By Luke Sumpter

It may come as a surprise to many, but every time you empty your coffee grounds into the bin, you are effectively throwing away a very cheap, effective, and natural fertiliser that could be used to nourish your cannabis garden or indoor growing operation. Not only that, but coffee grounds can also help to cover up obvious smells and defend your crop against parasites and several other pests.

Coffee grounds[1] are easily accessible and may appeal to a wide variety of growers, especially those who are environmentally minded. Coffee grounds are entirely vegan, and using your own grounds or those sourced from the local economy means minimising the transportation involved. Organic coffee grounds can also be used for those who are especially concerned about pesticide use and aim to keep their garden completely organic.

Here are some of the main reasons why using coffee grounds in your cannabis grow is a fantastic idea.


Adding coffee grounds to your soil and compost mixes will add to the acidity of the soil. Cannabis plants thrive in an environment that is slightly towards the acidic side of the pH scale, preferring levels of around 6.0–6.5. Soil pH that is either too high or too low will impede the growth of your plants, so it is important to monitor these levels closely. Coffee grounds can be used as a “pH down” product, acting to reduce the pH of your soil if it is too alkaline. Additionally, it’s entirely natural and won’t harm the environment when disposed of later down the line.


Every time you remove the grounds from your coffee machine, they can be added directly to your compost bin. This waste material contains nutrients that will keep your cannabis plants healthy and vibrant. When added to a compost bin, as opposed to being dropped directly into the soil, coffee grounds serve as a green waste, which can then be mixed with carbon-rich brown waste such as straw and wood ashes. Such a mix is excellent to generate the heat needed to break down the materials into a good-quality compost.

Coffee grounds provide noticeable levels of nitrogen into the compost mix. This key mineral is vital to plants as it is a major component of chlorophyll, the green pigment that plants utilise in order to conduct photosynthesis. Using coffee grounds will offer your plants a good supply of this mineral and will help to avoid any potentially damaging deficiencies during the grow cycle.

Coffee Grounds In Compost For Cannabis Cultivation


As well as offering defence against parasites, coffee grounds are also said to assist against fungal invaders too, such as Fusarium, Pythium, and Sclerotinia. Perhaps one of the most challenging elements of growing cannabis is pest control and management. Many small creatures have an appetite for the nutrients within the cannabis plant and can do a great deal of damage to a crop when attacking in numbers. If spotted early, many invasions can be dealt with, although preventative measures are much more effective than curative ones. Coffee grounds offer multiple benefits when it comes to preventing pests from obtaining a foothold.

Firstly, the acidity of the material is reported to help stave off parasite infestations. Secondly, the small and sharp grounds have a micro-abrasive property. This means that insects making their way towards your plants via the soil may be put off due to the sharp minefield of coffee grounds that obstruct their path.

As well has offering defence against critters, coffee grounds are also said to assist against fungal invaders too, such as Fusarium, Pythium, and Sclerotinia.


Earthworm excrements provide beneficial organic materials for the soil. Worms are an important asset in many cannabis gardens, and act as little compost producing machines. Keeping worms for this reason is known as vermiculture. The worms add the organic materials they are given and their poop, or castings, are used as compost within the garden. Coffee grounds can be fed to worms, as long as they are given other organic materials to form a balanced food intake that isn’t too acidic.

External Resources:
This content is for educational purposes only. The information provided is derived from research gathered from external sources.

Are you aged 18 or over?

The content on is only suitable for adults and is reserved for those of legal age.

Ensure you are aware of the laws of your country.

By clicking ENTER, you confirm
you are
18 years or older