Vermiculite is a common component of soil-less growing mediums for vegetable seedlings. It is used for its ability to hold moisture, provide aeration, and regulate soil temperature. Vermiculite helps to keep the growing medium from compacting, which can suffocate the roots of the seedlings. Additionally, it helps to prevent soil-borne diseases and provides essential minerals that seedlings need to grow and develop. Vermiculite is often mixed with peat moss or coconut coir to create a well-draining, nutrient-rich growing medium for vegetable seedlings.