Supersoil Potting Soil A premium all-purpose potting mix for both indoor and outdoor containers. Top quality ingredients combine to keep soil aerated and to ensure proper drainage - Canadian sphagnum peat moss, ground fir bark, high-quality compost, and clean sand. Supersoil does not compact and holds just the right amount of water. Guaranteed fertilizer levels help plants grow and stay green. Nitrogen both fast-acting and slow-release to keep feeding for up to 90 days. Plus, phosphorus, potash, and iron.