How to Brew Compost Tea for Better Plant Health

When other gardeners ask how I amend my soil, the answer is almost always with compost tea.

Compost tea is a safe and natural fertilizer that revives and replenishes the soil food web, a highly complex ecosystem comprising a community of good and bad bacteria, fungi, protozoa, nematodes, earthworms, and arthropods.

To put it simply, the soil food web forms the foundation of your plants, and subsequently your food.

Above ground, compost tea envelops your plants in a protective “web” (or biofilm) of living microorganisms that helps reduce foliar diseases and increase the intake of nutrients.

For several seasons, I was brewing my own tea using the compost from my garden (like the castings from my worm bin or the black gold from my compost heap) and any number of add-ins: kelp meal, fish emulsion, fish hydrolysate, blackstrap molasses. A single brewing session almost looked like a science experiment!

And if you turn to the many sources online touting the “right” way to make compost tea, you would find more opinions and suggestions than you could ever try in a growing season.

In all honesty, brewing a batch of compost tea isn’t that tricky. I found that as long as I followed a few basic principles, like proper aeration and dilution, it was hard to mess up… but there could always be a better way.

Types of Compost Tea

Compost tea is a relatively nascent science, and there are endless variables when you take into account the quality of your compost, the makeup of your soil, and the plants growing in your garden.

A compost tea brewed from vermicompost, for example, might be bacterially dominant if you feed your worms more nitrogen (vegetable scraps) than carbon (shredded paper). Bacterial-dominated teas are ideal for vegetables, herbs, grasses, and annuals, which prefer more bacterial soil.

On the other hand, trees, shrubs, and perennials prefer more fungal soil, which is what’s typically found in a forest. The natural mulch formed by decomposing leaves creates a fungal environment for broadleaf and coniferous trees.

At home, fungal-dominated compost tea can be brewed from leaf mold or compost based heavily on brown materials, such as straw, sawdust, or wood chips.

Berries fall right in the middle, preferring a balanced compost tea that’s equally bacterial and fungal. The exceptions are blueberries, grapes, and other acid-loving plants, which thrive in fungal-dominated soil.

Type of Plant	Type of Compost Tea
Brassicas	Highly bacterial
Herbs, vegetables, other annuals	Moderately bacterial
Berries	Bacterial and fungal
Broadleaf trees, shrubs, vines	Moderately fungal
Coniferous trees	Highly fungal

You can also manipulate your compost tea to be more bacterial or fungal by adding specific ingredients to feed the microbes in your brew.

Ingredient	Feeds
Blackstrap molasses	Bacteria
Maple syrup	Bacteria
White sugar	Bacteria
Cane sugar	Bacteria
Fruit juice	Bacteria
Fish emulsion	Bacteria
Kelp meal	Bacteria and fungi
Rock dust	Bacteria and fungi
Humic acid	Bacteria and fungi
Oats	Fungi
Fruit pulp	Fungi
Fish hydrolysate	Fungi

For most of us edible gardeners, a bacterial-dominated compost tea serves us well. It’s also the ideal type of tea for making a foliar spray, as the bacteria work to suppress foliar diseases regardless of the type of plant.

But don’t write off fungi just yet. Below the surface, mycorrhizal fungi form a symbiotic relationship with plant roots, helping them absorb nutrients and boosting their defenses against soilborne pathogens. They’re an important part of maintaining plant health and do the work we never see.

All said, a well rounded compost tea should host a diverse and thriving community of bacteria, fungi, and other microorganisms, but let’s face it: not a lot of us have the time or resources to be futzing around with compost tea.

How to Brew Compost Tea Without Your Own Compost

Even with several compost heaps happening around the yard, my compost never goes very far. We usually sift it in spring and if we’re lucky, we’ll have enough to spread over a few small beds. The rest of the year, we’re waiting for our compost to break down before we can use it again.

Compost tea helps you get more mileage out of your compost. Even if you don’t compost, you can make compost tea!

Disclosure: If you shop from my article or make a purchase through one of my links, I may receive commissions on some of the products I recommend.

A few months ago, Boogie Brew sent me a box of samples from their product line to try, and I’ve been using their compost tea all season long with impressive results.

My fruit trees are exploding with citrus and my herb beds are lush and green. My broccoli plants, 18 months and going on strong, are still sprouting delicious greens with not a single pest in sight. Dozens of seedlings went from my windowsill to my raised bed in only a week without any transplant shock.

The simplicity of the whole process makes it possible to brew a new batch of compost tea every week with very little effort.

Rather than concocting your own recipe, you can use Boogie Brew’s Heavy Harvest formula, which they bill as a “superb soil vitalizer and biological tonic.” The founder, Josh Cunnings, knows his stuff. He can talk soil biology all day long and truthfully, most of it goes over my head but there’s no denying his knowledge and passion for the subject.

There are three things I especially like about Boogie Brew.

One, it’s a Northern California company run by Josh and his wife out of a small warehouse. They’re a homegrown business dedicated to helping home gardeners.

Two, they supply many a marijuana grower and thus their focus is maximizing plant growth and flower production. Lots of flowers, whether on weed or on tomatoes, are a good thing!

And three, they put together a Boogie Brew Compost Tea Kit containing everything you need to successfully brew your own compost tea.

The star of the Brew Kit is Boogie Brew Tea, a fermented blend of premium biodynamic humus, high-chitinase quality worm castings, rock phosphate, langbeneite, kelp, soy and alfalfa meals, North Atlantic kelp extract, nutritional yeast, organic trace sea minerals and volcanic rock powder, humic acid (95 percent purity) from leonardite shale, and organic evaporated cane juice crystals.

It’s a balanced blend of high quality fertilizers and soil conditioners, and Josh personally sources all of the ingredients from trusted suppliers in the United States.

You can further fortify the Boogie Brew Tea with other nutrients, like Boogie Black (an insect frass fertilizer derived from black soldier fly larvae), but the original formula is a powerhouse on its own.

Dechlorinate Your Water

Before you start brewing your tea and showering your garden, it’s worth noting that if you use a municipal water source, you likely have chlorine in your water. It’s added to kill bacteria and keep the water clean, but this means it also kills good bacteria.

Always use dechlorinated water when brewing compost tea. I take it a step further and use dechlorinated water to drench my soil. After all, if I’m adding all these beneficial microbes to the soil, I certainly don’t want to kill them when I irrigate my garden.

I have the Boogie Blue Water Filter attached to three of the taps in my garden, so that all my hose water and drip irrigation water is dechlorinated. The water filter is included in this bundle with their Boogie Black and I highly recommend it.

Start Brewing

To make actively aerated compost tea (AACT), you’ll need a 5-gallon bucket, a commercial-grade air pump (with an output of at least 45 liters per minute) with a set of air stones, and Boogie Brew Tea. You’ll also need an outlet where you can run your pump overnight out of direct sunlight.

Start with a clean bucket; you don’t want any debris or old bacteria lingering in it. Fill it a couple of inches from the top with dechlorinated water.

Every bag of Boogie Brew Tea comes with a reusable burlap sack. Place one of the air stones into the sack, then add a cup of Boogie Brew Tea and cinch the sack tight.

Place the other air stone in the bucket of water and turn on the pump. Drop the burlap sack into the water and let it bubble away.

(You’ll notice that I hang my sack from a small hook on the wall. This isn’t necessary but since I don’t strain my tea, I find that it helps keep the larger particulates from escaping while the tea is aerating.)

Aerate the compost tea for 12 to 24 hours for maximum microbial activity. It’s normal for foam to collect on the surface as the compost tea is bubbling.

The optimal temperature for brewing is between 68°F and 70°F, which means you may need to brew your tea indoors if it’s especially cold or hot out.

The next day, preferably in the early morning or late afternoon when the sun is off your plants, turn off the pump and remove the burlap sack and stones.

The compost tea should smell fresh and earthy, like a forest floor. If it smells off (a sign of your compost going anaerobic), discard it and start again.

At this point you have an active, living, breathing thing in that bucket, so it’s best to use the compost tea immediately. Never let it stagnate for more than four hours (less if it’s very warm) and never try to store unused tea.

How to Use Your Compost Tea

Compost tea can be applied as a soil drench or foliar spray at a dilution rate of 1:5 to 1:10, compost tea to dechlorinated water.

The beauty of an actively aerated compost tea is that it’s impossible to overdo it the way you can with a synthetic fertilizer or even another natural fertilizer; you cannot burn the leaves with an overzealous treatment. But, you won’t necessarily reap more of the benefits by adding an entire bucket to a bed.

As a soil drench, you can pour it on the ground full-strength, especially if you’re trying to build up a new season of soil or you’ve just solarized your garden. This is ideal in spring and fall before your seeds or transplants go in the ground.

As a foliar spray, I use a 1:5 dilution for growing plants and a 1:10 dilution for seedlings. On plants that may be stressed or newly transplanted, I use a 1:1 dilution.

As you can see, there’s no standard for usage and you merely use your best judgment based on the needs of your plants. A 5-gallon bucket can go quite a long way.

With a foliar spray, it’s especially important that you shower your plants when the sun is weakest, typically before 9 am or after 3 pm. Ultraviolet rays kill microbes, even on cloudy days. I use a watering can to spray the diluted compost tea over and under the leaves.

The key to skipping the extra step of straining compost tea is using a watering can with relatively large holes, which prevent any particulates from clogging the spout (a problem I had with my previous watering can, which you can see side by side here with my current one).

It’s also suggested in the book Teaming with Microbes that a foliar spray should have a drop diameter of at least 1 millimeter, effectively allowing the bacteria to develop enough slime to establish themselves before the water evaporates.

Use the compost tea on not only your garden beds, but also your containers and even your houseplants, every two to three weeks. If you’re feeling especially motivated, you can even apply the compost tea to your plants once a week to get them going.

Once you’ve emptied the bucket, scrub it clean to remove any biofilm clinging to the surfaces; same goes for the air stones and hoses.

Toss any remaining compost in the burlap sack onto your soil, then rinse it with water and dry in the sun. A successful brew always begins and ends with clean equipment.

Compost Tea Brewing Sources

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