In his weekly Jamie’s Little Allotment column, gardener Jamie Marsh makes understanding fertilisers easy…
Tomatoes, cucumbers, aubergines and peppers are really doing well now in the greenhouse. Squash and pumpkins are making their way over the top of the arch, leaving behind lots of fruit and the runner beans have definitely started to run, right to the top of the wigwams, and are now covered in lovely red flowers and tiny beans.
When it gets to this point in the veggie growing season and the plants are doing what you hoped they would, it’s a good sign that all their needs are being met.
Aubergines are doing well this time of year down on Jamie’s allotment
Plenty of water, lots of lovely sunshine and an abundance of food in the soil are the three main things they need to grow into strong healthy plants and give us all that delicious produce.
But what some people forget is, when plants are growing at this fast rate, they’re using up huge amounts of nutrients from the soil. The last thing we want is for those nutrients to get depleted, slowing the plants down or setting them back.
So we might need to add some nutrients in the form of fertilisers. If you’ve read my column before, you’ve probably heard me mention that I don’t use chemicals on my veg plot, and I follow what’s called the ‘no dig way’ of growing, basically disturbing the soil as little as possible.
The way I get nutrients into my soil is by adding a layer of organic matter to the top in the spring, before the main growing season kicks off. The worms and insects drag this compost or manure down into the soil where the plant roots can access it. I always hope this will be enough to feed everything throughout the season, but sometimes it isn’t.
If I notice a particular part of the plot where plants look a bit stressed, I’ll mulch around that area with more compost and let the worms and rain top up those precious nutrients needed for great growth.
Another area that definitely needs lots of feeding at this time of year is the greenhouse. The plants in there are really hungry. Tomatoes, cucumbers and aubergines are pumping out fruit and need feeding far more often than those outside. I feed my greenhouse plants at least twice a week with an organic seaweed tomato food that’s high in potassium.
There are so many different fertilisers out there to choose from but which ones should you use? Liquids, powders, granules, pellets, foliar feeds, long lasting, quick acting, seaweed, nitrogen, phosphorus, potassium. What does it all mean?
I’ll try and break it down in layman’s terms. On most fertiliser bottles or bags you’ll see the letters: NPK. These stand for: Nitrogen (N) – Helps with leafy growth. So things like cabbage and kale love nitrogen. Phosphorus (P) – Promotes root growth. Essential for all plants, especially when they’re young. Potassium (K) – The big one for the veg plot at this time of year. It boosts flower and fruit growth.
Now that we know what NPK means, we can tailor fertiliser to suit the plants. In the greenhouse, we want potassium to help with fruiting. For leafy greens, nitrogen is key. All you need to do is read the back of the fertiliser bottle. It’ll have the N-P-K values listed. As a general rule, the higher the number, the higher the percentage of that particular nutrient. Most fertilisers will also give you a simple description of what they’re best for on the front of the packaging.
So which types should we use? Liquid feeds need to be diluted. The bottle will tell you how many millilitres per litre of water. Some granules work the same way. Mix them into water and pour directly at the base of the plant so it gets straight to the roots. Some powders are sprinkled around the base and watered in. Pellets are usually long lasting and slowly release nutrients over time as they’re watered.
Liquids tend to be the quickest acting. I know I keep talking about veg, but your ornamental plants might need a boost too. They won’t be giving you anything edible, but many like roses and dahlias are flowering right now. A feed with a higher potassium content will help them along nicely. Or you can mulch them with peat-free compost like I do and let nature do its thing.
I could go on about this topic and go even deeper into the science but I’ll stop here. I hope this gives you a bit of inspiration when it comes to fertilisers and feeding your plants. If you have any questions, email me at jamieslittleallotment@gmail.com
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