Fertilizer can be confusing. The sheer quantity of brands and mathematical combinations can be dizzying. Let’s spend some time unwinding fertilizer and hopefully, the numbers will begin to make sense.
Nitrogen, Phosphorous, and K – Potassium (aka Potash) are the 3 major nutrients or macronutrients contained in fertilizer required for plant growth. They are the 3 numbers you see on fertilizer labels. These numbers represent the percentage of each macronutrient in the specific fertilizer. So if you see a label saying 20-20-20, it contains approximately 20% nitrogen, 20% phosphorus, and 20% potassium. The numbers aren’t adding up? The remaining percentage is made up of a smaller amount of nutrients known as micronutrients and fillers. The fillers help you the fertilizer spread evenly.
Joe Lamp’l of Growing a Greener World has come up with a great way to describe the functions of N, P, & K – just remember: Up, Down, & All Around.
N – nitrogen – UP – think ‘up’ or top growth
- nitrogen promotes green leafy growth
- healthy leaves mean a better-equipped system to provide food for the plant
- If you see a fertilizer with numbers like 30-0-3 – that would be great for a lawn because this fertilizer is all about green top growth.
P – phosphorus – DOWN – think ‘down’ or root development
- phosphorous promotes root development and flowering
- flowering means the amount of flowers and size of blossoms
- For ‘root boosting’ fertilizer, it is common to see combinations like these: 10-52-10 or 5-15-5
- A common ‘flowering’ fertilizer combination is 13-30-15
K – potassium – ALL AROUND – think good health in general
- potassium promotes overall health: guards against disease, aids in drought and cold tolerance, cell wall strength & maintenance
- Potassium also enhances fruit & vegetable flavor & development
- Vegetable fertilizers are rather conservative in and look like this: 7-4-5, 2-7-4
Our favorite fertilizer and the one that we use is called “Nature’s Best”. It’s a natural fertilizer and we find it easy to use, gentle on plants with no burning leaf tips, and we think it makes flowers brighter. ‘Miracle Grow’ is another good choice and other balanced fertilizers like 20-20-20 work well.
Hope that helps!