Roots Organics Big Worm pure and premium worm castings is a distinctive natural potting soil amendment. Our worms are carefully tended and fed an unparalleled blend of organic compost rock dust and kelp for exceptional quality castings. No fillers no chemicals and no tricks. Just pure worm castings. Add Roots Organics Big Worm pure and premium worm castings to any potting soil as an amendment and conditioner.