How much worm castings to add to soil?

How to Use Worm Castings in Your Garden

Feeding your garden organic, powerful nutrients is the key to productivity!

One of the keys to a healthy, productive garden is to feed your plants and garden soil powerful, organic nutrients on a regular basis.

Over the next few weeks, I’ll be sharing all about “Feeding Your Garden”, in a series of blog posts and YouTube videos. This series is will be about four of my favorite, tested, go to products that I use to feed my garden: worm castings, worm tea, my favorite organic fertilizer, and, of course, compost. These products help my garden be healthy, productive and grow lots of food for my family to eat and share with others.

We all know how amazing worms are for our gardens. Earthworm castings and earthworm tea (covered in the next post) are produced by worms and are very beneficial for the long term plant and soil health of our gardens.

Earthworm castings are organic, and are a powerful soil enhancement. In this post, we’re going to talk about what worm castings are, why they are beneficial to our gardens, and how to use them.

What Are Worm Castings?

Simply put, worm castings are worm manure, or worm poop. Unlike cow or horse manure, they don’t smell. In fact, they are very earthy smelling, safe for the environment, and safe to use around your family and pets

Why are Worm Castings Beneficial for Our Gardens?

VermisTerra Worm Castings – “Black Gold”

1. More than just NPK

Worm castings supply so much more than just the nitrogen, phosphorus and potassium (NPK) that you see on bags of garden fertilizer. They also supply elements, trace minerals and natural growth hormones that are critical to optimal plant growth.

In addition, worm castings are high in humic acid. Humic acid frees up nutrients in the soil, making these nutrients readily available to your garden veggies. This makes worm castings more powerful than animal manures and synthetic fertilizers – which must be broken down in the soil before the plants can absorb the nutrients.

2. Rich in Beneficial Bacteria and Microbes

Beneficial bacteria and microbes are microscopic organisms that are added by the worm in it’s digestive process and are very active in worm castings. The microbes and beneficial bacteria help create a healthy, living soil. They live around the roots of the plant, protecting them – making them healthy and strong – and provide the perfect atmosphere for vigorous plant growth.

3. Support Against Pests and Disease

The army of good microbes in the worm castings protect the roots of your plants. Healthy plants are able to defend themselves against pests and disease, while weak plants emit a wavelength that attracts pests and disease.

Over the years, I’ve made my own castings with a DIY worm bin and purchased bags of castings at a local garden center. However, for several months now, I have been using VermisTerra organic earthworm castings regularly in my garden. They are quick and simple to use, a little goes a LONG way, and the results I am seeing are pretty impressive!

Mindy and CaliKim

VermisTerra’s Story

VermisTerra is a Southern California family owned business. Because they are located nearby, I had the opportunity to meet the family personally. As I got to know them, not only was I deeply touched by their family’s story, but realized that they take great care to make sure their worm castings and worm tea are of the highest quality.

Their expert, Mindy, paid several visits to my garden. During her visits, she shared with me that her dad, grandfather and uncle ran a veggie farm for 20 years. They used conventional methods with chemical fertilizers. When Mindy was in college, her dad and grandfather contracted cancer, and although they fought hard to overcome the disease, they didn’t make it.

After their deaths, her uncle switched to farming with organic methods, and then decided to start a worm farm in 2002. Because of their personal tradgedy, Mindy and her uncle became passionate about teaching people how to grow their own food organically. Though their worm farm, they began producing high quality worm castings and worm tea that are safe for people to use on their gardens.

What Makes VermisTerra Worm Castings Special?

A garden’s best friend…

VermisTerra worms are fed green waste – using no animal manure or fillers like newspaper or cardboard. The castings are then aged 7-10 years, and screened, making them a super fine texture, and easy for plants to absorb. Many people think the fresher worm castings are, the better. Quite the opposite! When worm castings are fresh, they contain undigested material that is still decomposing, and the plants are not able to absorb the nutrients in the castings.

VermisTerra is certified organic by the USDA, and the California CDFA. They test each batch of castings (something very unusual in the industry) to make sure they are of the highest quality, and contain no heavy metals or toxins.

VermisTerra’s worm castings truly are “black gold” for your garden!

How to use Worm Castings in your Garden

Worm castings are very easy to incorporate into your regular garden feeding routine. The key is: keep it simple, and little goes a very long way.

Worm castings help with germination when starting seeds.

Starting Seeds

Worm castings are especially effective for starting seeds indoors or out, because they protect the roots of the seedings, help prevent damping off disease, and keep fungus gnats under control.


-Use a soilless mix of 2 parts coco coir (more on this in video below) and 1 part worm castings, OR

-Add worm castings to your bagged potting soil, 2 parts potting soil to 1 part worm castings.

-Place your potting mix/soiless mix in small seed cells, a cup, or other small container.

-Plant your seeds.

Container Plants

Worm castings are timed release, so work well in container gardening.

Worm castings are effective for containers plants because they are time released (thus only need to be used once a season) and don’t burn the plants.


-Put 1-3 tablespoons around the base of your container plants

-Scratch into the surface

-Water in with worm tea – castings and worm tea are a perfect team! (More on this in my next blog post.)

Garden Beds

Using worm castings in your garden beds will increase the survival rate of your transplants, creates aeration, and makes your soil healthier. Soon you’ll see more worms in your garden beds – they will leave their own castings. Over time, you will need to add less and less castings as your soil becomes a healthy, living environment for your plants.


-Sprinkle 1-3 tablespoons into the planting hole directly, OR

-Use 1 pound per square foot when amending your entire garden bed.

-Water with worm tea.

Watch the video on my YouTube channel below “How to Use Worm Castings in Your Garden”, to see exactly how to use them, and to enter a drawing for free worm castings. Watch today – entry deadline is February 15th, 2017!

To purchase VermisTerra worm castings or tea, click on the “Partner’s Store” tab at the top of this page, use promo code “calikim” for 10% off. Receive free shipping for any orders over $55. For a limited time, they are offering a free quart of worm tea (a $26.99 value) with any purchase, so you can try it out for yourself!

I’m seeing fantastic results with using VermisTerra’s‘s worm castings in my seedlings, container plants and garden beds. My winter garden this year has been very healthy and one of the most productive I’ve ever had!

Have you ever used worm castings in your garden? Comment below and let me know!

Thanks to VermisTerra for providing worm castings to test in my garden and for sponsoring this blog post. Some of the links in this post are affiliate links – I make a small commission when you order through these links and its helps me keep the garden content coming!

My eBook * My Garden Coloring Book * My Amazon Garden Store Front

You can follow me, view how-to videos, photos of my garden, and lots of growing tips and tricks, on YouTube, Instagram, Facebook, and Pinterest

166 Wilson Road,
Middle Swan


The short answer is ‘anything that was once living’. However, meat and bread isn’t great to put in a worm farm as it will attract rodents and be quite smelly.

Best to stick to material like:

  • Vegie peelings and scraps (small scraps break down faster)
  • Leftover cooked vegetables are fine too
  • Hair – human or pet
  • Dust (empty your vacuum cleaner into a worm farm!)
  • Garden waste (although large pieces won’t break down quick enough.) Shredded material or leaves is OK.
  • Lawn clippings (in small amounts are fine.)
  • Damp shredded paper, newspaper and cardboard
  • Cloth – natural fibres like cotton, linen, wool, hessian
  • Coffee grinds, tea leaves and tea bags
  • Egg shells (crushed is best.)

Animal droppings CAN be disposed of in a worm farm but there are things to consider:

  • If pets have been recently wormed, this will kill off your worms in the worm farm.
  • Pet faeces can contain harmful bacteria. Don’t use product from a worm farm fed pet droppings on vegetable crops. (It’s fine for flowering ornamentals and general garden plants).
  • Don’t over feed worms on pet poop. If the ratio of animal droppings to worms is wrong, you will have excess poop breeding flies and generally going nasty!

Some people keep a worm farm specifically for pet droppings, as they find it easier to manage as a separate entity.

Monitor your worm farm to ensure you don’t over feed worms.

If your worm farm is rank and smelly, cut back on feeding for a while and monitor how much food the worms are getting through.

A sprinkling of dolomite once a week over the surface is also beneficial to ensure conditions do not become too acidic.


Once your worm farm has been operating for at least a few months or more, you may wish to harvest castings, or remove some of the worms to use elsewhere.

The easiest way to do this is by using light, as worms will always go deeper to try and remain in the dark.

You can simply remove the lid from the worm farm for about an hour and remove castings from the top layer. The worms will be hiding deeper so you shouldn’t be collecting too many.

Or, if it is the worms you wish to harvest, there are a couple of methods you can try.

Worms love high protein, fine cereals like pollard (used as burley by fishermen). If you sprinkle a light layer of this on top of your worm farm for a couple of days, you should find the worms will be close to the surface, and you can scoop them out.

Or another way is to spread the castings out over a piece of corrugated iron, and leave it for about half an hour. Worms will go as deep as possible into the corrugated spaces, meaning you can sweep the castings off the top, then collect worms from each downward row of corrugations.


Worm castings are full of beneficial soil microbes that will help your plants grow, and access nutrients. Castings will also contain worm eggs (that will hatch and give you more worms!), and castings are naturally very water absorbant.

They are ideal to use incorporated into seed raising mix and potting mix, or use a handful in planting holes with young plants or seedlings. It is always best to incorporate castings into the soil rather than leave them on top – once they dry out, they can be very water repellent and also you lose the wonderful benefits of microbial activity in the castings (soil microbes need moisture to live – just like us!).

Try steeping a cup of castings in a bucket of water. Allow to steep for a day then drain off the liquid to use as a liquid tonic for your garden.

More information on keeping live worms can be found in this .

Hello –

A sort of super compost, worm castings are rich in nutrients and loaded with the microorganisms that create and maintain healthy soil. The beneficial microbes aid plant growth, help fight off disease and nourish your plants with readily absorbed nutrients that keep them healthy and productive. Clemson University Extension lists the following benefits of worm castings.

• provides nutrients to the soil
• improves the aeration and internal drainage of heavy clay soils
• provides numerous beneficial bacteria
• improves the soil structure’
• increases the soil’s ability to hold nutrients in a plant-available form
• increases the water holding ability of sandy soils

Because vermicompost is usually made in modest quantities, it is often used as a top or side dressing for potted plants. Mixed with regular compost it adds a boost to garden soil. Blended with potting soil, it invigorates plants growing in containers, inside or out. Castings contain 4% to 5% nitrogen in a slow release form and should not burn plants when properly used.

Gardens: Apply 5-10 pounds per 100 square feet and work into the soil.

Top Dressing: Simply spread a layer (about 1/2 inch deep) around your favorite plants. Mulch and water thoroughly.

Potting Mix: Add one part vermicompost with two parts compost, and 3/4 part vermiculite, perlite or coconut coir. Mix 1 Tbsp all-purpose fertilizer per gallon of soil.

Shrubs & Trees: In late spring, mulch around plants with a 1-4 inch thick layer.

Hope it helps!

All You Need to Know About Earthworm Castings

Earthworms benefit gardens in many ways as they move through soil creating spaces for air and water. But they also leave behind less familiar contributions — their castings. Earthworm castings, the end-products of worm digestion, are so useful some gardeners raise their own worms just to maintain a good supply of them.

What Castings Bring To Soil

Earthworm castings are full of organic matter and desirable microorganisms that yield benefits far beyond what fertilizer ratios show. Earthworm castings contain low levels of essential plant nutrients, including iron, that are guaranteed not to cause fertilizer burn. The dark brown granules don’t hint at their origins — their rich, earthy texture reminiscent of fine garden compost or dry coffee grounds.

Added to soil or potting mixes, the organic matter in castings improves soil structure. With more humus than traditional compost or normal garden soil, castings increase the water retention in soil, improve soil aeration and anchor plant nutrients that would otherwise leach away with water. Organic matter feeds soil microorganisms that produce, store and slowly release plant nutrition. Earthworm castings suit all indoor and outdoor gardens.

How Castings Benefit Plants

Earthworm castings provide substances that directly influence healthy plant growth. Research conducted over several years at The Ohio State University Soil Ecology Laboratory found that worm castings enhanced seed germination, plant growth, flowers and fruit production. Castings also curbed certain plant diseases, including root and crown rots and wilt disease, and inhibited some insect pests, including mites, aphids and mealy bugs.1

In 2011, researchers at Cornell University Department of Plant Pathology and Plant Microbe Biology demonstrated that worm castings suppressed damping-off disease in seedlings. In addition, castings naturally degraded the protective covering of some insect pests, regulated plant nutrient release and stimulated the nutrient cycle from soil to plants.2

How To Use Castings To Help Your Garden

Using earthworm castings is as simple as using traditional garden compost. Dry castings serve as soil-enhancing mulch, but their impact increases when they’re worked into soil before planting or potting. Compost piles benefit from castings, too.

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Worm Castings – What are they? How do they work?

Worm castings are the richest natural fertilizer known to humans. That’s right: as little as a tablespoon of pure worm castings provides enough organic plant nutrients to feed a 6″ potted plant for more than two months. Worm castings stimulate plant growth more than any other natural product on the market. Unlike animal manure and artificial fertilizers it is absorbed easily and immediately by plants. But Worm Castings don’t only stimulate plant growth: they also enhance the ability of your soil to retain water (because of its texture), and it even inhibits root diseases such as root rot.

You can order worm castings in our catalog.

What Are Worm Castings?

Worm Castings contain a highly active biological mixture of bacteria, enzymes, remnants of plant matter and animal manure, as well as earthworm cocoons (while damp). The castings are rich in water-soluble plant nutrients, and contain more than 50% more humus than what is normally found in topsoil.

Worm Castings are packed with minerals that are essential for plant growth, such as concentrated nitrates, phosphorus, magnesium, potassium and calcium. It also contains manganese, copper, zinc, cobalt, borax, iron, carbon and nitrogen. However, the best of all is that these minerals are immediately available to the plant, without the risk of ever burning the plant. Remember that animal manure and chemical fertilizers have to be broken down in the soil before the plant can absorb them.

As the organic matter moves through the alimentary canal of the earthworm, a thin layer of oil is deposited on the castings. This layer erodes over a period of 2 months. So although the plant nutrients are immediately available, they are slowly released to last longer. The cocoons in Worm Castings each contain between 2 and 10 eggs that hatch within 2 weeks. This means that the process of decomposition are continued by the young earthworms in the soil, provided that the soil is loose, damp and rich enough in organic matter for the worms to stay alive.

The bacteria in the alimentary canal of the earthworm transforms organic waste to natural fertilizer. The chemical changes that the organic wastes undergo include deodorizing and neutralizing. This means that the pH of the castings is 7 (neutral) and the castings are odorless (they smell like a forest after rain). The worm castings also contain the bacteria, so the process is continued in the soil, and microbiological activity is promoted.

What Can Worm Castings Be Used For?

Worm Castings can be used as an ingredient of potting soil (as plant nutrients) for plants in and around the house. It can also be used as a planting additive for trees, vegetables, shrubs and flowers. When used as mulching material, Worm Castings will ensure that the minerals are absorbed directly into the soil when it is watered. Because Worm Castings will never burn plants, you can use as much of it as you like.

Benefits of Worm Castings

  1. The humus in the worm castings extracts toxins and harmful fungi and bacteria from the soil. Worm Castings therefore have the ability to fight off plant diseases.
  2. The worm castings have the ability to fix heavy metals in organic waste. This prevents plants from absorbing more of these chemical compounds than they need. These compounds can then be released later when the plants need them.

  3. Worm Castings act as a barrier to help plants grow in soil where the pH levels are too high or too low. They prevent extreme pH levels from making it impossible for plants to absorb nutrients from the soil.

  4. The humic acid in Worm Castings stimulate plant growth, even in very low concentrations. The humic acid is in an ionically distributed state in which it can easily be absorbed by the plant, over and above any normal mineral nutrients. Humic acid also stimulates the development of micro flora populations in the soil.

  5. Worm Castings increase the ability of soil to retain water. The worm castings form aggregates, which are mineral clusters that combine in such a way that they can withstand water erosion and compaction, and also increase water retention.

  6. Worm Castings reduce the acid-forming carbon in the soil, and increase the nitrogen levels in a state that the plant can easily use. Organic plant wastes usually have a carbon-nitrogen ratio of more than 20 to 1. Because of this ratio, the nitrogen is unavailable to plants, and the soil around the organic waste becomes acidic.

Recommendations and Quotes about Worm Castings

“Worm Castings outperform any commercial fertilizer I know of. The key factor is microbial activity. Research that I and others have done shows that microbial activity in worm castings is 10 to 20 times higher than in the soil and the organic matter that the worm ingests…”

“Earthworm castings are the best imaginable potting soil for greenhouses or house plants, as well as gardening and farming. It will not burn even the most delicate plants and all nutrients are water-soluble, making it an immediate plant food. The effect of earthworm castings used in any of these ways is immediately visible. They make plants grow fast and strong.”

“Castings contain 5 times the available nitrogen, 7 times the available potash and 1 1/2 times more calcium than that found in 12″ of topsoil. Therefore, castings are supplied with available nutrients. The nutrients are also water-soluble and immediately available to the plant. You will find that most potting soils have a nutrient life for 2 to 5 days, where worm castings will last up to 6 times as long. You will need 5 times as much potting soil to do the same job as worm castings. So in the long run, worm castings are much cheaper and do a much better job. Also, castings hold 2 to 3 times their weight in water. That means you water less and the pot will stay damper for a longer period. Worm castings will not burn your plants; unlike using any fresh raw manure (cow, horse, etc.) which can burn root systems if not applied properly. . . . The manure passes through the worms’ digestive system producing rich organic plant food and a slow releasing fertilizer which allows for better growth.”

How to use Worm Castings:

For Germination

Use 20 to 30% Worm Castings with sand as an excellent germination mixture. It will also ensure continuous and lush growth for about three months, without you having to add any other plant food.

As a Soil Conditioner

If you hoe a layer of barren soil, add a layer of Worm Castings and give it some water, you will be surprised at the growth of your first season’s plants.

As a Fertilizer

Sprinkle Worm Castings around the base of plants or lightly dig it in, and then add water. They can also be sprinkled on a large scale with a spreader. Remember: you cannot use too much Worm Castings, they cannot damage your plants.

As a Liquid Fertilizer

Worm Castings can easily be mixed with water. Use 1 cup Worm Castings for every gallon of water and wait 1 week. This liquid mixture can be used as an excellent fertilizer or leaf foliate spray. It also helps to control insects. Many people prefer this method of application.

We have known for hundreds of years that earthworms are the best way to improve plant growth and to increase plant yield, such as fruit. Earthworm castings are a wonder product of nature. So if you care about your soil, and your plants, then now is the time to get rid of your Miracle Gro and to use this 100% natural product.

How Castings Are Grown and Harvested

Large wooden boxes are kept in a greenhouse with low light conditions and moist warm air. The boxes are filled with manure, cottonmeal, peat moss and other natural products and then worms are added.

As the worms eat their way through this material, they digest it and it breaks down and becomes worm castings. The worms are carefully separated out and the castings are bagged up for you. Many times worms leave tiny eggs in the castings which later hatch and become great worms for your garden to continue their work!

The ability to harvest small handfuls of worm castings as needed is a thing of composting beauty. However, in order to ensure that your vermicomposting system diverts the greatest volume of organic material and supports the healthiest worm population, it’s important to fully harvest and refresh the tray(s) every so often!

You will know that a harvest is on the horizon when bin contents have dropped substantially and the original bedding material is practically unrecognizable, having been replaced by brown, earthy vermicompost and castings. (For a distinction between the two yields, check out THIS POST)

When harvesting castings, the trick is to separate out and keep as many worms as possible. Any escapees won’t wreak havoc in your garden, but they are more likely to survive and thrive in the hospitable environment of the worm bin. Plus, red worms are ideally a one-time investment; a multi-generational family of worms will perpetually produce nutrient rich castings as long as they are kept in the bin!

There are a variety of ways to harvest worm castings. Here are a few of the most common methods:

Worms will follow food scraps, and given a little time, can actually be guided to sort themselves from their castings. The key is to STOP feeding the area you wish to harvest, and ONLY add food to the area with fresh bedding. The worms will travel to the new area in search of food, leaving you with (virtually) worm-free castings to harvest. After harvesting, replenish the now-vacant side or tray with new bedding and food scraps to restart the process. Isn’t it nice when the worms do all the work?

There are two general ways to implement the migration method:

(1) If your worm bin is comprised of a SINGLE TRAY, the worms will need to travel horizontally to one side of the bin. Move material to be harvested to one side of the bin, and replenish the other side with fresh bedding and food scraps.

(2) If you want to utilize MULTIPLE TRAYS, the worms will need to travel vertically (either up or down) to a newly-prepared tray with fresh bedding and food scraps.

PRO: This easy, self-contained process is mostly hands-off; useful for anyone who is queasy about handling the worms or getting a little messy.
CON: Expect waiting 1-4 weeks (depending on the size of the bin) for a good proportion of the worm population to relocate to their new home.

Worms are highly sensitive to light, and will readily move away from light sources. By strategically introducing light, worms can be guided to burrow to a desired location, allowing for easy collection of the remaining castings. If outdoors, choose a sunny location to work; if indoors, place the piles under bright light for the entire process.

There are two general ways to implement the photosensitivity method:

(1) The VOLCANO/CONE METHOD is practiced by emptying out the bin contents onto a stable surface (that you don’t mind getting dirty) and sorting the castings into loosely-packed, cone-shaped piles. The worms will continually burrow away from the edges to escape the light, allowing you to scrape the worm-free castings off of the tops and sides of the piles. Take a 15 minute break after each round of castings removal to allow worms time to move inward. Repeat this process several times until only small piles of worms and castings remain; these can be placed into a bin with fresh bedding and food scraps.

(2) The BURLAP/FILTER METHOD is practiced by first emptying out bin contents into a temporary holding area, and immediately replenishing the empty bin with fresh bedding and food. Place a piece of damp loosely-knit burlap (or any mesh cloth with openings large enough for worms) over the bin allowing it to hang over all edges. Spread a thin (approx 1 inch) layer of castings on the burlap. Wait for at least 20 minutes for the worms to burrow away from the light source, directly into their new home. Worm-free castings can then be removed from the top of the burlap. Repeat this process until all bin contents have been separated.

PRO: Fairly organized and immediately gratifying processes that allow the harvester to multi-task.
CON: Not for the easily distracted; worms that are left in the sun for too long will not survive the ordeal!

If you love getting to know your worms up close and personal, this slower-paced, hands-on style may just be the method for you.

There is essentially no planning or technique required with this method; simply dump out the bin contents (probably onto a surface you don’t mind getting dirty) and remove the worms from the castings by hand. Worms should soon after be placed into a bin or tray with fresh bedding and food scraps. While less organized than the other methods, this strategy is perfectly effective as long as you don’t mind spending a little extra time sorting through castings.

PRO: Immediately gratifying, lots of fun for those who enjoy handling the worms, and a great activity for kids!
CON: Not a recommended method for the impatient or for those looking for a time-efficient technique.

Happy Harvesting!

How to harvest worm castings.

When and how to harvest worm castings is one of the first questions aspiring worm farmers usually ask me when they

purchase a worm farm from me. This is not surprising because worm castings are surly one of the greatest benefits we can derive from worm composting. Being one of nature’s best organic fertilizers and soil conditioners many are keen to put worm castings into action in their gardens.

Many ways are leading to Rome and there are as well several ways you can harvest worm castings. Below I will show you the probably easiest way to harvest worm castings from a multiple tier worm farm.

No matter if you are working with a 3 tier or 5 tier worm farm, the process of separating the worm castings from the worms and the food is basically the same.

If you have a Single worm bin please follow the link at the bottom of this page to our worm castings page for harvesting instructions.

But lets get back to the “multiple tier worm bins”

A 3 tier worm bin starts off with the worms, bedding and food in the second or middle bin.

The top bin will be empty and the bottom bin will be the place where the excess liquid will be collected before it’s drained off.

3 tier worm farm with empty top bin!

Regularly add food to the middle bin of your worm farm right on top of the worm bedding.

The worms will feed on the organic materials you add to the worm bin, digest them and deposit them on top of their bedding as worm poop or worm castings.

A 3 tier worm farm with the top bin about half filled up.

Repeat this cycle till the middle bin will be full to the top. Then start adding food to the top bin.

Compost worms are top feeders and will always follow the food supply upwards. So with time more and more worms will migrate into the top bin. You can assist this migration by always adding a handful of bedding and worms from the middle bin to the top bin when you are adding food for the worms.



When your top bin is more than half full most of your compost worms should have left the middle bin.

How to harvest worm castings

Now it will be time to harvest the worm castings from your middle bin. At this stage there should be no food left in the middle bin. To remove the remaining worms from the bin add a thin layer of food to it about 3 days before you want to harvest the castings.

On the day you want to harvest, remove the remaining food plus the top 5 cm / 2 inches of worm castings beneath the food from the middle bin. This way you will move the remaining worms from the middle bin and add them to the top worm bin.

The worm farm after the harvest of worm castings.

Now you can harvest the pure worm castings from your middle bin. Drop the bin that is holding the food and worms to the middle of your 3 tier worm farm and place the

empty bin on top. Depending on the size of your worm bins and the amount of worms they hold you should be able to harvest fresh worm castings every 6 to 8 month this way!

Keep it up and Happy Worming!


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Harvesting worm castings

Worm castings are worm poo – there’s no simpler way of putting it. But it makes good fertalizer for plants. Harvesting worm castings means removing it from the bin for making use of.

There are many ways to harvest worm castings:
1. dump and sort
2. let the worms do the sorting
3. divide and dump
4. alternate containers
5. mechanical harvester
I talk about each of these methods near the bottom, though I’ve tried only the first two.

After two years of worm composting the layer of worm castings at the bottom of my bin was getting fairly deep. This meant that the layer of bedding at the top of the bin was getting thinner and allowing odors to get out easier. So I decided to harvest some worm castings.

The method I used was to dump and sort, described below.

Gently scoop out some material from the worm bin and dump it in a pile(s) on a piece of newspaper or plastic. The newspaper will probably soak through so only use newspaper if that’s okay. The material consists of much more than just the worm castings: castings, worms, leaves, bits of newspaper, worm cocoons, … Your job is to separate out just the castings from rest and put the rest back in the bin. Worm cocoons are basically worm eggs from which baby worms will hatch. They look like small 3mm (1/16″) diameter shiny beeds.

The worms will make this job easier for you because they hate light. Any worms on the top of your pile will immediately head deeper down into the pile, leaving the top worm free.

Have a shaded area for any worms that you do remove from the pile.

The worms quickly disappear deep into the pile to get away from the sun, making it easier to pick out the worm castings from the top. Any worms taken from the pile should be kept in the shade. Add some castings, leaves and such for them to escape under.

With the above method, I can fill the small half litre yogourt container in about 10 to 15 minutes. Since I use newspaper for my bedding, the last thing I did was to tear up the newspaper and add it to the bin.

Here’s a video of the whole process.

Worm castings harvesting methods

1. Dump and sort

This is the method described above.

2. Let the worms do the sorting

The worms go where the food is. So don’t put any food in one area of your bin for a month or two and any worms in that area will leave for areas that do have food. Voila. After the month or two is up, remove the worm castings.

I did try this once, but even after a few months, there were still plenty of worms in that selected area. But, many others have had success with this method.

3. Divide and dump

This is the simplest of all methods. Simply take material from one area of your bin, worm castings, worms, cocoon, et al, and dump it in your garden. Put fresh bedding in the area that you removed the material from.

4. Alternate containers

Have more than one worm bin. After one is full of food, leave it alone and start using another one. After all the food has been consumed, simply dump the contents of the bin in your garden, add new bedding and food along with some worms from another bin.

5. Mechanical harvester

The material from your bin should be fairly dry for this to work. This uses a drum or cylinder which sits on it’s side, angled slightly downward. You put the material to be harvested in the drum near the top and then rotate the drum. As you do so, the castings separate from everything else. Near the bottom edge of the drum is a mesh or grate which allows the worm castings to fall through into a container. Some other material may fall through too, such as small worms and worm cocoons. I’ve never tried this method myself.

In addition to the beneficial microbes, the USDA says that worm castings are “several times higher in nitrogen, phosphorus, potassium, and magnesium than topsoil.” The nutrients in all-natural worm castings are substantial and they provide the perfect mix that marijuana plants need.

The bottom line is that worm castings mixed in with your soil will pay big dividends when it comes to harvesting marijuana.

Protects Marijuana Plants Naturally

Worm castings have the ability to protect your marijuana plants from both diseases and pests without the use of harmful chemicals. This study from Cornell University found that earthworm castings can stop many common plant diseases.

According to the study, castings “can colonize a seed’s surface and protect it from infection by releasing a substance that interferes with the chemical signaling between the host and the pathogen.” These pathogens are a common issue for many greenhouse growers when attempting to grow marijuana and other plants indoors.

Worm castings help form a protective barrier at the microbial level, that will keep your plants growing even if they’re exposed to potentially harmful diseases.

In addition to protecting against disease, castings also help keep pests at bay. Microbes in worm castings naturally stimulate the production of chitinase, which breaks down the exoskeletons of many insects.

This provides a natural and safe form of pesticide without all the synthetic chemicals. You can save money on pesticide, while at the same time keeping your plants healthy for consumption.

A Little Goes a Long Way

When being cost-conscious, you don’t want to spend to much on fertilizer or soil supplement. If you’re in need of a cost-effective solution, worm castings are the way to go. While you really can’t use too much, you don’t have to overdo it either.

Many growers use a mix of 25% earthworm castings to 75% soil. That’s typically enough to make a big difference for the plants. In some cases, growers make an earthworm castings tea by soaking the castings in water and then spraying the plants with the mixture. This allows you to get even more bang for your buck and help your marijuana plants throughout the growth cycle.

Another nice thing about worm castings is that you really can’t screw it up. If you put too much in the soil, it’s not going to burn the plants. It’s totally safe to handle and it won’t have any negative affect on the plants if you accidentally put too much in.

In fact, you could grow marijuana plants directly in worm castings if you wanted to, although it’s probably not the most cost-effective route to do it on a large scale. If you try worm castings on your marijuana plants, you can tweak the mix to get just the right formula. The good news is that it’ll work well, regardless of what you do.

Choosing the Right Worm Castings Product

With as awesome as worm castings are, you might think that you’ll be fine no matter which one you buy. While worm castings are great in general, not all brands are created equally. What are some things that you should look for when buying the best fertilizer for marijuana?

  • Percentage of purity
  • High-quality food source for the worms
  • Controlled process that ensures quality castings
  • Guaranteed results
  • Trusted brand

Simple Grow Soil Builder is the highest-quality worm casting product on the market. We offer various size bags of worm castings to cover whatever size planting area you have. Needing more than 1 ton?

When you have a vermicomposting system, you periodically need to harvest your worm castings. This nutrient-rich “black gold” is the perfect fertilizer for your plants. Harvesting also helps keep the worms healthy. You will know it is time to harvest when most of your worm bedding has been turned into a rich, dark, soil-like substance of vermicompost and castings.

There are several good methods for harvesting worm castings for small home-based vermicomposting bins. Which method you choose will depend on the type of system you have set up, and on your personal taste.

There are single tray vermicomposting systems, stackable multi-tray systems and many do-it-yourself systems. Choose a method that efficiently extracts the casting while leaving enough worms behind to keep composting.

Method One: Encourage Worm Relocation

A very popular method for harvesting, the worm relocation method is based on the fact that worms will migrate towards food. In a single tray system, gather whatever uncomposted scraps remain in the castings and move them to one side of the tray, or to the center. Add fresh food only in the spot you want the worms. In a multi-tray vermicomposting system, put food in the tray above the one you want to harvest. In a matter of one to four weeks, depending on the size of the tray, most of the worms will naturally migrate to the food source. This will leave you with nearly worm-free castings to harvest. At this point, you can also fish out any remaining eggs, which are small and yellow, and will yield more worms in the future. This method is great for anyone who feels squeamish about touching worms.

Method Two: Relocation by Light

Worms will automatically move away from light, so applying artificial light or sunlight to your castings can also yield worm-free castings. Caution: Never expose your worms to excessive sunlight or heat, or they may dry up and die.

You can try one of two things:

  • Gently dump out your worm tray on to a clean, stable surface and build mounds of castings. In about twenty minutes, the worms will burrow down to the bottom and away from the sides to escape the light. You can then scrape off the tops and sides of the pile, working in, until only small piles remains. Or,
  • Gently put the worm castings into a temporary holding container. Add more food and bedding to the now-empty worm tray. Take a piece of burlap or other material with worm-sized holes and drape it over the worm tray. Spread a thin layer of castings and worms, 1-2 inches thick, over the cloth and wait twenty minutes. By then, the worms will have burrowed down into the worm tray. Put the worm-free castings into a storage container, and apply them to your plants’ soil.
    Note: Instead of burlap, you can construct your own filtering trays using wire mesh. This method must be done in a timely fashion so that the worms can stay damp. Both sunlight and human hands can dry out worms, which can harm them.

Method Three: Hand Harvest

For those who are willing to do things at a slower, more intimate pace or who, only need a few handfuls of castings right at the moment, this method may be desirable. Simplest of all, it only requires gathering up handfuls of castings and sifting through them for worms which can then be placed back in the tray. You can dump out the whole tray at once and reload it with food bedding and sort through it all. Or you can choose just a few handfuls if it is not an appropriate moment for a full harvest. Children often enjoy the fun of this kind of sorting.

Method Four: Screen Compost

Sift the worm bedding through a screen and you will separate the worms, sticks, and undigested material from the finished compost easily. Screened compost is especially valued because it’s light and fluffy, and free of debris. You can buy or make a composting screen. See our instructions for screening compost.

After your worm castings are harvested, they can be stored in a sack, clean bucket or other container until you are ready to use them. They are teaming with healthy soil bacteria and nutrients that are perfect for adding to soil. Help your plants and lawn grow strong, and keep your worm population happy by harvesting worm castings regularly.

Note: If you need more composting worms, just order worms online from Uncle Jim’s Worm Farm. We have been in the worm business for more than 25 years, so we must be doing something right! They are guaranteed to arrive alive or we will replace them.

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