How can I boost a basic potting mix?
Answer: Instead of creating a custom potting mix from scratch, you may choose to purchase a basic commercial mix and boost it with additional organic amendments. This allows you to save time mixing bulk ingredients, but still end up with a premium potting mix. A basic “peat-lite” mix, composed primarily of peat moss and perlite and/or vermiculite, makes a good foundation for a custom mix. These commercial mixes already have a balanced pH and contain an organic wetting agent to help the peat moss absorb water. A starter fertilizer is usually included in commercial peat-lite mixes, but you may choose to add additional organic fertilizers to reduce the amount of supplemental liquid fertilizer that needs to be applied. Also, high-quality compost and vermicompost can be added to a commercial mix to increase moisture retention, add nutrient value, and provide beneficial microbes to support plant health and speed the mineralization of organic fertilizers. Other biological amendments, such as mycorrhizal fungi and rhizobacteria, can also be added to improve the performance of a commercial blend. You will find a more detailed discussion of these amendments in the ATTRA publication Potting Mixes for Certified Organic Production. This publication covers considerations for an organic grower selecting a potting mix to use for transplant or containerized plant production or for someone wishing to blend organic media. It discusses individual components of potting media in addition to organic and biological amendments to improve plant performance. Several organic potting mix recipes are included in the appendix, in addition to suppliers of organic media and amendments.