By Cosmos Burnigham

Compost tea is a beneficial soil and plant tonic that is used to increase the availability of plant nutrients and propagate beneficial microorganisms for your garden’s rhizosphere. When compost is “brewed,” nutrients and microorganisms are extracted into highly aerated water, where the microorganisms grow and multiply rapidly. Thorough research and planning is crucial to the success of your compost tea. Most growers don’t do the proper research––yielding mixed results––so they dismiss the idea. This is usually the result of too many inputs creating a toxic environment for the microbes. If you’re a careful and patient grower, you can create a superior compost tea that boosts yields and enhances your terpene production while protecting your plants from disease, pathogens, and pests!

It’s important to understand that compost tea is not a fertilizer replacement; it’s a boost for your soil rhizosphere, helping to maximize your soil capacity and bring out the genetic potential of your plants. Compost teas can also be used as a foliar spray. Using the correct brew as a foliar spray provides nutrition and helps protect against pests and diseases above ground.

When brewing compost tea, the goal is to extract the beneficial microorganisms from compost and/or castings and multiply them, maximizing the amount present in the solution. When you introduce this dynamic community of organisms into your garden they instantly go to work, taking over and out-competing potentially bad organisms. In your soil they aid in water retention, nutrient cycling, healthy root growth, and disease prevention.

Clean water, oxygen, and a microbial food source create an optimal environment where aerobic microbes can grow and multiply rapidly. High-quality compost and castings should provide all the beneficial bacteria, fungi, and protozoa needed to make a premium compost tea. Since the microbes in a healthy soil system are primarily aerobic, the microbes you select should be as well. You should always use aerobic, fully aged compost from a trusted source. This helps ensure that your compost is disease free and won’t harm your plants.

Making compost tea can be done multiple ways, from oversimplified to highly complex and technical. The recipes in this article call for a simple yet highly effective tried-and-true method. All that’s required is a brew vessel (5-gallon bucket) with an air pump and air stone. Once you have your brew vessel set up, all you need to do is acquire your ingredients.


Oxygen is very important when brewing compost tea. If you don’t have adequate dissolved oxygen in your brew you will create an environment where anaerobic microorganisms can thrive and multiply, out-competing aerobic microbes and defeating the purpose of compost tea.


Compost and worm castings contain the correct microbial populations of bacteria and fungi that will help create a dynamic living soil. The organisms present in the compost and castings will be the microbes you are multiplying in your brew. The microbial food source you choose determines which microbe bacteria or fungi dominates your brew.


To simplify, there are two types of food sources: simple and complex. Bacteria favor simple food sources while fungi favor more complex food sources. Protozoa consume both bacteria and fungi, converting a small percentage into food for themselves and excreting the rest as plant-available nutrients.


If used correctly, bottled nutrients can simplify the brewing process. Most organic bottled nutrients contain some (if not all) your needed inputs. One good example available coast to coast is Roots Organics Surge, which contains hydrolyzed fish, kelp, and molasses. Surge alone doesn’t contain enough molasses for compost tea so one could add Roots Organics Trinity to the mix, which contains all the molasses needed along with kelp and some additional microbial food sources like yucca, humic acid, and aloe extract. If you’re looking to save time, try premixed concentrates like the ones listed above. If you prefer the basics or don’t have access to bottled nutrients, it’s important to know that you can brew a high-quality compost tea with just the basic microbial food sources listed below. For new brewers, starting with the basic ingredients can help give you a better understanding of how each food source works and what it provides.


Blackstrap Molasses – A complex sugar/carbohydrate source. Feeds mostly bacteria and some fungi.

Fish Hydrolysate – A complex food source. Feeds mostly fungi and some bacteria. Always use hydrolysate, which is enzymatically processed, leaving all nutrients, oils, and amino acids.

Kelp – A complex food source. Feeds bacteria and fungi. Provides a place for fungi to attach and float around while growing. Also, providing 60+ micronutrients, plant hormones, and growth regulators.


The length of time you brew your tea and the temperature you brew it at are both important factors when trying to select what grows in your brew. 24 hours is perfect if brewed at 70° F. If you wait too long, the number of bacteria and fungi in the solution lowers. This is due to a lack of food needed for bacteria and fungi to continue and multiply. Since protozoa continue to consume bacteria and fungi while they are unable to multiply, it quickly changes the population ratios.


The most important ingredient in your brew is the water so always know your water source! Dechlorinate when possible.


The temperature of your brew is important when trying to maintain a diverse community of microorganisms. The optimum temperature for brewing compost tea is 70°F. If it is below 65°F, organisms will grow and multiply at a slower rate. If temperatures get too high, specific microbial populations will begin to grow at a pace where they out-compete other microbes, lowering the genetic diversity.


Keeping your brew vessel and equipment clean should be a high priority. Being in charge of selecting the microbes you extract and multiply requires starting with a fresh batch each time. If you let dirt build up, use contaminated equipment, or brew with questionable ingredients you will never know what you’re brewing and introducing to your plants. Try using a “tea bag” to contain ingredients, which will help keep your brewing equipment clean. A “tea bag” can be pantyhose, a sock, a pillowcase, etc. There are even products made specifically for this application. Always clean your tea bag between uses.


Use this program alone and achieve great results or combine it with your current feeding program and maximize your return by building and maintaining a dynamic living soil system. Every batch starts with the Base Recipe. Depending on which stage your plants are at––clone, seedling, heavy veg., transition, or heavy bloom––flush the concentration dilution rate and supplements change by stage.

Designed to produce a microbial-rich tea. When used alone it acts as an inoculant, transplant aid, stress reducer, soil rejuvenator, soil conditioner, and foliar spray!