Plant food and fertilizer
May 1, 2021

By Kate and Len Lucas

This subject has more folklore, myths and legend than King Arthur. If you look on the shelves in a garden centre you will find no end of boxes and bags of plant food. There’s one for Clematis, another for roses, one for Azaleas etc. Do we have to have one of each in the shed to make our garden grow? You can if you wish. Our approach to this subject is based on the whole concept of making life easier rather than studying for a degree in chemistry.

 A little background. Of all the things that could be in a feed, three things must be in it. These are Nitrogen (N), Phosphorous (P) and Potassium (K). The bold letter in brackets is the chemical symbol and the reason why Potassium is K is because the Latin for potassium is Kalium.

These three ingredients are fundamental to healthy plant growth and each does a different job. Nitrogen keeps things green, which is why they use lots of it on a golf course, phosphorous is important for flowers and roots and potassium helps fruit and seed to set.

So if you want a green lawn, you need more nitrogen than the other two and if you want more flowers and seed pods on the border you need much less nitrogen but more of the other two. So how do you choose what you need?

On the back of these containers of plant food, it will state the percentage of each of these three ingredients and they will be referred to by their chemical symbol – N, P and K. They are always referred to in this order and is called the NPK analysis. 

For example, the old-established fertilizer Growmore has an analysis of 7-7-7. That means it contains 7% of each of these ingredients and is referred to as a balanced all-round fertilizer. You can use it almost anywhere you want.

So after years of experience what do we do? Our regime for feeding the garden involves only three products:

 Fish, blood and bone (3-9-3) sounds spooky and as far as we know it’s the only place on the planet where these three things are meant to be together. We buy it in a large bucket-like container. It is a dry powder which we use by hand, as it is, directly onto the soil. We use it once in the spring around as many plants as we can treat, including the compost for the pots. It gets the garden going and keeps working away in the background. Although not strictly a slow-release fertilizer we treat it like one. 

Miracle-Gro Lawn food (36-6-6). That’s a whopping 36% nitrogen, exactly what you need for a green lawn. The phosphorous and potassium have been reduced to 6% each. It’s a soluble powder which we use in a spray attachment on the end of a long hose pipe. First applied in spring and possibly twice more if we think the grass needs it but before the hot weather arrives.

Miracle-Gro All Purpose Plant Food(24-8-16) also a soluble powder. Using a watering can it goes on the borders or pots where we want active green growth, but not like a lawn. With 8% phosphorous and 16% potassium it promotes flowering and all-around healthy growth. 

And our final thoughts are on the magical subject of making your own compost. You will hear many famous gardeners going on about how to do it and how great it is. All of which is good sound advice and very worthwhile.

However, to make a decent amount of compost you need a garden that produces a load of plant debris, two acres should do it. And if your garden is that big then our advice is to get somebody in to remove it. What they decide to do with it is their affair. We gave up making compost years ago because it is just too much of a faff. While we are at it when it comes to making leaf mould, apart from needing a load of leaves, the United Kingdom is likely to change government before any of it is ready to use.

We buy our compost in bags ready-made for use – simples.