Coffee As a Cannabis Fertiliser
Spent coffee grounds are a valuable and affordable organic fertiliser resource. The grounds and chaff from home-roasted coffee beans provide a rich source of nitrogen, one of the three essential macronutrients that cannabis plants need to thrive. Used coffee grounds can be applied directly to the soil, around the base of the plant, or mixed into the soil for gradual release of nutrients.
The pH of seed meals from spent coffee grounds ranges between 5.8 and 6.2, which is suitable for conditioning the soil. When coffee grounds are added to the soil, the pH levels may slightly increase. If non-bleached paper coffee filters were used during brewing, the entire coffee waste can be composted without causing additional environmental harm.
It's important to note that caffeinated content can be detrimental to the growing environment, so only spent grounds should be used—avoid using freshly-ground coffee. Fresh coffee grounds are generally more acidic than used ones, and fermented or rotting coffee grounds should not be used in gardening.
The nitrogen content in used coffee grounds takes some time to become available to plants because it must break down from its organic compounds. This means that adding spent coffee grounds to the soil provides a slow, gradual release of nitrogen, which benefits plants over the long term.
In addition to nitrogen, coffee contains trace amounts of other nutrients such as phosphorus, potassium, magnesium, copper, and calcium. These nutrients also require time to become accessible to plants.
Coffee grounds can benefit various other crops, including tomatoes, carrots, lettuce, blueberries, and radishes. Additionally, they can help deter garden pests such as snails and slugs. The smell of coffee grounds can even discourage cats from using your outdoor garden as a litter box.
How Do I Use Coffee Grounds in my Cannabis Grow?
You can fertilise your garden with spent coffee grounds in several ways. Here are a few ideas:
1. As a Soil Amendment: Mix the used coffee grounds six to eight inches into the soil. This will release macro and micronutrients to your plants while improving soil structure and aeration.
2. As a Side-Dressing Fertiliser: Feed the coffee grounds directly to the plants. Used grounds have a favourable carbon-to-nitrogen ratio, making them suitable for both plant and soil nutrition.
3. In Worm Castings: If you keep a worm bin, add coffee grounds weekly, mixing them with other kitchen waste. Your worms will appreciate the addition.
4. In Composting: Combine coffee grounds with other green materials. For example, layer one-third fresh grass clippings, one-third fresh leaves, and one-third coffee grounds in your compost pile. Be sure to turn the compost regularly.
5. As a Foliar Spray: Soak half a pound of used coffee grounds in five gallons of water. Use this solution to spray directly onto the plants, particularly on the undersides of the leaves.
Used coffee grounds are an excellent and inexpensive way to condition the soil. They enhance soil structure and fertility while providing essential nourishment for cannabis plants. Additionally, utilising coffee grounds is a fun way to manage kitchen waste!
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Liz Filmer
