A wormery, also known as a vermicomposter, is a contained system that uses specific worm species to convert organic waste into a highly beneficial soil amendment called vermicast or worm castings. This process, known as vermicomposting, efficiently manages kitchen scraps and produces a nutrient-rich fertilizer. The resulting castings and the liquid runoff, sometimes called leachate, are valuable products that enhance soil health and fertility.
Planning Your Wormery and Gathering Materials
The foundation of a successful wormery begins with selecting the right container system. Simple, opaque plastic storage bins or five-gallon buckets are effective, as worms prefer dark environments and plastic retains moisture well. A stacked system, often made of two or three nested containers, is popular because it allows worms to migrate upward toward new food, simplifying later harvesting.
Before construction, gather materials for the bedding, which serves as the worms’ home and a secondary food source. Ideal bedding materials are carbon-rich, such as shredded newspaper (black ink only), corrugated cardboard, coco coir, or peat moss. You will also need a drainage spigot or a collection tray for the bottom container to manage the liquid runoff. A small amount of grit, like crushed eggshells or soil, is needed to help the worms digest their food.
Constructing the Container System
The physical modification of your containers must prioritize both drainage and aeration. If using a stacked system, the base container, or sump, should remain undrilled to collect liquid (leachate). This sump can be fitted with a tap or spigot near the bottom for easy drainage of the liquid fertilizer.
The working trays placed above the sump require numerous drainage holes drilled across their base. These holes, typically about one-quarter inch in diameter, allow excess moisture to escape and enable worms to move between levels. For ventilation, drill smaller holes around the top perimeter and in the lid of the uppermost container. This ensures adequate oxygen flow since worms breathe through their skin. The lid should fit securely to maintain a dark environment and exclude pests.
Introducing the Worms and Starting the Process
The most suitable worms for vermicomposting are epigeic species, meaning they are surface-dwellers that thrive in decaying organic matter. The preferred species is the Red Wiggler (Eisenia fetida or Eisenia andrei), known for its voracious appetite and rapid reproduction in confined spaces. These worms can typically be sourced from specialized worm growers or bait shops.
To prepare the bedding, mix and moisten the carbon materials until they feel like a wrung-out sponge. This damp environment is critical for the worms to breathe. Fill the working container about halfway with the prepared bedding, then gently introduce the worms and a handful of grit. For the first week, offer a small initial feeding, such as a cup or two of vegetable scraps, burying it just beneath the surface.
Long-Term Maintenance and Harvesting
Routine feeding should begin only after the worms have settled and started consuming the initial scraps, which may take up to a week or two. Composting worms can eat roughly half their body weight in food scraps daily once the colony is established. Avoid overfeeding, which can lead to anaerobic conditions and foul odors.
Acceptable Foods
Focus on:
- Fruit and vegetable peelings
- Coffee grounds
- Crushed eggshells
Foods to Avoid
Strictly avoid:
- Meat
- Dairy
- Oil
- Overly acidic foods like citrus
Maintaining the correct moisture level, similar to a damp sponge, is paramount. If the bin becomes too wet, add dry shredded cardboard or paper to absorb excess liquid. The ideal temperature range for Red Wigglers is between 55°F and 77°F. Keep the wormery in a shaded area outdoors or indoors to protect them from extreme heat or freezing. If fruit flies appear, burying food deeper and covering the surface with a worm blanket or a layer of fresh, dry carbon material can help suppress them.
Harvesting the finished vermicast typically occurs every three to six months, depending on the system size and worm population. In a stacked system, when the working tray is full, a new tray with fresh bedding and food is placed on top. This encourages the worms to migrate upward toward the new food source, leaving the finished castings behind. Alternatively, the “light method” involves dumping the finished compost into small cones on a tarp in a bright area. This allows the light-sensitive worms to burrow down, and then the top layer of finished castings can be scraped away.