Worm Castings Are the Secret to Healthier Soil and Stronger Plants – Here's How to Make Them at Home

Worm castings are one of nature’s little miracles, which is a bit surprising considering what they are. Worm castings are essentially the fecal matter from worms. These wriggly garden residents are wonderful at eating up organic refuse and turning it into a material full of useful nutrients for your plants.

You can purchase earthworm castings at most garden centers or get organic worm castings online from Amazon, but a more economical way to harness the benefits is to create your own vermicomposting setup. Red wigglers are the primary type of worm used to eat up kitchen scraps and create this magic soil amendment.

Adding worm castings to the soil aerates and improves its overall structure while providing beneficial nutrients to plants. They are also effective for repelling many pests that feed on plants. Keep reading to learn more about the benefits of worm castings, how to make your own, and how to use them in your garden.

Worm Composting Essentials

What Are Worm Castings?

Worm castings, which is basically just worm poop, is an amazing soil amendment for your garden. When worms eat organic matter, they excrete it in the form of little mounds of slightly muddy matter. Also known as vermicast or worm manure, castings are highly prized among organic gardeners. But worm castings aren’t just digested food. They are also made of enzymes and beneficial bacteria.

Good quality worm castings should be dark brown, slightly moist yet crumbly, and smell like soil. They contain as much as 50% more humus than what is normally found in topsoil. Worm castings resemble football-shaped particles that improve soil aeration and drainage, as well as increase water retention in the soil. They are water soluble, too, which means they are easy to quickly deliver nutrients to plant roots.

You can purchase worm castings at most garden centers nowadays or you can even find them online from Amazon, but they can be a bit pricey. Although, you don’t need a huge quantity to make a big difference in your garden.

What Do Worm Castings Look Like?

Worm castings are crumbly and look a bit like used coffee grounds. They should be nearly the same color, too. They are slightly moist and cling together. Earthworm castings have no smell beyond freshly turned earth.

If you go out to a spot in the dirt in your garden where worms are present, you will likely find little piles of worm castings especially after watering or a rain.

Benefits of Worm Castings

Worm castings are an excellent organic alternative to synthetic fertilizers for several reasons. Not only can you use this worm castings on nearly any type of plant, but you can also use them directly around plants without fear of fertilizer burn like conventional plant foods cause. Simply apply worm castings as a top dressing, side dressing, or work it into the soil.

They contain a high quantity of the important NPK macronutrients that plants need. The ratio of each varies depending upon what the worms have eaten, but overall they release loads of macro and micronutrients as well as trace minerals. Nitrogen, phosphorus, potassium, calcium, and magnesium are plentiful. Minerals and other elements like zinc, copper, sulfur, and iron are also present.

Worm castings enrich the soil and improve soil solubility, which allows plant roots to quickly take up nutrients. They enhance the soil by increasing percolation and aeration, too.

The beneficial microbes in worm castings can also help plants fight off diseases like damping off as well as crown rot and root rot. The reason for this is an enzyme called chitinase. Plants absorb this after you apply worm castings. Then when insects feed on the plant, the enzyme dissolves their insides and they die. This enzyme is effective against fruit flies, some hard-shelled bugs, spider mites, aphids, whiteflies, and other common garden pests.

Drawbacks of Worm Castings

One of the main disadvantages of worm castings is the amount of work required to make just a small amount of this soil amendment. With a typical home vermicomposting station, you can only produce enough castings to fertilize your houseplants or a small part of your garden.

You can buy premade worm castings that are ready to apply directly to your plants, but they can be a bit costly. Though they are rich in nutrients, so you don’t need enormous amounts to make a difference with your plants.

For a big vegetable garden, the best way to harness the benefits of castings is to encourage earthworms. A large earthworm population will enhance the soil naturally. To encourage earthworms, use no-till techniques, incorporate organic matter into your soil, and try to keep a slightly acidic to neutral soil pH.

You can also invest in an in-ground worm composter, like this one from Vego Garden, to bring more worms to your garden. Simply bury the in-ground worm bin in your garden, then place kitchen scraps and organic waste into it, and wait for the worms to arrive.

How to Make Worm Castings

Making worm castings at home is easy, but potentially a bit messy. You can buy premade worm bins from Amazon or you can make your own. To make a worm bin, you need just a few items: kitchen scraps, red wigglers, which you can also order online from Amazon or get at some plant nurseries, and a couple of plastic totes.

You will need two totes that can nest into each other. They should be no more than 1 foot (30 cm) deep. If they are too deep, they may become problematic with odors. Also, smaller bins work better in the home because they can fit beneath the sink or in another corner of the kitchen. You will also want a lid for your bin because the worms for vermicomposting are sensitive to light.

Drill holes in the bottom of one of the bins and some holes around the sides for air. The bottom holes will drain any fluids. Place something in the bottom bin to keep the upper bin up and away so drainage can occur. This could be some stones or a couple bricks, anything you have lying around.

If you wish, you can install a drain on the bottom tote to release the liquid into another vessel. This will prevent any unsavory smells from your worm bin. Plus, this liquid, called worm casting tea, is a great fertilizer for your garden.

Add wet, shredded newspaper to cover the bottom of the upper tote, then top it with a couple inches (5 cm) of compost or another layer of moist newspaper strips and soil, and add your red wigglers. Finally, add kitchen scraps or garden waste, then top the whole thing with a lid that has had ventilation holes drilled into it.

You need to regularly feed your worms with kitchen scraps to get them to produce lots of castings. Follow the same rules as composting and avoid meat, bones, dairy, and oils. Keep the compost in the bin slightly moist.

How to Harvest Worm Castings

After about four months, it should be time to start harvesting worm castings. There are a couple different methods for doing so.

One of the most popular is the dump and sort method. Simply lay out a sheet of plastic or newspaper and empty out the contents of the worm bin. Collect the worms and add them to a fresh vermicompost bin, then use the leftover castings on your plants.

Another popular method is to stop feeding your worms for a week, then push the contents of your worm bin to one side and add fresh bedding and food to the other side. In a couple more weeks, the wigglers will migrate to the side with the food and bedding materials.

Then you can safely scoop out the vermicompost, without harming your red wigglers. The lower bin will also contain the moisture that has come through the compost. Pour this worm casting tea on your garden soil around plants to give them an extra boost.

How to Use & Store Worm Castings

Keep worm castings in a plastic bag or a lidded bin in a dark location until you are ready to use them. They may need occasional misting to keep them moist. You will also need to open the bag or bin every week to let out any excess moisture, so they don’t mold.

To use worm castings, add them to potting soil, mix them into your garden soil, turn them into fertilizer tea, or use them to make a foliar spray. To make worm casting tea, soak the castings in water for a few days, then strain. For a spray, take this liquid and dilute it in a ratio of 1:20 with water. Spray on the leaves of garden plants or houseplants.