NPK (nitrogen, phosphorus, and potassium) are the main nutrients necessary for plant growth. Early on during the Great White Shark grow (day 9) I used 5-15-5 nutrients, the numbers 5-15-5 are percentages of each nutrient in the mix, 5%-15%-5% with the remainder of the mix being filler material. 

  • Nitrogen plays a role in leaf development, it helps your pot plants get taller
  • Phosphorus helps in root and bud development
  • Potassium usefulness overlaps Phosphorus, but also helps plants in disease resistance

When a plant is young a high phosphorus amount (5-15-5) is useful for root development. Later on during vegetative growth I use a 20-20-20 formula (day 25 GWS grow), some growers will also use a higher nitrogen formula (ex. 12-4-8) to get their plants to grow taller. About 2 to 3 weeks into flowering I once again use a formula with a higher phosphorus amount; 10-15-10 (day 69 GWS grow), at this point the higher phosphorus will help induce bud development.

Late into flowering I use a budding formula; 1-5(day 101 GWS grow), the budding formula is high in Phosphorus and Potassium, but very low in Nitrogen, during the late stages of flowering a plant requires less nitrogen and more phosphorus and potassium, the late stages of flowering are mostly about growing bigger buds instead of wasting energy on growing leafs. 

If the various nutrient amounts are too complicated or not available, it’s perfectly fine to use something like a 20-20-20 or at 10-10-10 formula from start to finish of the grow, your plants will grow just fine. Using the specialized formulas will only get you that extra little bit, but it is more complicated, if you like to keep things simple go with a 20-20-20 from start to finish.

Be precise about nutrient amounts, I use measuring spoons. Nutrient brands will have different recommendation amounts for perennial, potted indoor, and outdoor plants. I use recommendations for perennial or potted indoor plants. Another thing I like to do is use half of the recommendation, but feed more often. For example if on the label it says to use 2.5 ml every 2 weeks, I will use 1.25 ml each week, this way there is a steady amount of nutrients in the soil all the time, as opposed to having a lot at the beginning of the 2 week schedule and very little if any at the end.

  • Throughout the GWS grow I used store bought nutrients
  • I didn’t bother with overpriced labels unless nothing else was available
  • the 1-5-4 I used on day 101 was overpriced, but I couldn’t find anything cheaper 
  • I will try looking for something more reasonably priced and put it in the store

Micro-nutrients/Secondary Nutrients

In the past, I used to always neglect micro-nutrients. Then I ran into a micro-nutrient deficiency during the GWS grow (Day 16). Now I pay attention to micro-nutrients. Only small amounts are required, but they are an absolute necessity, marijuana plants will run into a lot of problems if there is a micro-nutrient deficiency.

Micro-nutrients;   boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), 
molybdenum (Mo), zinc (Zn)

Secondary Nutrients;   calcium (Ca)magnesium (Mg), sulfur (S)

Primary Nutrients; Nitrogen (N), Phosphorus (P), Potassium (K)