27 April 2020

Make your own compost mix

Remembering the art of home composting to create your own potting mixtures.

By Richard Gianfrancesco


You’ve probably noticed green waste council collections being cancelled and supplies of potting compost severely restricted due to garden centre closures.

So, the art of home composting and making your own potting mixtures is a handy skill to have in your back pocket.

Start now and in three to six months’ time, you’ll have great compost to work with.

Compost © RBG Kew
Compost being made in the Stable Yard at Kew Gardens
Compost being made in the Stable Yard at Kew Gardens, Ellen McHale © RBG Kew

Sustainability of home recycling

It’s always been the most sustainable practice – to compost your own garden and kitchen waste.

But in the last few years, local councils have been increasing their bin collections to include all food waste – both cooked and uncooked, as well as all garden waste.

We’re getting into the habit of chucking it all in the ‘brown bin’.

But if you have your own garden space, there are things you can do at home to recycle.

Composting at Kew

Here at Kew, we make our compost on a slightly larger scale.

Each year, 3,500 tonnes of prunings and clippings gets mixed with over 2,500 cubic metres of stable bedding supplied by the Royal Horse Artillary Barracks.

With a quick shred and regular turning, in just 10 weeks this compost is ready to be returned to the Gardens, used mainly to mulch our beds.

Plant waste to be composted at Wakehurst
Plant waste to be composted at Wakehurst © RBG Kew/Ellen McHale

What you will need:

  • From the kitchen: Essentially any uncooked fruit and vegetables including teabags and eggshells can be added to your heap. No meat, dairy or cooked veggies.
  • From the garden: Grass clippings and soft young weeds are great ingredients to add, but if your heap just contained kitchen scraps and grass clippings it would soon turn into a slimy, smelly heap.

To stop this from happening, you’ll need to mix this ‘green’ waste with other 'brown' materials from your home and garden.

  • Prunings (provided they’re chopped up small) and fallen leaves are ideal.
  • Cardboard is great to counteract greens, as is old bedding from herbivorous pets such as rabbits and guinea pigs, as well as straw, shredded newspaper and even natural fabrics such as cotton.
Compost being made in the Stable Yard at Kew Gardens
Compost being made in the Stable Yard at Kew Gardens, Ellen McHale © RBG Kew

Where to put your mix:

First, make your pile directly onto the soil – if you don’t, it will be much harder for the worms to find it.

It’s also best to use a bin – a plastic, dalek-style bin is ideal for a small garden, but if you don’t have one, you can make your own – out of an old upturned dustbin.

If you have a larger garden, try making an enclosure of around a square metre out of old pallets or pieces of wood.

Research has shown that material in enclosed bins heats up and composts more quickly, but even an open pile will compost eventually.

Keep the whole compost heap moist to make it uninviting for unwanted creatures or invest in a fully enclosed plastic bin.

Hands in soil
Hands in soil/Unsplash

Make your compost

Try to start off with some twiggy material or corrugated cardboard at the base – anything that will help to encourage airflow through the heap.

Then build up in layers – food waste, grass clippings and other leafy green material go in one layer.

Then, like building a lasagne, add lots of thin layers; more carbon rich, ‘brown’ materials such as leaves and twiggy material or straw, shredded newspaper, or cardboard.

If you have the energy, it's worth mixing the heap by moving the outside material to the inside every few weeks.

Top tip: If it’s dry give it a water too.

In no more than six months you should have perfect compost for the garden borders, veg plot or even to use as an ingredient in potting compost.

London Plane tree at the end of the Broad Walk at Kew Gardens
London Plane (Platanus x hispanica) © RBG Kew

Making your own potting compost

You’ll only need garden soil, garden compost and leaf mould; all supplied from your own garden.

  1. Leaf mould: Mow over fallen leaves in autumn to chop them finely. Add them to black bin bags and water or a leaf-only compost bin; in 12 months you’ll have beautiful, moisture-retentive, consistently low nutrient material.
  2. Garden compost: Follow the advice above and within six months your kitchen and garden waste will have turned into organically rich, crumbly, dark compost.
  3. To bulk these materials out further, and to give some weight for tall plants in containers, you’ll need some soil. If by chance you have a well composted loam stack, then this will be ideal. However, for most of us, we’ll need to beg and borrow bits of soil from the corners of the garden and veg plots.

To get rid of stones, lumps and twigs, it’s worth sieving all of these, then you’re ready to make your mixes.


The best material to use for seeds is sieved leaf mould. It's finely textured, low in nutrients and moisture retentive. If you don’t have enough to last you can mix up to 50% sieved soil.

Potting on

Young plants are more vigorous and need more nutrients to give them a good start. However, the mix still needs to be moisture-retentive, light and airy to encourage good root growth.

Here, the ideal mix is around 1/3 sieved leaf mould, 1/3 sieved garden compost and 1/3 sieved soil, all mixed together.


By this stage, plants should be well established and be ready to ‘rough it’.

100% soil mixes in containers can be too heavy and the soil can become compacted, so mixing in around 50% sieved garden compost will lighten the mix, increase moisture retention and increase available nutrients.

The nutrients contained won’t last the whole summer so don’t forget to feed, either by adding a slow release fertiliser now, or a liquid feed later in the summer.

These mixes are all ideal for flowers and veg, and in this period of getting back to nature, once in the habit you can leave the compost in the garden for years to come too.

A selection of items from the Temperate House collection

Shop at Kew

From books for beginners to tools for enthusiasts, our online shop has something for everyone.

Read & watch