Compost Tea Recipe to Supercharge Your Garden and Lawn

Compost tea, compost extract. No matter what term you hang on it, it’s simply compost and water. It’s a perfect lawn and garden feed for those who want a liquid supplement for their plants and soil, those who only make small amounts of compost, or for those who may not have the physical strength to spread compost. But how one best makes compost tea is widely debated.

The liquid that drains out of the bottom of your compost pile is not compost tea. It’s called compost leachate and should never be applied to your garden plants. Compost leachate usually carries very high concentrations of salts and microbes which may be detrimental to your plants and soil. One should also note that compost tea is only organic if the source materials used in the compost are organic.

What is compost tea?

Compost tea is a liquid version of compost, made by soaking compost in water (hence, the “tea”). The idea is that fertilizing with compost tea makes makes a wide array of nutrients immediately available to plants. Many of these nutrients aren’t available in packaged NPK fertilizers. It’s also believed that the use of the microbe-rich “tea” suppresses plant disease and builds healthy soil. Regardless of the materials used in the compost, healthful bacteria are available in compost tea, that help plants use soil nutrients quickly and efficiently.

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Aerobic vs non-aerobic compost tea

There are two types of compost tea: aerobic and non-aerobic. The difference between the two is air: one has air forced into it via bubbling (aerobic), and one is simply stirred once a day (non-aerobic).

Many articles describe elaborate contraptions for making aerobic compost tea. But this simply complicates what should be a very simple process (some people want to endlessly tinker with things that don’t need to be fixed). Dozens of research papers have shown that aerobic vs non-aerobic compost tea provides no additional protection against plant disease. The additional microbes in the aerobic brew, dependent on high concentrations of oxygen, are ultimately deposited into a mostly non-aerobic medium (your soil), and the level of oxygen in the soil will not support the aerobic bacteria. The aerobic microbe population crashes almost immediately.

On the other hand, non-aerobic compost tea, loaded with microbes that flourish in soil, is simple to make, simple to use and is brilliant at making nutrients available to plants and suppressing disease. How it suppresses disease is still a bit of a mystery, but in A/B garden plot research conducted by the Rodale Institute, the benefits were clear.

But compost tea is not a magic bullet for disease suppression or fertilizing. You should also practice crop rotation in your vegetable garden, judicious pruning when necessary, top-dressing with compost, and mulching where needed.

Compost tea recipe

Tea made with this recipe can be stored for up to 6 months and can be used at any stage of your plant’s development – from seed starting through maturity. Use it as a foliar spray or soil drench 2-4 times during the season. Use heavy applications after harvesting to replenish soil microbes and to improve disease suppression. Apply at a rate of 1 gallon per square foot.

1. Fill a 5-gallon bucket 3/4 of the way full. If filling with chlorinated municipal water, let the water sit overnight so the chlorine evaporates.
2. Add 1 quart of finished, properly cured compost to the bucket of water (there’s a huge difference in microbial activity and the types of microbes in finished and unfinished compost). There is no need to wrap the compost in burlap or cheesecloth, just drop it right into the bucket. One quart in 5 gallons is a 1:20 ratio – this ratio should be observed for any size container.
3. Stir well.
4. Cover the bucket loosely to reduce evaporation – a piece of plywood is perfect. Do not seal the bucket tight, as the “good” bacteria require air to multiply.
5. Store the covered bucket in a shady place, out of direct sunlight (UV rays and high temperatures kill beneficial bacteria).
6. Stir thoroughly once per day.
7. After 10 days, the compost tea is ready to use (it can be used sooner, but the microbe count will be lower).
8. Dilute your tea at least 1:5 with fresh water before applying to plants, lawn, and soil. Undiluted tea may contain inorganic salts like magnesium sulfide, and if not diluted, these elements may damage plants. You can dilute the tea as high as 1:60 and it will still be effective.
9. Before using, strain with a cheesecloth or fine screen to remove any material which might clog your watering can or feeder (this is not necessary if you’re using a prepared mix).

A note about starters for compost tea

It’s not necessary and in fact not recommended that you add “starters” like molasses or other sugars to the tea. Sugars are the favorite growth medium for E.coli bacteria, and you can bet that your compost contains at least a small amount of this most common bacteria, especially if you use animal manures in your compost. E.coli occurs naturally but is kept under control by beneficial bacteria. If you encourage E.coli’s growth with sugars, you could be asking for real trouble, like intestinal illness or worse.

Read the “How-To Compost Tea Guide” from the Rodale Institute.