Humus

Worm humus - also called vermicompost or worm castings - provides cannabis plants with numerous nutrients and also improves soil texture. It provides humic and fulvic acids to the growing medium, as well as microbial life beneficial for the development of plants.

Even if used in excess (which we do not recommend), worm castings won't harm your plants.

Mix 10-30% of humus with the substrate.