Whether you are growing plants in a container outside by the patio, houseplants in pots inside the house, or are starting seeds, you never want to use a material that contains any soil or dirt from outside. You always want to use what is called a “soilless” potting mixture. The best soilless mixes are made of a combination of Canadian sphagnum peat moss, perlite, and vermiculite. Some products will have added some slow release fertilizer, water saving polymer gels, or some special root microbes called mycorrhizae.
Years ago the folks at Cornell University Ag School came up with what is considered the best recipe for a soilless mix for commercial growers. It is
Cornell Soilless Mix (adapted for organic growers*):
• 1/2 cubic yard peat moss
• 1/2 cubic yard perlite
• 10 lbs. bone meal
• 5 lbs. ground limestone
• 5 lbs. blood meal
We would not use the blood meal which is a fertilizer; it is a source of nitrogen.
THERE ARE OTHER PRODUCTS THAT CAN BE ADDED TO A SOILLESS MIX BUT ALL OF THEM ARE DEFINITELY OPTIONAL.
SEAWEED OR KELP
Seaweed powder or liquid added to the mix can protect the young plants from stresses
Comost has minerals and enzymes that will be beneficial to seedlings as they start to grow
Using Polymer Gels
Mixed with potting soil that is used for starting seeds, Polymer Gels foster improved rates of seed germination. The Polymer Gels hold water in the soil, insuring the consistent moisture that is so important for good seed germination.
Its presence also dramatically reduces shock from lost moisture when seedlings are transplanted.
Later when seedlings are set out in an established bed that does not have Polymer Gels in the soil, add little pockets of the gel and soil mixture in the area around each transplant.
For a detailed explanation of how water absorbing polymers work and why they are helpful, go to Using Water Absorbing Polymers.
For information about buying Water Absorbing Polymers click here to go to the Yardener’s Tool Shed.
We offer several soilless mixes for outdoor containers in Yardener's Tool Shed; click here