Mississippi State Trial Garden Potting Soil Recipe
Basic Large Container Mix
15 gallons composted fine pine bark (soil conditioner)
5 gallons sphagnum peat or peat-based bagged potting soil
3 cups controlled-release fertilizer (e.g., Osmocote, Nutricote)
1½ cups dolomitic lime (garden lime)
½ cup micronutrient fertilizer (e.g., Micromax)
wetting agent (optional)
- Break up clumps of sphagnum peat if using compressed bales.
- Combine pine bark and sphagnum peat. If using a powdered wetting agent, add it now.
- Add a small amount of water—just enough to reduce dust during mixing. If using a liquid wetting agent, add it to this water.
- Blend the pine bark and sphagnum peat until the mix looks uniform.
- Add fertilizer, lime, and micronutrients and mix until well blended (no clumps).
- Add water slowly while mixing until the mix is moist but not wet.
- Transfer the mix to your container, and shake the pot to settle. Avoid packing or tamping the mix.
- Plant your selected plants into the container.
- Top-dress the pot with the appropriate amount of fertilizer for the plants.
- Water in your new transplants very well, but slowly. You want to water until water begins draining from the holes in the bottom of the pot.
- If saving leftover potting mix, read the comments to learn about the steps to use it later.
- This mix is intended for large containers. Pots larger than 6 inches are what we consider large.
- If the controlled-release fertilizer you select has micronutrients included, you will not need the additional micronutrient fertilizer.
- Other fertilizers can be used, but the amounts will need to be adjusted to deliver an equivalent amount of nutrients. ONLY slow- or controlled-release fertilizer should be used.
- The fertilizer in this recipe is only a starting amount. You will need additional fertilizer to ensure optimal plant growth.
- If you are growing plants that are acid lovers, reduce the amount of lime by half (add only ¾ cup).
- If you save extra mix for later, keep it in a dry location. Make sure to water in very well immediately after planting. Water until the water runs clear from the holes in the bottom of the pot. This will prevent salt damage. Water as normal from then on.
The information given here is for educational purposes only. References to commercial products, trade names, or suppliers are made with the understanding that no endorsement is implied and that no discrimination against other products or suppliers is intended.
Publication 3409 (POD-01-20)
By Geoffrey Denny, PhD, Assistant Extension Professor, Plant and Soil Sciences.
Copyright 2020 by Mississippi State University. All rights reserved. This publication may be copied and distributed without alteration for nonprofit educational purposes provided that credit is given to the Mississippi State University Extension Service.
Produced by Agricultural Communications.
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