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Monday 5 June 2023 Dublin: 13°C
From the Garden How to make your own compost - you can learn from my mistakes
I have had some God-awful compost heaps over the years – slimey, smelly, sludgy yokes that festered away in the corner of the garden, writes Michael Kelly.

I DON’T ALWAYS get it right but every year I think I am getting a little better at making compost so that I can improve my soil and give my veggies the nutrients they need to grow.

The key I think is to treat your heap (or in my case, five heaps) not as a place where you can happily dump all manner of stuff from the kitchen and garden, but as if you were making a loaf of bread – you have to make sure you have the right mix of ingredients, bake it well and treat it with a little love.

I have had some God-awful compost heaps over the years – slimey, smelly, sludgy yokes that festered away in the corner of the garden. I had to avoid making eye contact with them each time I make a trip there.

The problem, I think, is that composting is always explained in a way that makes it sound highly technical. It’s all carbon and nitrogen ratios and one would think you need a PhD in Chemistry just to get involved. Any time anyone tried to explain the process of making compost to me, my eyes would glaze over and I would hear soothing music in my head while they talked.

So let’s get the science bit out of the way. Don’t be alarmed. In order for the material you’ve dumped into your heap to turn in to compost, there has to be a mixture of nitrogen and carbon.

So forget the word ‘ratio’ – it’s simply a fifty/fifty split, and it doesn’t need to be too precise. The green stuff in the heap is high in nitrogen while the brown stuff is high in carbon (see tip below).

If you have a good mix of both, you will have the right balance and it will break down and turn in to compost quickly. Too much green and you will get a really wet, sludgy heap like many of my efforts over the years  -the result of adding too much grass clippings. Too much brown and you get a really dry heap that won’t rot quickly (but will rot eventually).

How long it takes to turn to compost depends on what’s in it – could be 4-6 months but you will know when it’s ready by the fact that you have a nice crumbly compost with no smell.

I like the idea of closing the gate on fertility – in other words, making enough compost so that you don’t need to bring any fertilisers, compost or manures into your garden from outside. In reality, I am a little ways off that.

You will get approximately 20-30 wheelbarrows of compost from each heap you make. That sounds a lot, but each spring you will need a wheelbarrow of compost for each square yard of veggie bed.

The Basics: Top Tips for Composting

The smaller the materials and the layers you put on the heap, the quicker it will break down. Think of it as your own digestive system – if you chew your bread it will be easy for your stomach to break down. If you swallow it whole, it won’t.

So as a rule of thumb, chopping the materials with clippers will help. And, if you have bigger items like stalks of cabbages etc, bash them up with a sledgehammer first.

After that, the key is layering. Spread the layers out – don’t leave it all in a big mound!

Add about a 3-inch layer of brown material and then a 3-inch layer of green material on top until you get a heap that’s about 4-5 foot tall and then leave it alone to rot down – don’t add anything else to it.

That means you probably need a minimum of two heaps. In practical terms, I often have far more green materials than I have brown – I usually end up dumping some greens in a pile beside the heap and waiting until I have a brown layer before adding them.

It’s counter-intuitive, but regular turning (monthly) will aerate the heap, which will help it to decompose – the more often you turn it the quicker it will rot. A well-layered heap will heat up quickly, rot down fast and uniformly, it won’t smell and should be easy to turn.

The brown layer can consist of straw, wood ash, cardboard, newspaper, small twigs, leaf mould, soil or garden “sweepings”.

The green layer could contain seaweed, grass, hedge clippings and kitchen waste (veg only).

You can have a completely open heap, or construct sides for it with timber or timber pallets – this makes turning a little easier. It should be about 4ft wide and deep.

Start with a brown layer such as straw or twigs of at least 10 inches. Cover the materials with cardboard or old carpet to keep the worst of the weather off them.

Recipe of the Week: Carrot and Squash Soup

It’s January so let’s be honest, we need lots of detoxifying and frugal soups. This one is delicious and if you’re lucky, you may still have all the ingredients in your larder or garden to make it entirely homegrown.


  • 1 red onion, peeled and finely chopped
  • 2 cloves garlic, peeled and finely chopped
  • 2 tbsp olive oil
  • 4 large carrots, peeled and cubed
  • 1 medium squash, peeled, deseeded and cubed
  • Black pepper, freshly ground
  • 850 ml chicken or veg stock
  • 2-3 sprigs thyme
  • A handful of fresh parsley


Sweat the onion and garlic in the olive oil over medium heat in a large saucepan for about 5-7 minutes.

Add the carrots and butternut squash to the pan.

Season, then cover with a lid and cook for another 10 minutes on a low heat until the vegetables start to soften.

Pour in the stock, add the herbs and bring to the boil. Now turn down the heat a little, and simmer for about 30 minutes.

Finally, use a hand blender or liquidizer to purée the soup. Reheat and serve.

Michael Kelly is an author, broadcaster and founder of GIY.

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