Oyster mushrooms (Pleurotus species) are favored for home cultivation due to their rapid growth and adaptability, often utilizing low-cost agricultural byproducts. The bucket method simplifies the process, offering a high-yield, space-efficient solution by containing the substrate and providing controlled points for the mushrooms to emerge. This technique focuses on allowing the vegetative stage, called mycelium, to fully colonize the growing medium before triggering the fruiting phase.
Supplies and Substrate Preparation
A successful cultivation requires a clean, food-grade five-gallon plastic bucket with a lid and oyster mushroom grain spawn. The bucket needs a series of half-inch holes drilled evenly around the sides, staggered four to six inches apart, to serve as exit points for the mushrooms. A few small drainage holes should also be drilled into the bottom. The growing medium, or substrate, is typically a cellulose-rich material like chopped straw, hardwood sawdust, or wood pellets.
Before use, the substrate must be pasteurized or sterilized to eliminate competing molds and bacteria. Pasteurization involves soaking the substrate in water heated to 160°F to 170°F (70°C to 75°C) for at least one hour. Alternatively, cold-water pasteurization uses hydrated lime to raise the water’s pH to around 12.5, killing contaminants without heat. The substrate must be drained and cooled to room temperature before mixing with the spawn, achieving a moisture content that allows a slight drip when squeezed.
Inoculation and Bucket Setup
Inoculation combines the prepared substrate with the mushroom spawn, which is grain fully colonized by the mycelium. The recommended spawn rate is five to ten percent of the total wet weight of the substrate to ensure quick colonization. Using a higher percentage accelerates the process and reduces the risk of contamination.
Once the substrate has cooled, inoculation is performed by layering the substrate and spawn inside the bucket until it is full. The material should be packed firmly, but not excessively compressed, as the mycelium requires air pockets to grow. The lid is then secured, and the pre-drilled holes may be covered with breathable micropore tape to maintain moisture and prevent early contamination.
Colonization: The Incubation Phase
After the bucket is sealed, it enters the colonization phase, where the mycelium grows through the substrate. This process requires a dark environment and a stable temperature, ideally between 70°F and 75°F (21°C and 24°C), which encourages the rapid expansion of the mycelial network. This period typically lasts between two and four weeks, during which the bucket should remain closed and undisturbed. Successful colonization is confirmed when a dense, white, fuzzy growth is visible throughout the substrate and begins to emerge from the drilled holes.
Fruiting, Harvesting, and Subsequent Yields
The transition to the fruiting phase requires an environmental shift, demanding fresh air exchange (FAE), high humidity, and indirect light. The mycelium reacts by forming tiny knots of tissue, known as “pins,” which are the initial stages of the mushroom. To achieve these conditions, move the bucket to indirect sunlight and remove the micropore tape from the holes. Humidity must be increased to 85–95% relative humidity, often accomplished by misting the holes several times daily. Constant fresh air is necessary, as excessive carbon dioxide can cause long, thin stems.
Within a week of these changes, the pins will rapidly grow into mature clusters. Oyster mushrooms are ready for harvest when the caps flatten out, but before they curl upward and release spores. Harvest the entire cluster by gently twisting and pulling the whole group off the substrate surface. After the first harvest, the mycelium needs a brief resting period to recover and rehydrate before producing another crop, known as a “flush.” By maintaining humidity and FAE, the bucket can yield multiple subsequent flushes over several weeks.