What is NPK?

What is NPK?

Have you ever looked at the fertiliser section of your local nursery and wondered what the heck the three numbers are about? Or looked at the endless supply of 'growth' solutions feeling lost about which one you plant needs? Well, today we're going to break it all down for you and offer natural (and free) ways of adding vital nutrients to your potted plants. 

With fertiliser, there is an almost unlimited combination of ingredients, formulas and trade secrets - but you'll notice they all have one thing in common.

Whether it's from a small batch boutique company or a global supplier, there will always be a combination of three numbers on a fertiliser label, such as 5-5-5, 10-8-10 or even 0-0-0. You may ask yourself, "what do these numbers mean?" or "which ratio is best for my plants?".
Today, we're going to break it down.

What is NPK?

These numbers represent the values of the three major macro-nutrients used by plants. These are, nitrogen (N), phosphorus (P) and potassium (K), or NPK for short.
The higher these numbers, the higher the concentration of that given value. For example, an NPK of 10-5-5 has double the amount of nitrogen in it versus phosphorus and potassium. Whereas a 20-20-20 fertiliser is well balanced across the three macro-nutrients.

Why is it Important?

Nitrogen, phosphorus and potassium are the three major nutrients a plant needs to thrive and grow. Whilst organic matter, soil biology and natural minerals play a part in plant health, we will discuss them in future blogs. Well-fed plants are healthier and produce more growth, so it's important to remember that a plant will fail without any nutrients available.
Nitrogen (N) - Helps your plants develop lush green leaves. When plants don't receive enough nitrogen, leaves can turn yellow or pale green. Young plants that receive too much nitrogen may be stunted or "burned". z

You can find natural plant nitrogen in - Alfalfa meal, coffee grounds, clover crops, fish emulsion, grass clipping, human urine and so much more.
Phosphorus (P) - Improves the development of root growth and fruit and flower development. Phosphorus also helps plants use other available nutrients more effectively.
You can find natural plant phosphorus in - Rock phosphate, bone meal, vermicompost (earthworm organic waste), chicken manure, compost, dried lemon peel and so much more.
Potassium (K) - Potassium improves a plant's immune system, increasing its overall vigour and tolerance to external factors (pests, disease, drought). Not enough potassium can lead to stunted growth or scorched leaves.
You can find natural plant potassium in - banana peels, seaweed or kelp meal, cucumber skins, crab waste, granite dust, kaolinite (clay), wood ash, and so much more.
Adding fertilizer sticks to a green potted plant.

How Much Do My Plants Need?

As you can probably tell by now, there is no one clear answer when choosing a fertiliser that benefits all of your plants. Green houseplants that don't typically produce flowers should receive a fertiliser slightly higher in nitrogen. For example a 3-1-1 or even a balanced 5-5-5 fertiliser. If you grow flowering houseplants, such as a begonia, you would seek a fertiliser higher in Phosphorus (P). This could be a 1-3-1 fertiliser for example.

Whilst there is no clear-cut answer for a fertiliser that will benefit all of your plants, there are some easy solutions. With those of us who have a large range of houseplants, both green growers and flowering, we can get by with two fertilisers - one for plants that flower and one for those who don't.
A green watering can, watering a green plant in a green pot in the sunshine
There you have it; by now you have enough of an understanding of NPK and fertilisers to choose what's best for your plants. The most important thing is not to be turned away or get too caught up by all the numbers, scientific jargon and marketing tactics that fertiliser companies boast - remember that some fertiliser is better than none. At the very least, even a balanced fertiliser (such as 5-5-5) would benefit your plants more than not feeding them anything.
What changes you're going to make to your fertiliser selections? Or maybe you've already found the right one? Either way, let us know!