Worm castings are the best soil amendment that exists. That is not marketing — it is what happens when thousands of Red Wiggler worms process your kitchen scraps through their digestive systems, inoculating the material with beneficial bacteria, fungi, and enzymes along the way. The resulting castings contain plant-available nitrogen, phosphorus, potassium, calcium, and magnesium in a slow-release form that will not burn roots. They improve soil structure, water retention, and disease resistance all at once.
And you can produce them in your kitchen, garage, or basement with a bin that costs less than twenty dollars to build and takes up about 2 square feet of floor space. Vermicomposting is the easiest, most space-efficient way to turn food waste into garden gold — and once you start using castings in your raised beds, you will wonder why you ever bought synthetic fertilizer. Our DIY project guides cover everything from building raised beds to crafting garden trellises, and this worm bin is one of the simplest and most rewarding builds on the list.
What You Need
Two opaque plastic storage containers (8 to 10 gallon size): The kind you can buy at any hardware or home goods store. Dark-coloured is better — worms are sensitive to light and work more actively in the dark. The containers need to be the same size so they nest inside each other with a gap at the bottom.
A drill with a 1/4-inch and 1/16-inch bit: For drainage and ventilation holes. If you do not own a drill, a hammer and nail works for the smaller holes, though it is slower.
Shredded newspaper or cardboard: This is the worm bedding. Black-and-white newsprint or plain brown cardboard, torn into strips about 1 inch wide. Avoid glossy paper, coloured inserts, and cardboard with heavy printing or tape.
One pound of Red Wiggler worms (Eisenia fetida): This is roughly 1,000 worms. Order them online from a reputable worm farm or check with local composting groups — many vermicomposters are happy to share surplus worms. Do not use earthworms (nightcrawlers) from your garden — they are a different species that burrows deep into soil and will not thrive in a shallow bin environment.
Building the Bin Step by Step
Step 1: Prepare the Upper Container
This is the container the worms will live in. Drill 20 to 30 holes in the bottom using the 1/4-inch bit, spaced roughly evenly across the entire bottom surface. These holes allow excess moisture to drain into the lower container, preventing the bedding from becoming waterlogged. Waterlogged bedding goes anaerobic, starts to smell, and can drown your worms.
Next, drill two rows of small ventilation holes (1/16-inch bit) along the upper sides of the container, about 1 to 2 inches below the rim. Space them every 2 inches. These provide airflow — the worms and the microbes working alongside them are aerobic organisms that need oxygen. Do not skip the ventilation holes, even though you want the bin to stay dark and moist inside. Air exchange is essential.
Step 2: Prepare the Lower Container
The lower container catches drainage (called leachate) from the upper bin. Do not drill any holes in this container. It stays solid. Set it on a flat surface and place a few small blocks or jar lids in the bottom to create a gap of about 1 to 2 inches. Then nest the upper (drilled) container inside the lower one, resting on the spacers. The gap ensures the upper bin is not sitting in its own drainage.
Step 3: Prepare the Bedding
Fill the upper container about two-thirds full with shredded newspaper or cardboard strips. Moisten the bedding thoroughly — you want it damp like a wrung-out sponge, not dripping wet. The easiest method is to put the dry bedding in a bucket, add water, mix with your hands, then squeeze out the excess before transferring it to the bin. The bedding should glisten with moisture but no water should drip when you squeeze a handful.
Add a few handfuls of plain garden soil or finished compost to the bedding. This introduces grit (worms need grit for their gizzards, the same way chickens do) and beneficial microorganisms that help break down food scraps alongside the worms.
Step 4: Add the Worms
Place your pound of Red Wigglers on top of the bedding and leave the lid off in a lit room. The worms will burrow into the bedding within 15 to 20 minutes to escape the light. Once they have disappeared below the surface, place the lid on loosely — you want it to block light but not create an airtight seal. Some vermicomposters drill a few small holes in the lid as well, which is fine.
Give the worms 3 to 5 days to settle into their new home before feeding. They have just been shipped and handled, and they need time to acclimate to the new bedding and environment. Resist the urge to dig around and check on them — they are fine.
Feeding Your Worms
Red Wigglers eat decomposing organic matter — they are not actually eating your food scraps directly but rather the bacteria and fungi that colonize the scraps as they break down. This is why food takes a few days to show signs of worm activity; the microbes have to start the process first.
Feed these: Fruit scraps (banana peels, apple cores, melon rinds, berry stems), vegetable trimmings (carrot tops, onion skins, lettuce, potato peels), coffee grounds and paper filters, tea bags (remove staples), crushed eggshells, bread and pasta in small amounts, and plain cooked rice or grains.
Avoid these: Citrus in large quantities (the acidity bothers worms — a few lemon peels are fine, but not a bag of orange rinds), meat and fish, dairy products, oily or greasy food, spicy peppers (capsaicin irritates worms), and pet waste.
Start slowly — about half a pound of food scraps per week for your first month. Bury the scraps under the bedding in a different spot each feeding, working your way around the bin. This keeps the surface tidy, reduces fruit fly attraction, and gives each feeding spot time to be processed before you return to it. A healthy, established bin with one pound of worms can process roughly 3 to 4 pounds of scraps per week. Let the worms set the pace — if food is accumulating faster than they can eat it, feed less.
Moisture Management
The bedding should always be moist but never soggy. Check it weekly by squeezing a handful — one or two drops of water should come out, but not a stream. If the bedding is drying out (common in warm, dry environments), mist it with a spray bottle or lay a damp sheet of newspaper on top as a moisture blanket. If the bedding is too wet (common when feeding watery scraps like melon or cucumber), add dry shredded newspaper or cardboard to absorb the excess and leave the lid slightly ajar for a day to increase evaporation.
Check the lower container every week or two. If leachate has accumulated, drain it. Some people use this liquid in the garden, though its quality is variable — unlike worm casting tea (made by steeping finished castings in water), raw leachate may contain anaerobic bacteria and unfinished decomposition products. If you use it, dilute it heavily (10:1 water to leachate) and apply it to ornamental plants rather than food crops.
Harvesting Worm Castings
After 3 to 6 months, a significant portion of the bedding will have been converted to dark, crumbly castings. You will know it is time to harvest when the bin contents are mostly dark brown to black, with an earthy smell and very little recognisable bedding remaining. There are several methods for separating the worms from the castings.
Light separation: Dump the bin contents onto a tarp or plastic sheet in bright light (outdoors on a sunny day is ideal). The worms immediately burrow away from the light. Wait 10 minutes, then scrape off the top layer of castings — the worms will be concentrated in the bottom of the pile. Repeat, waiting and scraping, until you have mostly worms left. Return the worms to the bin with fresh bedding.
Side-to-side migration: Push all the bin contents to one side. Fill the empty side with fresh, moist bedding and start burying food only on the new side. Over 2 to 3 weeks, the worms migrate to the fresh food and bedding. Harvest the castings from the old side, worm-free.
Using Castings in Your Raised Beds
Worm castings are too valuable to spread like bulk compost. Use them strategically where they make the biggest impact. Mix a quarter-cup of castings into each transplant hole when setting out tomatoes, peppers, or other seedlings. Side-dress established plants with a thin ring of castings around the base, then water in. Top-dress seed rows with a light sprinkling of castings for improved germination and early growth.
For worm casting tea, add one cup of castings to a gallon of non-chlorinated water, stir well, and let it steep for 24 hours (aeration with an aquarium pump is even better). Strain and use as a soil drench or foliar spray. The tea delivers a concentrated dose of beneficial microbes directly to the root zone or leaf surface.
To understand how castings fit into a broader soil amendment strategy, our raised bed soil mix guide covers the complete recipe, and our article on sustainable gardening principles explains why building soil biology matters more than adding synthetic nutrients.
Pair Your Worm Bin with the Right Beds
Our sustainably crafted cedar raised beds are the perfect home for your worm castings. Deep beds, quality soil, and worm-powered amendments — that is the recipe for an outstanding garden.
Frequently Asked Questions
Will a worm bin smell bad?
A properly managed worm bin has no noticeable odour — it smells like damp earth at most. If your bin smells bad, you are either overfeeding (food is rotting faster than worms can process it), the bedding is too wet (anaerobic conditions), or you have added something you should not have (meat, dairy, or excessive citrus). Reduce feeding, add dry bedding, and ensure drainage holes are not clogged. The smell resolves within a few days once conditions improve.
What happens if I go on vacation?
Worms are low-maintenance. If you are gone for 2 to 3 weeks, give them a larger-than-usual feeding before you leave, add some fresh bedding, and make sure the moisture level is good. They will be fine. For longer trips (a month or more), ask someone to add a handful of scraps once a week and check the moisture. Worms can survive extended periods with very little food by eating the bedding itself — they will be hungry and fewer in number when you return, but they will be alive.
How many worms do I need?
Start with one pound (roughly 1,000 worms). Red Wigglers self-regulate their population to match available food and space. In a well-fed bin, they will double in population within 3 to 4 months. If you underfeed, the population decreases. You do not need to manage their numbers — they handle that themselves. Starting with one pound in an 8- to 10-gallon bin gives you a solid baseline that grows into a productive colony within a few months.
Can I use worms from my garden instead of buying Red Wigglers?
No. The worms you find in garden soil are typically common earthworms (Lumbricus terrestris or similar species) that live in deep burrows and feed on organic matter within the soil profile. They need depth, cool temperatures, and room to tunnel — none of which a shallow plastic bin provides. Red Wigglers (Eisenia fetida) are surface-dwelling composting worms that thrive in dense organic material, tolerate close quarters, reproduce quickly, and process food scraps efficiently. They are a different animal for a different job. Buy the right species and you will have much better results.