Compost is a valuable resource for every grower. It’s a slow-release source of nutrients, and it helps build soil fertility and manage moisture. Better yet, compost is like those probiotic yogurts you’ve seen advertised—it prevents plant diseases and keeps plants healthy by maintaining an active population of beneficial microbes around roots. You can get many of the benefits of compost even if your indoor garden is hydroponic or otherwise soil-free by brewing up some tea. Compost tea, that is.
What Is It?
Compost tea is simply water in which compost has steeped. The tea-brewing process releases the nutrients in compost and makes them available for plants to absorb right away. It can also increase the numbers of beneficial bacteria and fungi in the compost and stimulate their activity, which helps your plants fend off disease organisms.
How Do You Make It?
Scoop a few shovelfuls of well-rotted compost (fine-textured, dark brown, earthy smelling) into a large bucket or barrel.
Add water at about twice the volume of the compost.
Stir well immediately and then twice a day for three days.
Optional: Microbe populations grow even faster if you use an air stone (like those used in small aquariums) to introduce a steady supply of oxygen into the tea. Adding a few tablespoons of sugar, such as sulfur-free molasses, also revs up microbe reproduction.
Strain the liquid using a cheesecloth or burlap. Toss the remaining solids back into the compost pile.
How Do You Use It?
The color of your tea should be pale yellow or brown. If the tea smells foul, don’t use it—that means unsavory microbes have formed and the tea could actually harm your plants. It should smell sweet and earthy. If the tea is dark or opaque, dilute it with water, up to a 10:1 ratio. You can pour fresh compost tea directly on the roots of plants growing in soil with no further filtering. To use it as a foliar spray in any hydroponic system, filter the tea again through a finer mesh fabric, such as an old pillowcase, then pour it into a spray bottle. However you apply it, put your compost tea to work within a day or two of brewing it—the microbes soon begin to die off. Compost tea is a healthy supplement to your plants’ regular feeding regime, but remember it is no substitute for high-quality nutrients specifically formulated for indoor gardens.