Unless there has been a disease or invasion of some kind, there is no need to buy new soil every time you want to pot a cannabis plant or repot existing plants. Simply reuse the old stuff. Revitalising and reusing old soil is easy and a great money saver.

Marijuana is a notorious glutton for nutrients of all kinds; nitrogen-hungry during vegetation and calcium and magnesium-demanding during flowering, cannabis will always leave soil depleted. With that said, there are numerous benefits cannabis provides as well; the roots fluff out and the overall soil structure is improved upon. Such is one of the many upsides to growing cannabis.


By keeping soil healthy to begin with, you can prevent the need for its radical rehabilitation prior to reusing. Regular fertilising, composting, and mulching of potted plants with ensure healthy soil at every stage of its life. When well-cared-for soil maintains its health, friability, water penetration and retention, it needs little modification when reused.

Companion planting also helps keep soil healthy, vital, and disease-free. When doing this, however, it’s advisable to plant in a bigger pot than necessary to allow room for companion plants to grow. A simple alfalfa, clover, and marigold mix will provide manifold benefits to plant and soil health.

Organic Soil Cannabis Association Crops


Uncared for and stressed soils will require amending prior to reuse. The soil may become hydrophobic, completely exhausted of nutrients and minerals, or with a collapsed structure. Soil that has been left to bake in the sun will certainly be leached of nutrients and will need to be modified.


If your soil was invaded by a pathogen or is quite unhealthy for whatever reason, the best thing to do is simply put the soil in a bag and discard. Mixing it into garden beds or working it into compost could spread the pathogen to your whole garden. Sometimes, diseases can linger in soil even after you think they’ve left. This is true for several species of mite, fungus, gnat, and rot. Reusing the soil will certainly infect the new occupant. Be sure to wash your hands before touching healthy soil and plants. Wash the pots as well in warm, soapy water to ensure the vector has been scrubbed away.


Pasteurising old soil is a way to get rid of a number of unfriendlies. Grass and weed seeds, insect eggs, and fungal spores can all be killed by putting the old soil in a black garbage bag, then leaving it to bake in the sun for an afternoon. The heat will pasteurise the soil to be ready for use. It will also kill most of the friendly biota, so you are committed to soil-amending once you decide to pasteurise. Bake in the sun before amending so you don’t kill all the friendlies you add.


Before reusing soil, it must have its texture and fertility improved.

The quickest route to healthier soil is to add 50:50 new potting mix to the old soil. Commercial potting mixes have the disadvantage of drying out quickly and they tend to be compact and have poor structure. They can be expensive, especially if you have a few pots to fill. They do, however, have the advantage of being an instantaneous solve to poor-quality soil and take little effort.

Depending on your outlook towards organic soil structure, you might not like the idea of wetting agents and crystals, slow-release industrially-sourced fertilisers, or hormone enhancements. Perhaps a more hands-on approach to the mystic potion for bigger buds is what you prefer. These ingredient guidelines will ensure you make a rich and well-draining, life-enhancing soil.

Fresh Cannabis Substrate

Adding compost is the most natural solution to improving soil. A 30:70 mix of compost will provide much needed nutrients and structure to depleted soil. If you are not a composter, there are commercial composts available.

  1. If you would rather make your own organic soil, try this recipe: Volume for volume, add presoaked coco coir, coarse sphagnum moss, or peat moss to the depleted soil.
  2. Add vermiculite, perlite, or course sand until friable. Perlite increases the surface area for friendly bacteria particularly well.
  3. Add compost, bat guano, worm castings, blood and bone, or old mushroom compost to provide essential nutrients.
  4. Add crushed rock dust, dolomite, epsom salts, and molasses to provide a range of vitamins and minerals.
  5. Adding a splash of microorganisms to any soil mix is beneficial. Burgeoning colonies of beneficial root bacteria make plants hardy in the face of weather and disease, pests, and poor pH. They also help decompose old roots into beneficial compounds for new plant growth.
  6. Alternatively, old soil can be reused in other ways:
  • Add it to compost 
  • Dig it into garden beds
  • Fill holes and divots in your yard
  • Add to the bottom of planting holes

Building higher-quality soil with organic matter reduces plant stress, improves disease resistance, and saves you money. Well-structured soil retains water, yet drains well and promotes a healthy root zone. This optimises healthy growth for the life of the plant. Add slow-release fertiliser pellets or water monthly with a liquid fertiliser like fish or seaweed emulsion. Regular maintenance means the soil will need less attention next time it is reused.

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