Can you reuse potting soil from containers?
Written by
Julia Anderson
Reviewed by
Prof. Charles Hartman, Ph.D.When properly done, potting soil can be reused from containers to help save resources. Over time, the structure and nutrients in old soil degrade. Pathogens can build up in soil that has not been treated. You can safely refresh the soil and restore its vitality with proper techniques. As a standard process, you should discard potting soil if it comes from a diseased plant to prevent contamination safely.
Sterilization Phase
- Remove debris: Shake out old roots and stems
- Spread thin: Layer soil 2 inches deep on tarp
- Solarize: Turn daily under full sun for 7 days
- Test moisture: Ensure complete drying before storage
Rejuvenation Phase
- Amendments: Blend 30% compost + 15% perlite
- pH adjustment: Add lime if below 6.0
- Nutrient boost: Mix 1 cup worm castings per gallon
- Moisten: Dampen mix before replanting
Solarization successfully utilizes ultraviolet (UV) light. Move soil onto a tarp in shallow layers for best results. Turn the soil on the tarp daily to ensure the soil gets even sun. Sunlight alone can kill pathogens in soil without the use of any chemicals. Solarization also preserves beneficial microbes from the soil. Ultimately, solarization of the soil should occur during a week of sunny days.
Reinstate structure through perlite amendments. Used soil compacts over time, filling in the air pockets that once existed. To improve porosity, add 15 - 20% fresh perlite. You can also mix the perlite with coarse sand to help improve drainage. Before replanting, it is recommended that you check drainage. To check drainage, squeeze a handful of soil and look for clumping tendencies.
Correctly identify unrecoverable soil. Discard at once if the plant exhibits signs of disease. Do not use soil that has sustained mold or insect infestation. There should never be the reuse of hydrophobic soil that repels water. Replace soil in containers that develop odors, particularly a dead or sour smell. It can be a health and safety consideration that limits disease outbreaks in the garden.
Soil that has been adequately refreshed operates almost like new soil. Nutrient levels are comparable to those of commercial potting mixes. Soil structure supports and encourages the development of robust root systems. Disease risk is dramatically reduced. Utilize and implement these techniques to support a sustainable container gardening practice, season after season.
Read the full article: Choosing the Best Container Gardening Soil
