Complete Guide to Using Worm Castings in Your Garden

Learning how to use worm castings in your garden can deliver that elusive piece of the puzzle to take your plants and soil to the next level. Discover the different applications of castings in your gardening adventures.

How to Use Worm Castings

Once you begin using worm castings in your gardening, you’ll ask yourself what took you so long to discover this black gold.

where have you been my whole life
credit: yarn

When you see your plant’s response to this magical substance, your mind will start to race with how else you can use it in your garden. And here is the answer to that question – how to use worm castings in your garden.

What is Worm Castings Good For?

In this guide, we will be exploring the following ways to use worm castings:

  • Worm compost tea,
  • seedlings,
  • improve soil quality,
  • hanging baskets,
  • vegetable garden booster,
  • stress reduction,
  • lawn, and
  • much more.

It may sound cliche, but the possibilities are only limited to your imagination.

Okay, as you can probably tell, we are excited about this subject, so let’s jump in.

Guide to How to Use Worm Castings in the Garden Outdoors

To be honest, there isn’t any wrong way to use worm castings (or vermicompost) in your gardening endeavors. However, it can be challenging to devise ways to use this black gold goodness in your plants.

We’ve put together a list of ways to apply worm castings to your garden in the hope it provides some inspiration.

Using Worm Castings to Revitalize Old Soil

worms in the garden

One of our favorite ways of introducing all the goodness of worm castings to our plants is by rejuvenating old and tired soil.

When soil becomes old and too dry, it can become hydrophobic (repels water). You will see this happening when you water your plants, and the water sits on top of the soil rather than absorbed into the ground. You may also notice some cracks forming in the soil due to it becoming hard and solid.

Not only does this cause the water to flow away from the plants, but the rock-hard soil also prevents oxygen from reaching the root systems.

Introducing worm castings will immediately inject some life back into the soil.

Worm castings will deliver water absorption properties and aerate the soil. In addition, the simple act of breaking up the soil while you mix in the worm castings will also help oxygen reach the roots.

To revitalize old soil, we recommend the following steps:

  1. get your hands dirty and begin breaking apart the old soil in a container,
  2. grab a handful of slow-releasing fertilizer and sprinkle it liberally into the soil (even though worm castings contain good nutrients, it is not in high concentrations. Read more about worm castings and why we recommend adding fertilizer HERE),
  3. mix in fresh worm castings into the soil until it is evenly distributed (we’ll discuss the amount of worm castings below), and
  4. return the refreshed soil from where you got it.

How Much Worm Castings to Use

How much worm castings to add to the soil depends on how much soil you try to reinvigorate!

  • If you are trying to spruce up some old ground soil, a good worm casting to soil ratio is 1/2 cup of worm castings for a square foot of soil.
  • If you apply it directly to the soil (top dressing) around plants, we recommend evenly spreading 1-2 cups of pure worm castings per mature plant.
  • If mixing soil and worm castings in a container, a good worm casting to soil ratio is 1:4.

How to Use Worm Castings in Vegetable Garden

Speaking of refreshing soil, a great place to put this into practice is in your vegetable garden or patch.

When it comes to feeding with commercial fertilizers, one of the main concerns is putting in too much, leaving excess fertilizer to collect in the soil. If fertilizer chemicals remain in the soil for too long, it becomes toxic, which can detrimentally impact your vegetable plant health and production.

The great thing about worm castings is it is impossible to overdo it.

This makes sense. Otherwise, worms in the wild would wreak havoc.

With that in mind, we highly recommend using worm castings in your vegetable gardens and spreading the black gold love.

There are several ways to use worm castings in your vegetable garden. Such as

  • creating worm castings tea to use as a liquid fertilizer to spray all over your plants. To do this, mix 2-3 cups of worm castings in water (1 gallon). You don’t have to worry about burning the foliage because it is an organic worm-casting fertilizer.
  • Worm castings seed starting – the humus feel, lightness, and excellent aeration properties make worm castings an ideal seedling starter when you initially plant your vegetable seeds. Mix a 1/4 cup of fresh worm castings into the soil you use for your seeds.

How to Use Worm Castings in Raised Beds

The applications that you use worm castings in vegetable gardens can be applied to raised garden beds too.

Introducing worm castings to your raised beds has a three-fold effect.

  1. Worm castings provide an instant nutrient boost,
  2. It improves soil quality through the aeration of organic materials and
  3. helps to cultivate the soil’s natural micro and macrofauna population.

We like to take it one step further and install a worm farm tower in our raised garden beds. Like when we installed two worm farm towers in our triple-layered raised garden bed.

You can read about how we constructed it in our tutorial HERE.

This way, you can increase the worm population directly in your raised garden bed. And keep them well-fed with kitchen scraps in the worm farm towers.

Using Worm Castings on Lawn

We love to apply worm castings to our lawn to give it a quick injection of nutrients and minerals.

It is a light fertilizer that can give your lawn a quick boost of nutrients between your regular lawn fertilizing schedule.

It is possible to use fresh worm castings on your lawn. However, we find the high moisture content of fresh castings can make them clump and become a messy exercise.

We prefer to let the worm castings dry, allowing us to granulate the worm poop into a powder. The granulated castings are much easier to spread across a lawn, achieving an even spread with a lawn fertilizer spreader or a hard-bristled broom.

Another benefit of using worm castings on your lawn is that you don’t have to worry about burning your beautiful grass. Worm castings do not contain concentrated chemicals like synthetic fertilizers – which can cause your lawn to suffer from fertilizer burn and create unsightly patches.

How to use Worm Castings on Houseplants

You’ve seen how versatile worm castings can be outside in the garden. Let’s now consider how worm castings can be used indoors.

How to Use Worm Castings in Potted Plants

Like tired soil in the garden outside, worm castings are a great way to refresh old soil in container plants.

Whenever we get the opportunity, we like to include 1/2 cup of fresh worm castings in the soil we use to repot our houseplants.

Apart from the benefits, we discussed earlier, like providing a nutrient boost to the soil and improving water retention and aeration. The castings also provide a not-so-obvious benefit during the transplanting process – stress reduction. We look at this in more detail in the next section.

Stress Reduction in Transplanting

Using worm castings during the repotting or transplanting process significantly helps to reduce the shock or stress plants experience.

The additional nutrients released by the worm castings stimulate the indoor plant’s root development response. This helps the plant to quickly begin new root growth and establish a foothold in its new home.

This also works well during seedling transplanting. Adding a teaspoon of worm castings into the new potting mix planting hole you are transferring your delicate seedlings will give them that extra spurt they need to grow and establish their root system quickly.

Top Dressing with Worm Castings for Indoor Plants

One of the simplest ways to use worm castings for indoor plants is to apply them as a top dressing.

And we’ll put our hands up and admit we use this method when we feel a bit lazy on any given day.

To top dress indoor plants, start by liberally sprinkling a 1/2-inch deep layer of worm castings on the surface of your potted plants’ soil. All the black gold goodness will slowly move down towards the roots system each time you water your plants.

how much worm castings to use

Hanging Baskets

The same can be applied to plants in hanging baskets.

We frequently use the top dressing method to give our hanging plants a quick feed. Simply grab a handful of worm castings and sprinkle them on top of the soil for an instant boost.

Alternatively, mix some worm castings into the soil during the repotting process.

Frequently Asked Questions – How to Use Worm Castings

How much worm castings per gallon of soil?

When you purchase a mature tree or shrub, it often comes in gallon bags of soil to sustain the roots. So an excellent measurement to reserve in your gardening knowledge bank is how much worm castings you should mix into a gallon of soil.

We recommend a ratio of 1 to 1 1/2 cups of worm castings to a gallon of soil.

Make sure to mix the worm castings evenly through the soil.

How often should I use worm castings?

Firstly, let us say you can’t really overuse worm castings with your soil.

At the same time, you don’t want to constantly harvest worm castings every week.

So what is a good balance for the frequency of applying worm castings to your indoor plants and garden?

We generally mix in worm castings once every 2 months for indoor plants. And we are increasing it to once every month during the peak growing periods.

For our garden outdoors, we like to top dress once every 2 weeks during spring and summer. And we drop the frequency down to once every 4 weeks during the colder months.

Why are worm castings good for plants?

Besides the fact that worm castings are packed full of nutrients and minerals essential for healthy plant growth. Worm castings also improve help to improve the soil’s properties that facilitate optimal growth, such as increasing the water-retaining properties of soil, improving the aeration of soil allowing oxygen to reach the roots, and feeding and fostering a vibrant microorganism culture.

Do worm castings help during flowering?

Yes – worm castings contain various essential nutrients for plants, including the element responsible for a plant’s reproductive organs, phosphorus. This means adding worm castings just before and during flowering will assist your plants in producing a complete and burgeoning bloom.



  • Vermicompost. (2022, October 31). In Wikipedia.