Using worm castings in soil with growing cannabis

Using worm castings in soil with growing cannabis
Luke Sumpter

Take a look at why worm castings are a popular and natural method of providing great soil health, and how to optimise their use for your green-fingered grow.

Worms are a crucial part of providing life and health to the soil we rely on to survive. They have lived on planet Earth for millions of years and are a natural fertiliser, generating a growing environment for plants, that is rich in nutrients and minerals, so that plants can survive and thrive.

This is achieved as the worms break down the organic matter in the soil by passing it through their digestive system. Worm casting literally means the material, that has been passed through the worm back into the soil.

Castings are packed with bacteria, fungi, protozoa and nematodes, which revitalise the food web of the soil, aiding in its beneficial functions. They appear as tiny oblong particles of worm manure.


Bacteria and protozoa help to nourish the soil, while protecting against and repressing disease. The bacteria produces a nitrogen-fixing process, which means, that it converts the nitrogen into a form, which plants can harness during photosynthesis. The protozoa releases nitrogen, that aids the plants as they take in the bacteria, fungi and other protozoa, that exist in the soil.

Some of the fungi in worm castings will decompose the dead organic matter, such as manure or leaves. Mycorrhizal fungi is a symbiotic component, which will colonise plant roots and make phosphorous soluble. This helps to stimulate the growth of roots and increase the plant's resistance to disease.

Nematodes also play an important role in soil health. They are multicellular animals, which feed on the unwanted bacteria and fungi, as well as other nematodes, releasing beneficial bacteria and fungus back into the soil.


Worms move around in the soil, allowing for circulation of water and air, which helps to keep the soil healthy by preventing compaction while retaining water. This provides resistance to drought.

Worm casting aids in the breakdown of organic matter, such as decomposing food waste or vegetables and other organic materials. This is known to enrich the nutritional and mineral content of soil tenfold and helps to keep pH levels consistent.


The humus created by worms is rich in organic matter and is an ideal fertiliser for healthy roots and lush plants. What's more, the soil produced by worms does not create a bad smell - a key indicator of healthy worm castings.

It is important however, to bear in mind, that plants cannot live on worm castings alone. Using too much can prevent or stagnate the plant's growth. The best mix for plants is around 1 part castings to 3 parts soil. Sometimes even a 4:1 ratio is recommended. Established plants only require around 6mm of worm castings.

The efficiency of the casting is dependent on the nutrients and minerals the worms consume. They require the correct variety in order to have a well-balanced nutritional content.

Ultimately, efficient use of worm castings provides a more rapid seed germination and plant materialisation in the early stages of growth. As the plant grows, castings aid in balanced root development and plant vigour, boosting the growth rate.


For most growers it's more reliable and easy to have the worms shipped in "worm cans". This means, that the worms are more likely to be of high quality so as to produce the optimal content of the correct nutrients you need. Worm castings are also safe to use around children and pets.

Today, worm castings are made with strict regulations and quality control in order to achieve the perfect biological consistency. They are usually produced in high volumes using dairy or horse manure. The worms are specifically chosen to withstand a range of environmental conditions in the soil, such as water and food levels, temperature and pH.

This allows cannabis growers to maintain a cost-efficient, sustainable support in their operation - from germination to harvest.


Worm castings promote soil health without the use of chemicals, generating less entropy and maintaining a rich natural taste in the finished product. Farmers have used this method for thousands of years and still practice it because it's simple and they can raise worms on their own if they wish.

Natural soil means an all-natural and organic plant. Using chemicals can alter the taste of the product you are growing. A healthy worm casting is essential for farmers to get the most out of their soil, while enjoying a green-fingered approach to growing.

Luke Sumpter
Luke Sumpter

Luke has worked as a cannabis journalist and health science researcher for the past seven years. Over this time, he’s developed an advanced understanding of endocannabinoid system science, cannabis phytochemistry, and cultivation techniques.