Garden tea, specifically known as actively aerated compost tea, is a liquid soil amendment that organic gardeners use to enhance plant health and promote nutrient uptake. It is essentially a microbe-rich water extract made by brewing high-quality compost. This process creates a living liquid that can be applied directly to the soil or sprayed onto plant foliage to boost the garden ecosystem. The popularity of this method stems from its ability to introduce beneficial microorganisms into the soil environment without relying on synthetic fertilizers or chemical treatments.
The Biological Purpose of Garden Tea
Brewing garden tea extracts and multiplies beneficial microorganisms, such as bacteria, fungi, protozoa, and nematodes, present in mature compost or worm castings. The process transfers these diverse microbial communities and soluble nutrients from the solid compost material into the water. This liquid inoculates the soil and leaf surfaces with a high concentration of beneficial life.
When applied, the tea introduces these microbes to the rhizosphere, the area directly around the plant roots, where they play a significant role in nutrient cycling. These organisms help convert compounds into forms that plants can readily absorb, improving overall plant nutrition. Coating the leaves with this microbial community via a foliar spray also suppresses pathogens by outcompeting disease-causing organisms. This biological action improves soil structure, increases water retention, and enhances the plant’s natural resistance to pests and diseases.
Essential Materials and Ingredients
The brewing process requires specific materials to ensure the resulting tea is rich in beneficial aerobic microbes. The foundation of the tea is the microbial source, which must be high-quality, fully aged compost or vermicompost (worm castings). Using mature compost minimizes the risk of multiplying harmful pathogens during brewing.
The liquid base must be non-chlorinated water, since chlorine in tap water destroys the beneficial microorganisms. Tap water can be prepared by letting it sit out in an open container for 24 hours to allow chlorine to dissipate, or by treating it with a dechlorinating agent. An aquarium air pump and an air stone or bubbler are needed to ensure active aeration. The air pump maintains high dissolved oxygen levels, which encourages the growth of beneficial aerobic microbes and prevents anaerobic organisms.
A microbial food source is added to stimulate the rapid reproduction of beneficial organisms during aeration. Common sources include unsulphured molasses, which feeds bacteria due to its simple sugar content, and liquid kelp or fish hydrolysate, which encourage fungal growth. Equipment includes a clean, five-gallon bucket and a fine-mesh bag, such as a nylon stocking, to hold the compost material. This bag prevents large debris from clogging the air pump or sprayer nozzles during application.
Step-by-Step Brewing Instructions
The brewing process begins by preparing five gallons of non-chlorinated water in the bucket, ensuring that tap water has been left to sit overnight or treated to remove chlorine. The air stone is placed at the bottom, and the air pump is turned on to begin aeration. Maintaining constant aeration is essential, as it keeps the environment oxygen-rich for the beneficial microbes.
Next, one to two cups of mature compost or worm castings are placed into the mesh bag and secured. This “tea bag” is submerged into the actively aerating water, allowing the flow to extract the microorganisms. Following this, the microbial food source is added directly to the water, typically one to two tablespoons of molasses or liquid kelp for a five-gallon batch.
The mixture is left to bubble continuously, with the optimal brewing time generally falling between 24 and 48 hours. The duration depends on the ambient temperature; warmer conditions, ideally between 68°F and 72°F, allow the tea to finish brewing sooner. A batch is finished when the water turns a light, earthy brown color and possesses a fresh, earthy aroma, similar to that of good soil. The absence of a foul smell confirms the tea has remained aerobic and is safe to use.
Proper Application and Storage
Once the garden tea has finished brewing, the first step is to remove the air stone and the mesh bag containing the spent compost. The liquid should be used immediately after the aeration process is stopped to ensure the beneficial microbes are still active and abundant. The tea is highly perishable because the microbial population will quickly die off without the continuous supply of oxygen provided by the air pump.
The finished product can be applied as a soil drench, poured around the base of plants to inoculate the root zone and improve soil health. Alternatively, it can be used as a foliar spray to coat the leaves, helping microbes outcompete disease organisms on the plant surface. If using a sprayer, the tea should be strained again to prevent small particles from clogging the nozzle. The tea is often used undiluted or diluted with non-chlorinated water at a 1:1 ratio.
The best time for application is in the early morning or late evening, as cooler temperatures and lower ultraviolet light levels are more conducive to microbial survival. Applying the tea during the heat of the day or in direct sunlight can kill the microorganisms on the leaves. The tea should be completely used within four to six hours of turning off the aerator to maximize the benefit from the living microbial solution.