June Blog 2026

Brew Your Way to a Healthier Garden

Everything You Need to Know About Compost Tea

If you've spent any time around serious gardeners, you've probably heard someone mention compost tea. Maybe it sounded a little mysterious, or maybe you thought it was just another gardening trend. But compost tea has been around for decades, and when brewed right, it's one of the most powerful and affordable things you can do for your garden. We're going to break it all down for you today; what it is, why it works, and how to make it at home without any expensive equipment.

What Exactly Is Compost Tea?

Think of compost tea as a probiotic smoothie for your soil. You take finished compost, the good stuff, teeming with beneficial microorganisms, steep it in water, and then aerate it to multiply those microbes into the billions. What you end up with is a liquid packed with bacteria, fungi, protozoa, and nematodes that you can apply directly to your soil or spray right onto your plant leaves.

It's not the same as simply watering with compost runoff. Properly brewed compost tea actively multiplies the living biology in your compost, giving you far more microbial activity per gallon than you'd ever get from top-dressing alone.

The Benefits for Home Gardeners

Here's why home gardeners who start brewing compost tea tend to stick with it:

Feeds your soil biology, not just your plants. Most fertilizers feed the plant directly. Compost tea feeds the microscopic ecosystem in your soil; the bacteria, fungi, and other organisms that break down nutrients and deliver them to plant roots. Healthy soil biology means healthier plants over the long run.

Improves soil structure. Microbial activity creates aggregated soil particles, tiny clusters that hold both water and air better than compacted soil. Over one to two seasons of regular compost tea applications, you'll notice your soil becoming looser, draining better, and retaining moisture longer.

Suppresses disease naturally. Beneficial microbes compete with harmful pathogens for space and resources on plant roots and leaves. A foliar spray of compost tea can help suppress common fungal diseases like powdery mildew and early blight. Research published in 2024 even showed compost tea outperforming fungicide alone in managing downy mildew on grapevines during a particularly wet season.

Reduces your need for synthetic fertilizers. As your soil biology improves, plants become more efficient at pulling nutrients from the soil. Many gardeners find they can significantly reduce, or even eliminate, synthetic fertilizer use over time.

It's incredibly affordable. If you're already composting, the main ingredient is free. A basic aeration setup costs under $20 and lasts for years.

Aerated vs. Non-Aerated Tea

There are two ways to brew compost tea, and they produce meaningfully different results.

Non-Aerated (Passive) Tea

You simply steep compost in water for 24 to 48 hours without any aeration. This produces a bacterially dominant brew that's decent for vegetables and lawns. It's easy and requires no equipment, but microbial populations are lower and the brew can turn anaerobic — meaning it starts to smell bad and can actually harm plants. If you go this route, use it quickly and make sure it smells earthy, not sour or foul.

Aerated Compost Tea (ACT)

This is the gold standard. Using a small aquarium air pump, the kind you can find at any pet store for a few dollars, you bubble oxygen through the brew continuously for 24 to 36 hours. The oxygen keeps conditions aerobic, which is exactly what beneficial microbes love. Populations explode. You get a richer, more diverse brew with far more biology than passive steeping. This is what most serious gardeners use, and it's what we'd recommend.

A good ACT brew should smell sweet and earthy, like fresh forest floor after rain. If it smells sour, sulfurous, or just plain bad, something went wrong and you should discard it and start over.

Bacterial Dominant vs Fungal Dominant…And Why It Matters

This is where compost tea gets really interesting, and where you can start tailoring your brews to your specific plants.

Your soil is home to a complex community of microorganisms, and different plants evolved alongside different balances of bacteria and fungi. Matching your brew to your plants makes a noticeable difference.

Bacterial-Dominant Tea

Best for: vegetables, herbs, annual flowers, grasses, and lawns.

Bacterial-dominant teas speed up nitrogen cycling in the soil, support insect resistance, and make an excellent foliar spray because bacteria actively suppress leaf diseases regardless of plant type. Most edible gardeners will find a bacterial-dominant brew covers the majority of their needs.

How to brew it: Use nitrogen-rich compost materials, vegetable scraps, grass clippings, manure-based compost, or worm castings fed primarily on kitchen scraps. Add a tablespoon or two of unsulfured molasses per five gallons as a bacterial food source. Brew for 24 to 36 hours with strong aeration.

Fungal-Dominant Tea

Best for: trees, shrubs, perennials, blueberries, grapes, and other acid-loving plants.

Fungal-dominant teas accelerate decomposition of tougher materials, help fight powdery mildew and downy mildew, and support mycorrhizal fungi, the underground network that connects plant roots to nutrients in ways we're still discovering. Trees and shrubs evolved in forested environments where fungi dominate, so a fungal brew feels like home to them.

How to brew it: Use carbon-rich base materials, leaf mold, wood chip compost, straw-based compost, or aged bark. Add kelp meal or fish hydrolysate (one to two tablespoons per five gallons) instead of molasses, fungi prefer complex carbohydrates over simple sugars. Brew slightly longer, up to 36 to 48 hours, and apply during cooler evening hours when soil temperatures are lower.

Balanced Tea

Best for: berry plants (except blueberries), mixed garden beds, or when you're not sure what you need.

A 50/50 blend of green and brown compost materials gives you a well-rounded brew with diverse microbial activity. When in doubt, a balanced tea is rarely the wrong call.

The Best Materials for Your Brew

The quality of your compost tea is only as good as the compost you start with. Here's a quick guide to materials and what they bring to the brew:

•        Worm castings (vermicompost) - Arguably the best base material. Packed with diverse microbial life, gentle on plants, and great for either bacterial or fungal dominance depending on what you fed your worms.

•        Finished garden compost - Solid all-purpose base. A 50/50 blend of your homemade compost and a quality finished compost from a local supplier often outperforms either alone.

•        Leaf mold - Excellent for fungal-dominant brews. Leaves decompose slowly via fungal action, so leaf mold carries a naturally fungal population.

•        Wood chip or bark compost - Strong fungal base, great for trees and shrubs.

•        Manure-based compost - High bacterial activity. Use only well-finished manure compost, never fresh.

•        Alfalfa meal - Adds nitrogen and growth stimulants. Excellent bacterial food source.

•        Kelp meal - Adds trace minerals and amino acids that fungi love. Also great for heat-stressed plants.

•        Molasses (1-2 tbsp per 5 gallons) - Bacterial food source. Easy to find at most grocery stores. Don't overdo it, too much causes anaerobic conditions.

One Thing Most People Get Wrong: The Water

Chlorinated tap water kills the microbes you're trying to cultivate. This is one of the most common mistakes new brewers make.

You have a few easy options: let tap water sit uncovered for 24 hours before brewing so the chlorine dissipates naturally, use collected rainwater or pick up a simple dechlorinating drop at any aquarium supply store, they're cheap and work instantly. Avoid well water with high iron content, which can stain plants if you're doing foliar sprays.

How and When to Apply

Apply compost tea within four hours of finishing the brew, once you stop aerating, the microbial population begins to decline.

Soil drench: Apply directly to the root zone at a rate of one to two gallons per 100 square feet. Morning application is ideal so excess moisture evaporates through the day.

Foliar spray: Use a pump sprayer and apply to both sides of leaves, ideally in the early morning or evening. Avoid midday application in hot weather. Bacterial-dominant tea works best for foliar use regardless of plant type.

Frequency: Every two to four weeks during the growing season is a solid rhythm for most home gardens. Your soil biology builds over time, so the longer you commit to it, the better the results.

How to Use Compost Tea as a Foliar Spray

Foliar spraying is one of the most effective ways to use compost tea. It gets beneficial microbes directly onto the leaf surface where they compete with disease-causing pathogens and help the plant absorb nutrients through its leaves. But there are a few important things to get right, starting with dilution.

Dilution Ratios

Never spray compost tea at full strength on leaves, the concentration can overwhelm delicate foliage and may cause burning, especially in warm weather. Here are the ratios to follow:

•        General use (established plants): 1 part compost tea to 10 parts water (1:10). This is the standard starting point for most vegetables, herbs, and flowering plants.

•        Seedlings or sensitive plants: 1:20 or even 1:30. Young plants and anything with thin or delicate leaves appreciates a gentler application. When in doubt, go lighter.

•        Trees, shrubs, and established perennials: 1:5 to 1:10. Hardier plants can handle a slightly stronger dilution, especially when targeting disease pressure.

Tips for Best Results

•        Strain before you spray. Pour your brew through cheesecloth or a fine mesh strainer before it goes into the sprayer. Even small compost particles will clog your nozzle mid-spray, straining takes 30 seconds and saves a lot of frustration.

•        Spray early morning or evening. Microbes are sensitive to UV light and heat. Morning is ideal, leaves dry through the day which prevents fungal issues, and the microbes have time to establish before the sun is at full strength. Avoid midday application in summer entirely.

•        Cover both sides of the leaves. Most pests and fungal spores take hold on the undersides of leaves first. Spray until the leaf surface glistens but isn’t dripping, you want coverage, not runoff.

•        Use it immediately once diluted. Full-strength brew has a short window of about four hours after aeration stops. Once you dilute it with water, that window shortens further. Mix only what you’ll use in one session and don’t store diluted tea.

•        Rinse your sprayer after use. Any organic residue left in the sprayer will go anaerobic quickly. A quick rinse with clean water after each use keeps your equipment clean and ready for next time.

Seasonal Brews

Adjust your brews as the seasons change. In spring, boost nitrogen content to support vigorous new growth. During summer heat, extend your brew time slightly and add kelp meal for heat stress support. In fall, shift toward a more fungal-dominant brew to help perennials and trees prepare for dormancy.

Ready to Give It a Try?

Compost tea brewing doesn't require a big investment or a lot of space; just a five-gallon bucket, an aquarium pump, some good compost, and a  little patience. Once you start seeing the difference in your soil and your plants, it becomes one of those things you wonder how you ever gardened without.

Come by on 6/20 for our Compost/Compost Tea clinic, it is free to attend, and we will be in the shade. If you can’t make the clinic that’s ok, come by anytime and we will be happy to give you all the advice you need to feel confident in your Compost Tea brewing experience. Happy brewing!