming a film of a liquid polysilazane-containing coating material on the surface of a plant base material, converting the polysilazane to silica, to form a primary coating layer, and forming a secondary coating layer of an organic material on the primary coating layer.