How to Make a Budget-Friendly Worm Castings Farm

Worm castings are one of the most nutritious fertilizers you can feed to your garden. It is easy to observe gardens that have a rich tapestry of microorganisms in their soil, because the plants look fuller, happier and rich in blooms and fruit. The good news is you can harness the power of worm castings by learning how to make worm castings farms.

Making a worm castings farm isn’t as hard as you think. It involves building up layers of organic materials, such as newspapers, food scraps, and vegetation from your garden in a container. Then introduce particular varieties of worms into your farm, to facilitate the decomposing process of organic materials into beautiful, rich worm castings for your garden.

How to Make Worm Castings Farm

Today at the Garden Bench Top, we are going to get down and dirty with our friends, the worm. You may have initially found them slimy, wriggly and a huge turn-off. But as you progress further down your gardening journey, and learn how they enrich your garden, you’ll come to appreciate them. You may even find yourself giving stray worms a helping hand by carrying them into your garden beds. We know we have!

So get a wriggle on, because we have some learning to do about how to farm worm castings.

What are Worm Castings?

worm castings in a box
credit: reddit

Before we get into the DIY portion of this article, let’s familiarize ourselves with some terminology. What exactly are worm castings?

Worm castings are a nice way of saying worm poo!

There’s no sugar coating it for you – we are farming worm feces. And we couldn’t be more excited about it. Poo has a stigma attached to it, that is generally taboo and disgusting. But not worm poo. Once you see the impact worm poo has on your garden, we guarantee you’ll have a change of heart.

As worms work their way through decomposing organic matter, they produce a material called vermicast, or worm castings. It is these worm castings that are a form of enriched soil, and consist of processed organic matter ready to be absorbed by the roots of the plants above.

If you ever wanted to look for worm castings in your new worm castings farm, they look like miniature football – shaped bits of soil chained together or in clumps.

How to Make Worm Castings Farm – Budget Friendly

Okay – now you’ve had an opportunity to get your head around the fact that we are farming poo, let’s get into the DIY nuts and bolts of making a worm castings farm.

styrofoam worm castings farm
credit: pinterest

What You Will Need:

Before we begin, you’ll need the following materials:

  • Live Compost Worms (you can source these from around your garden, however generally the commercial products generally have eggs and other beneficial materials that speed up the process)
  • soft organic materials like straw or fallen leaves from the garden
  • compost and soil mixture sourced from your garden
  • food scraps sourced from the kitchen
  • large styrofoam box – must have lid (IMPORTANT to keep out pests)
  • hose piece – approximately 2-3 inches
  • sharp knife
  • gravel or pebbles
  • cloth (we like to use a hessian material that is absorbent)

STEP – Prepare Your Styrofoam Box

The first step is to install a drain into your styrofoam box. The reason we are installing a drain is to prevent the build up of moisture and water at the bottom of the worm castings farm. If too much water pools at the bottom of your farm, the worms can drown, and you will end up with a soup rather than rich worm casting fertilizer.

To install a drain, grab your hose piece and push the end firmly against one end of the styrofoam box, approximately 1 inch from the bottom. This will leave an imprint for you to work with.

STEP – Cut the Drainage Hole and Insert Hose Piece

Grab your sharp knife and carefully work your way through the side of the styrofoam box to create a hole slightly smaller than the hose imprint. We want the hose piece to fit snugly into the hole (as opposed to a loose fitting). Remember, you can always make a hole bigger, but making it smaller requires a bit more time and effort.

Insert your hose piece and adjust accordingly until it is fitting nicely into the hole.

STEP – Lay the Gravel and Cover with Material

The next step is to lay a foundation of gravel at the bottom of your box. It should be approximately 1 inch deep, or level with the hole in the side of the box. Once you have evened out the layer of gravel at the bottom of the box, cover it with your material.

The material should allow water to drain down into the pebbles, while also preventing any worms from falling down into the pooled water.

STEP – Layer Organic Materials and Worms

Now comes the fun part – filling your styrofoam box.

Begin by laying a foundation of compost or garden soil on top of the fabric. We like to include a mixture here, so the worms have a variety of materials to work their way through.

Next lay some organic materials like fallen leaves or straw on the compost/soil mixture. Make sure not to include any grass clippings in the mix, as it can lead to unwanted weeds in your garden beds.

Now it’s time to introduce the stars of the show – your worms. Spread them out evenly over the other layers. If you have another worm castings farm or have access to worm castings, now is the time to add it. Worm castings will have plenty of worm eggs to get your worm colony growing.

We like to add a sprinkling of food scraps on top of the worms to get them going. But don’t overwhelm them – the worms won’t be able to eat it all, and it will rot instead of becoming worm food.

Finally, finish the layering with a moist layer of straw.

STEP – Water Your Castings Farm

Now it’s time to water in your worms and tuck them away. Give your worm castings farm a healthy watering (any excess will drain away).

Once you have given them a drink, cover the farm with a secure lid and place the farm in a shady part of the garden.

How to Make Worm Castings Farm – After Care and Maintenance

worm castings farm

There you have it, your very own worm castings farm.

Leave your farm for a few weeks to give your worms a chance to settle in and begin processing the materials.

Then you can begin to feed the farm food scraps from your kitchen. Once your worm colony grows, it will get to a point where you can’t keep up with them! This is a good thing.

Also remember to give your worm farm a good watering every couple of weeks. Use the excess water that drains from the farm to water your garden. It is actually called worm wee, and it is full of nutrients your plants would love to soak up.

What are the Benefits of Worm Castings?

Okay – so we know we are farming worm castings – but do you really know the reasons why they are so beneficial for your garden?

Here’s a rundown for you.


In your farm, the worms have processed the organic materials through their system, and essentially tunneled their way through the delicious food. This effectively breaks down the organic matter that you harvest, leaving you with wonderfully aerated soil that helps the roots of your plant receive the necessary oxygen they need to survive.


If you notice the population in your worm farm beginning to explode, transfer some worms into your garden to help aerate the ground soil.

Nutrient Rich

A study by the University of California found that worm castings are rich 100% organic humus. They said they contain:

iron, sulfur, calcium, nitrogen, phosphorus and potassium (NPK rating: 5.5. 3). They are much richer in nutrients than bulk compost, therefore application rates are much lower. Chemical fertilizers are a one-shot wonder.

University of California

Essentially, this means you only need a small amount of worm castings to provide the same amount of nutritional benefit to your plants, compared to compost and other chemical fertilizers available at your local nursery and garden shops.


Another benefit (and our personal favorite at the Garden Bench Top) is that learning how to make worm castings farms is an eco-friendly skill. We sincerely believe every household should have one, even the ones without gardens.

Rather than throwing your kitchen scraps into the trash and filling up the landfills around the world, we can turn them into usable materials that help plants to grow.

And we don’t have to tell you, the more plants around the world, the cleaner our air and healthier the planet becomes.

It just makes sense!

Frequently Asked Questions – How to Make Worm Castings Farm

How Much Worm Castings Can a Worm Farm Make?

Now that you have a new-found passion for worm casting farms, it’s natural to wonder how many casting can a worm farm produce.

A paper by J. Fong and P. Hewitt from the Institute of Cornell estimated that two thousand red worms in a worm bin (farm) can produce 7 pounds of castings in one month.

7 pounds doesn’t sound like much, but when you realize that you only need a small amount of castings for each plant (literally only a teaspoon full), you soon see that it goes a very long way. And that’s each month!

How Soon Can I use Worm Castings from Worm Farm?

Worm castings are a valuable resource that can be used in many ways.

We like to take a teaspoon full and place it at the bottom of our garden plants. They will not only fertilize our plants, but there are thousands of worm eggs in the castings. Which in time will help to build up the health of our garden’s soil with beneficial fauna, producing healthy soil.

We also like to take a teaspoon full of castings and mix it with water in a watering can. The diluted form of worm castings essentially becomes worm tea, or a natural fertilizer, and provides the same nutritional value as castings – only in liquid form! This is great to use for potted plants and indoor plants.