NPK Ratios Explained

Why NPK ratios are so important when growing cannabis.

NPK is an acronym for Nitrogen (N), Phosphorus (P), Potassium (K) – Three nutrients cannabis plants must have in order to grow properly – into big healthy bushes, producing the biggest, sweetest, most aromatic buds possible. These are referred to as N-P-K Fertilizer Ratio when looking at a bottle of cannabis growing nutrients. The numbers on the ratio chart will be seen as something like this: 15-20-10 – which means there is 15% Nitrogen, 20% Phosphorus, and 10% Potassium… which would account for a total of 45% (15+20+10), which leaves 55% for inert ingredients. When growing marijuana, something very important to remember is that NPK ratios vary between the vegetative and flowering stages. Marijuana plants in the vegetative & early bloom stages require a higher nitrogen ratio, often labeled as PART A or PART 1, as it is the most important component for optimal growth. Once the cannabis plant begins flowering, you’ll want to lower the nitrogen and raise the phosphorus NPK ratios. These are known as PART B or PART 2. Something to keep in mind is that NPK fertilizer ratios do NOT include micro-nutrients, the trace elements found in most soils – which means you’ll need to add these if you’re growing hydroponically as there won’t be any soil used. If your waters calcium is above 200 PPM, adding more calcium may be counterproductive. The best thing to do is find a high-quality micro-nutrient made specifically for hard water. Fox Farm is one of the most commonly used for growing marijuana. Because there are legal issues with large-scale formulation testing, it’s been impossible to get a general consensus on what the perfect NPK ratios is for cannabis plants. Many companies are basically making low-quality products and trying to market them as “THE BEST.” Always stick with the brands that have a proven track record – my favorite cannabis growing nutrients have always been General Hydroponics as they have ALWAYS performed as advertised. Fox Farm is another I frequently use.

General Hydroponics Nutrients NPK ratios for growing cannabis plants

Vegetative Stage = FLORA GROW: 2-1-6

Flowering/Bloom Stage = FLORA BLOOM: 0-5-4

Advanced Nutrients NPK ratios for growing cannabis plants

Vegetative Stage = CONNOISSEUR PART A: 4-0-4

Flowering/Bloom Stage = CONNOISSEUR PART B: 1-5-6

If any of this seems like it’s too much to learn, my best advice would be to watch my videos and see how well the nutrients I used work, and then just copy what I do with you cannabis grow. It’s proven effective. Using a basic NPK ratio is the easiest way to learn, as it keeps everything cut and dry, making cannabis growing as easy as possible. Overthinking often leads to failure, keep it short and simple.