Quality - Soil Block Mix with Compost and Worm Castings - 12 Dry Quarts! All Natural Seed Germination Blend. The key to perfect soil blocks is the consistency of the mix. Developed and tested to promote excellent root and stem development for your new seedlings. Follow the manufacturers instructions for making the soil blocks using Green Planet Naturals Soil Block Mix. Plant and care for the seeds according to the instructions on your seed packet, being careful to cover the seeds at the depth specified on the seed packet. Made from Compost, Sphagnum Peat Moss, Coco Coir, Volcanic Pumice and Worm Castings.