288 Cell Seedling Trays for Plug Seed Nursery Trays the optimal air to water ratio within the plug matrix results in explosive early root growth,great for starting seeds when space is at a premium, the growing span of can be shorten by 10-20 days,is to support the requirement of the plant in the different plant stages, are also ideal for starting cuttings. ANTI-HIGH TEMPERATURE & DURABLE MATERIAL.