How To Use Worm Castings To Make Your Plants THRIVE

If you're a lover of growing stuff and eating it, you're probably interested in making it as healthy as possible? Healthy plants make healthy peeps right? This article on how to use worm castings in your garden, on potted plants, and as a general fertilizer. How to increase the health of your soil, your plants, and ultimately, YOU.

I'm going to show you why building a worm farm is such a great, low cost venture which can make a big impact.

I'm going to excite and hopefully inspire you with tales of worm castings, what they are, and why they are such a valuable resource for the gardener. I'll be showing you a number of tips and tricks that you can apply to make your plants thrive.

For any gardener, whether new or experienced, the mad desire and  unrelenting passion to nurture seedlings into healthy, vigorous plants is exciting indeed.  And what makes plants thrive, be able to fend off pest predation and reach maturity?


Well, not just soil. As humans need nourishment to survive, so do plants. In an age where soil nutrient depletion is rife and the vitamin and mineral profile of soils are nowhere near where they were 50 years ago, the keen gardener needs to spend some time 'repleting' the soil in their own little piece of the planet.

Worm castings are in incredible soil amendment actually one of the most nutrient rich forms of fertilizer the gardener can use. A small amount can feed a houseplant for a number of months, can you believe that?

Worm composting enhances the ability of your soil to retain water, but also supporting adequate drainage. Yes, high quality organic matter supports both. It improves the texture of your soil over time.

The nutrients in worm castings are rapidly absorbed by plants and immediately available, unlike some other animal manures.

Tips on how to use worm castings with red wriggler compost worms showing in the soil

All seems like a lot of work and hassle? Well, it's really not. I found this little video and was actually really inspired by it. Just a normal gal in the city, sharing a flat with friends and tens of thousands of worms. Take a look...

What On Earth Are Worm Castings?

As you would expect, worm castings (also known as vermicompost, vermicast or just plain worm compost) are the waste products of worms. Yep, it's worm poop alright! The castings are packed full of a highly active mixture of bacteria, enzymes, plant matter and animal manure that is passed through the worm's body.

Worms are greedy critters. They eat their own body weight in organic matter every day. Imagine if we did that? That's a lot of burgers...

Cool er?

Back to the worm casting story. Water soluble plant nutrients such as copper, zinc, manganese, borax, iron, magnesium, potassium and calcium, just to name a few, are all found in worm casts. These essential nutrients are often not found in depleted soil, even in your garden.

As the organic matter moves through the worm it is coated in a layer of oil. This layer, which breaks down over a couple of months allows the nutrients to be immediately available, but slowly released over time. You end up with this soft, chocolatey, crumbly soil like humus that smells wonderful. It reminds me of the forest after a light spring shower, earthly, natural...sorry, I'm gonna cry πŸ™‚

If you are looking for a simple, economical and effective way to improve the quality of your soil and your plants, using worm castings as fertilizer is an excellent idea.

A small investment in a gaggle of worms (oh, that's geese isn't it?) is all that you need. Let's call them an 'army' for now. Each and every one of those slithering soldiers is going to go into combat for you every day. In camouflage of course!

You'll need to keep them in something of course. They don't make good pets just free-ranging around your house. But with a bought worm farm, or something you knock up at home, you'll be reducing your kitchen waste and building the rich soil additive that will have your plants tipping their hats to you.

Want to see worms going about their day jobs? This video of a worm farm is pretty incredible.

How Do I Produce This Magic Of Which You Talk?

Getting your won mini worm farm off the ground is simple. I talk about it here in my big guide to composting. Use the table of contents to scroll to the section if you don't want to read it all.

10 Funky Benefits Of Worm Castings

Worm castings have many benefits in addition to the ones I have mentioned already. Let's recap and add a few new ones you might not have considered:

  • Rich in  up to 60 nutrients and minerals that are easily absorbed by plants
  • Slow release so a small amount can nourish plants for a long time
  • Absorb and retain more moisture than normal garden soil
  • Aerate the soil and improve composition
  • Help extract toxins and harmful bacteria from the soil
  • Acts as buffer against high and low soil PH
  • Help reduce kitchen waste
  • Fun for kids to learn about worms and composting
  • Introduces healthy microbes to the soil
  • Cheap and easy to set up and maintain

I could go on, and on...and on. You get the gist? There really shouldn't be anyone who can't afford a worm farm. Other than the worms, which you might even be able go get for free if you ask around, the cost of setting this up can easily be ZERO. Nada, zilch, you can build a worm farm for free.

If you have $50 or so, you can but a bespoke one, but it's not essential. The worms don't mind whether they are in the Playboy mansion of worm farms (a lot of procreating goes on in a worm farm too)  or in a trailer style home.

Harvesting worm castings from a multi-tier vermicompost farm is easier, but even a plastic bin is fine to get started. Some people never upgrade.

As long as they are fed, kept warm enough, and are allowed a little adult fun with each other, they'll continue to provide you with fertilizer forever. Sounds a bit like humans er?

There really are no disadvantages to using worm castings in your garden. Just a little planning and setup and you're away!

3 tier worm compost farm showing full and empty sections

Multi-tied worm farms are great. They allow you to harvest your castings much more easily.

Uses Of Worm Castings Indoors And Out

Using Worm Castings In Potting Mix

Worm composted material can be mixed at a 50/50 ratio with your standard potting mix or even loamy garden soil. Ideally I like to put it all into a large plastic tub and use my hands or a small mini-fork to mix it in.

Use as normal potting mix, remembering to water in after repotting.

Worm Castings As A Soil Conditioner And Amendment

Using worm castings as a soil conditioner (soil amendment) is a great way to start. What you are basically doing is adding castings to the soil, mixing them together to combine the two.

You're certainly not going to have to do this to your entire garden bed, but when you dig a hole to plant a seedling or other plant, take a moment to mix equal parts worm compost to the soil, mix them together, replace around the plant and water in.

You can also do this in a bed that is currently empty before the planting season begins. This give the worm castings a chance to become one with the soil and enhance the nutrition and microbial content. Win - Win!!!

How To Use Worm Castings As Fertilizer

There are a couple of ways you can use your vermicompost as a direct fertilizer in the garden. Firstly, dig a hole where you are going to position a new plant. Place some of your worm poop (haha!) into the bottom of the hole and place the plant on top of it.

Backfill around the plant with the removed soil and bed in using your fist to remove air pockets.

The roots will have direct access to all the nutritional goodies. The roots will grow through the mix, out, and around it, but still be able to pull in the slow release nutrients that it provides.

An alternative for already established plants us to top dress around then. Try to avoid getting it onto the foliage, but taking a handful of castings and scattering them evenly around the periphery of the stem, watering in and leaving the goodness to soak down to the roots. This is a simple yet effective way to give your plants a superfood BOOST!

How To Use Worm Castings On Houseplants

House plants on a shelf

Use worm compost on your house plants to give them a new lease of life.

To reinvigorate house plants, make up a soil/potting mix and vermicompost blend, as we discussed in the soil conditioning section above. A 50/50 ratio is ideal, but you can use as low as a 25/75 ratio of castings to soil and still see good results. Repot and water in.

Top dressing house plants with your wormy magic is good too. As little as a tablespoon or two sprinkled around the base of the plant will give it the nutrients to get it growing well again. Water in and you're done.

How To Use Worm Castings In Your Garden

I've already discussed how you can enrich your soil by mixing it thoroughly with worm compost, or to use it when you dig a new hole for a plant. But what if you've already got the beds planted and you want to give this a shot? Here's how..

Side Dressing Your Vegetable Garden

Side dressing is a simple but effective way of adding fertilizer or soil amendments to an existing bed. Side dressing is particularly healthy for sandy soils that leech nutrients easily. The addition on humus rich material like casting can help improve the soil over time too.

Here are some of the vegetables that really get some benefit from this method:

  • Beets and beet greens
  • Brussel sprouts
  • Cabbages
  • Cauliflower
  • Lettuces
  • Kale
  • Eggplants (Aubergine)
  • Melons
  • Peppers
  • Celery
  • Potatoes
  • Cucumber

The list is pretty extensive. Most of the typical Northern hemisphere vegetables like a bit of side dressing (as opposed to cross-dressing, which is a whole different article!)

How To Side Dress With Worm Compost

Worm tea (see next section) can be used to side dress your veggie beds. You can also water your plants with it, but should use a slightly more diluted solution if you are going to water the leaves. 1/2 cup worm juice per 2 gallons of water is ideal for foliar watering, if you are just watering to the sites or base of the plant, you can half the water, thus doubling the strength of the solution. 

Pick one of these simple methods to apply the side dressing to your plants:

  • Add a small amount of the castings to the base of each plant, raking into the soil. I like one of those small 3-pronged mini-rakes for this. Water in. Alternatively,
  • Create a slight furrow down the side of each plant, or along a row. Sprinkle your fertilizer into the furrow and cover with soil. Water.
  • Alternatively, sprinkle some fertilizer over the whole bed when plants bear their first fruits. Water in as usual.

How To Use Worm Juice / Worm Castings Tea

Worm juice....errghh, yuk! Well, luckily we're no killing the worms and juicing them in the Vitamix. Worm juice is actually the waste products from the worms and the plant matter you have fed them, that bas broken down and collected at the bottom of you worm farm.

It's really just a byproduct of composting, and if you have a 2-tiered setup, the juice will collect in the bottom of the farm. Some purpose made worm farming bins will have a tap in the lowest tier so that the juice can be drained off.

Worm castings tea is some pretty potent stuff, so needs to be diluted on water before you use it. It can't really burn the plants, but aim for 1/2 to 3/4 of a cup of worm juice to 2 gallons of water.

Use this liquid gold to water around the root zone of your plants. It's incredible and you'll see your plants flourish quickly.

How To Store Worm VermiCompost

It's always nice to build up a little supply of your wormy compost, especially through the winter before the new growing season starts. Vermicompost can easily be stored until you are ready to begin using it.

When you first harvest your compost it is usually pretty wet. Not a good way to store it. Slightly damp is best, so you're going to have to dry it a little.

It's a good idea to harvest it onto a large square tub and leave it to dry a little, agitating and turning it with a small garden rake every so often to help the drying process.

The shallower the compost layer, the quicker it will dry out. You want it to get to the point that it's not wet, but will still clump together if you squeeze it in your hands.

Storage Containers

It's ok to use garden storage sacks for your castings, but 5 gallon plastic drums with some holes drilled in the lid work well too. Store this way and your compost begins to adapt to the aerobic environment. It can be stored for up to 3 years.

Never store in an airtight container as this will encourage anaerobic fermentation to take place which can be super stinky. Letting it dry a little and keeping airflow stops this problem.

Your Worm Castings Frequently Asked Questions

Where Can I Get Worm Castings?

It's possible to buy ready composted worm castings from many garden centers and a number of online stores. But making your own is easy, and I'd love you to try it before going out and buying ready prepared ones.

Compost worms can be purchased online and shipped in the mail. Aim to start a small worm farm with around 1000 red wrigglers. They propagate vigorously (dirty devils) and you'll be able to expand your operation pretty quickly.

It's also great to be able to give some away to friends, or even to your local school so the kids can learn about this incredible method of creating rich soil form kitchen scraps.

What Do Worm Castings Look Like?

Vermicompost in hands

Rich, fluffy, nutrient rich vermicompost ready to enhance the soil.

Worm castings look like rich, fluffy, aerated soil. 

Can Worm Castings Burn Plants?

No. Worm castings and worm juice are safe for plants. But if watering worm juice directly onto the foliage, it's definitely worth diluting it. It goes a lot further and gets to the entire plant. Worm juice is not produced in great amounts so use it in a watering can with water.

Are Worm Castings And Compost The Same Thing?

Nope. Although worm castings are often called worm compost, or vermicompost, they are not the same thing as you'd create on a common garden compost pile.

Both are created from organic matter, but there are definitely differences between them.

Compost created on your compost heap is essentially broken down into the gardener's 'black gold' by bacteria and fungi, although small insects and some worms do find their way in and help the process along. They break down the cell walls of the plants and eat the contained nutrients.

Worm compost on the other hand is passed through the worm's digestive system and pooped out the other end. These castings are much higher in humus content that garden compost. This is an awesome addition to soil as this higher humus content aerates the soil and allows it to retain more water, which in turn, allows your plants to send their roots down more easily, and be less stressed during dry times.

Compost is cool, it's excellent for the soil, and can be produced in much higher volumes that most domestic worm factories (farms). But worm poop wins in most departments, so a combination of the two types of compost is a good goal.

How Much Worm Castings Should I Add To The Soil

A 50/50 ratio is ideal if you are mixing it with soil/potting mix. If just adding it beds as a top dressing, a handful around each plant is usually sufficient.

Around pot plants, a couple of tablespoons will generally suffice.

Can I Worm Farm In Colder Climates?

Yes, you sure can, although you'll need to be able to moderate the temperature. Worms will die if left in sub-zero temperatures. A garage that is not too cold, or even an indoor worm farm are perfect in Northern climates where it gets cold.

I truly hope that this little expedition into all things worm poop related has been super informative and useful to you. I aim to please and share the tidbits I've learned over the years.

If you have anything to add to the conversation, however huge or small, leave a comment so we can learn this stuff together.

4 thoughts on “How To Use Worm Castings To Make Your Plants THRIVE”

  1. Hi Steve,

    This is a brilliant post! Super informative and really in depth. There is everything here for someone to get started with worm composting. Those videos were fun to watch too.

    How long have you been using worm compost for?

    Thank you for writing such a great post and for sharing your expertise with everyone .

    – Kevin

    • Hey Kevin

      Thanks so much for taking the time to comment, yeah, I loved those videos too πŸ™‚

      I started worm farming while I was living on Australia. I guess it was 2006 or so. Started with just some of those polystyrene fruit boxes that the greengrocer throws out, worked great for worms.

      I really like it, it’s a good way to get rid of the scraps, and pretty quick too. I also do some Bokashi composting indoors, which is quite cool too.

      Thanks for stopping by, love to get a comment from someone who has found my scribbling interesting.

      All the best


      • 2006? That must make you a worm composting pro!

        There is a food waste collection where I live, so it’s too easy to throw all scraps into the collection bin. I need to take some inspiration from you and start separating the things I can compost! I’ve never tried worm composting before, but I might just have to give it a go.

        No worries Steve, I always love stumbling across new blogs. I’ll be keeping an eye out for your new posts!

  2. I mixed 20% pure organic worm castings into a good quality organic veg & herb potting mix for my container peppers this season. Do you think my plants will have enough nutes for the entire season or should I be looking to add something later on in the season such as a water soluble fert?


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