Which of the following media types is not mineral-based?

Pine bark is the correct answer as it is an organic material derived from the outer covering of pine trees, rather than a mineral-based medium. Organic media play a crucial role in greenhouse management as they contribute to soil structure, enhance moisture retention, and provide nutrients as they decompose. In contrast, the other options—perlite, vermiculite, and sand—are all mineral-based. Perlite is a lightweight volcanic glass that is expanded by heat, providing aeration and drainage. Vermiculite is a hydrous phyllosilicate mineral that expands when heated, contributing to moisture retention and aeration. Sand, while naturally occurring and mineral in origin, primarily acts as a drainage amendment. Recognizing the differences between organic and mineral media types is essential for effective greenhouse management and for creating optimal growing environments for various plants.