BLOCKS OR TRAYS! Whether you are starting your seeds in plastic trays or using a soil blocker, Seed Starter is the mix for you READY-TO-USE! Purple Cow Seed Starter Mix is a blend containing everything needed to start seeds including enough fertility for up to 45 days COMPOST BASED! This mix is created using our Activated Compost, a premium soil amendment with over 20 years of growing success STURDY SEEDINGS! Promotes rapid germination and vigorous seedlings with strong root systems able to withstand transplanting and thrive all season long