The primary nutrients in plant foods are Nitrogen (N), Phosphorus (P), and Potassium also called Potash (K).
In addition to nitrogen-phosphorus-potassium, plants require a lesser amount of secondary nutrients and trace quantities of other elements.
Secondary nutrients are calcium, sulphur, and magnesium. Trace elements are small quantities of boron, chlorine, cobalt, copper, iron, manganese, molybdenum, and zinc.
Plant foods are measured in an N-P-K format
N is Nitrogen
P is Phosphorus
K is Potassium (Potash)
A 7-4-3 plant food contains:
A 30-15-15 plant food contains:
The percentage of the solution not used by nitrogen-phosphorus-potassium is secondary nutrients, trace elements, and/or inert material.
An all purpose nutrient with secondary nutrients and trace elements will get you through all stages of growth. But during different stages of life, you can adjust the nutrient levels to optimal quantities.
Regardless of the nutrient you choose, during the first 1-2 weeks of life and the first 1-2 weeks of flowering, use half the amount (or less) of nutrient solution the manufacturer recommends.
That is, if the nutrient package says to mix one tablespoon of nutrient to every gallon of water, you should add less than half a tablespoon of nutrient to every gallon of water for the first 1-2 weeks after germinating or cloning, and when flowering is initiated.
This is not essential when flowering, unless the plants have just been transplanted, but it is for seeds and clones. Some growers don’t add any nutrients to the water for the first 1-2 weeks.
They then use a 50% solution for 1-2 weeks, then go to a 100% solution.
During seedling/vegetative growth the plants need lots of N (nitrogen).
They also need a fair amount of P (phosphorus) and K (potassium), 7-4-3, or 30-15-15, or something with a similar ratio of N-P-K, and secondary nutrients, and trace elements will work.
During flowering the plants need more P (phosphorus) and more K (potassium) than they did during vegetative growth.
They need some N (nitrogen) but not as much as they did during seedling/vegetative growth. They also need secondary nutrients and trace elements.
If you used:
— Something like 7-4-3 for seedling/vegetative growth, then try using 4-8-7 (or similar ratios of N-P-K) for flowering.
— Something like 30-15-15 for seedling/vegetative growth, then try using 15-30-30 (or similar ratios of N-P-K) for flowering.
Two and three part nutrient solutions, that allow you to custom blend the amount of the different components, are recommended.
Organic nutrients are available but they can be harder to find.
Do not give your plants extra nutrients thinking it will make them grow faster. Too much will kill your plants. If you under fertilize, plant growth will be slowed but they will stay alive much longer than if they got too much. Follow the mixing instructions on your soil nutrient package, if you aren’t sure, use less rather than more.
Stop all plant food at least 14 days before harvesting when growing in soil. The last few times you water the plants, don’t add any nutrients.
You can repeat this water only ‘feeding’ several times in the 2 weeks prior to harvest. When growing in a hydroponic garden, stop all plant food at least 7 days before harvest.
This is so N-P-K and other elements can be removed from the plants before harvesting. This will ensure that your plant doesn’t taste like plant food, and you are ingesting a minimal amount of N-P-K, secondary nutrients, or trace elements. See when to harvest your crop for more info.