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Why Fertilizer Isn’t Plant Food – Mind. Blown

Why Fertilizer Isn’t Plant Food – Mind. Blown

Plants don’t need much, just a few basic things to live. These basics are air, water, light and minerals.

No mention of food or fertilizer !

That’s because plants are autotrophs. Crazy name I know but it means they have the ability to create their own food. All they need is the following ingredients:

  • Air which supplies carbon dioxide to the leaves, stems, flowers & roots.
  • Sunshine produces the light energy needed.
  • Water moves all the goodies around.
  • Minerals that are drawn up from the soil or potting mix.

Not Paying Attention At The Back?

Plants have their own solar-powered food factory using light energy from the sun. The green part in plants, chlorophyll, reacts with the carbon dioxide and produces glucose – dinner time.

This process is called photosynthesis and thank goodness for it because the by-product is oxygen.

Without plants making their own food, we wouldn’t have oxygen to breathe.

So Fertilizer Isn’t Plant Food Then?


The fertilizer you can put on your plants to boost growth doesn’t actually feed them.

Fertilizer contains minerals that help in the photosynthesis process. Some of our soils are not so rich in these minerals today so it is a bit like taking a supplement to help with some of those shortages. This is especially important when growing in pots. Your plant is reliant on what you provide so be kind to her and she will flourish.
What Exactly Is Fertilizer If Not Plant Food?

So when I go looking for fertilizer what do I need to look out for. Look carefully and each bag will generally have something like this written on it – N P K plus trace elements.

What does this all mean, let’s take it one at a time.

N stands for Nitrogen and is for leaf growth and greening up your plant

P is for Phosphorus that helps with healthy roots and shoots

K is for potassium and it keeps those flowers and fruits coming

The different numbers next to NPK are shown as the ratio of Nitrogen to Phosphorus and Potassium. Too much Nitrogen and the plant will put it into leaf growth, not enough and they will look pale in colour. Higher Potassium and flowering is better. You know how it is – it’s all about the balance.

One more thing, when you see 8-9 months or 3-4 months on those fertilizer bags, it simply means that the fertilizer slowly releases over that period of time. Sometimes a little faster if the temperatures are hotter. 

But hold on cause that’s not all.

There are secondary minerals that plants need too. Calcium to grow strong cell walls, magnesium to harness photosynthesis, and sulphur to help the nitrogen work.

There are also trace minerals such as chlorine, iron, manganese, and zinc plus others which are needed in the smallest amounts but are still very important.

Without these minerals (plus water, air, and light) plants develop deficiencies, they discolour, wilt, can’t grow and flower or the shoots become stunted. When plants are unhealthy, it also makes them prone to disease just like humans really.

Deficiencies mean there’s something missing that can’t allow the plant to perform its normal processes to promote healthy growth.

But Wait….

Don’t assume because the plant looks unwell you need to give it a big dose of fertilizer. In fact, you can do more harm than good. Too much fertilizer is just as bad as too little and if your soil is the wrong Ph levels then you could be only wasting time.

Let’s problem solve

  • Are you watering correctly? Not enough water means the plants can’t transport it’s food where it needs it and too much water will rot its roots and prevent mineral take up. Make sure your soil drains freely and doesn’t become waterlogged.
  • If you’re watering the right way and your indoor plants still look sick how about the light level? Try putting it in a brighter spot (but not direct sunlight that will burn the leaves). 
  • Still not working? Then a solution of fertilizer may help, especially if your plant has been in the same container for years or your outdoor garden needs a bit of a spruce up. Always follow the dosage instructions because too much fertilizer is poison and you’ll witness a gradual wilting death over the course of a few weeks. 

This Way For Healthy, Happy Plants

Looking after your plants isn’t hard work because they don’t need much to make their food.

Just make sure they have enough light, just moist is just right, use a free-draining soil and use a good quality liquid feed every once in a while and our tip for getting the moisture levels right is our new best friend, ‘Sustee’.

Having the right combination of The Big Four means you’ll have a room or garden full of lush green foliage, large scented flowers, and happy oxygenating autotroughs.

What could be better?

Oh, and in case you were wondering about the word autotrough - ‘auto’ comes from the Greek for ‘self’ and ‘troph’ which is the Greek for ‘feeding’.

Plant nerds – we love a bit of Ancient Greek.

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