Compost Tea: How to Brew It and Use It in Your Garden

“Compost tea” sounds rather disgusting, doesn’t it? When we think of compost, very few of us would associate a well-loved beverage with the squidgy brown soil that’s made from broken-down vegetable matter. You can rest assured that this nutrient-dense drink isn’t for human consumption. It’s a rich fertilizer that’s ideal for nourishing your plants, and we’re going to teach you how to make it and use it.

What You’ll Need

1 five-gallon bucket
Chlorine-free water (rainwater or river water is ideal)
A couple of handfuls of high-quality organic compost (let’s say 2 cups)
Blackstrap molasses
Large strainer or colander
A large stick for stirring

Directions:

Pour about 2 cups’ worth of good, rich compost into your bucket.
Add the water, and use that big old stick to stir everything around until the water looks murky.
Then, if desired, add in about a tablespoon of blackstrap molasses, stirring well as you dribble it in.

Some people get high tech and use a fish tank aerator for their compost tea, but I just use a stick to slosh everything around for about an hour until it’s properly frothy.
If you have children, this is a great way to keep them occupied for a while AND make plant food in the process. Just make sure they know not to drink any of it, because ew.

*Note: If you’d rather keep things a bit tidier, you can also cram the compost into the leg of an old pair of nylons, and use it like a giant teabag in the water bucket instead. This technique does work best with an aerator, because you don’t have to stand (or sit) there dipping that manky bag in and out of the water, so there’s another option for you.

You can let the mixture rest for a couple of hours (12 at the most), and just prod at it a little bit here and there to keep the oxygen active. When you’re ready to use it, pour some of the tea through a strainer or colander into a large watering can, and then add more water to dilute it.

You’ll want to dilute this with a 10:1 ratio of water:tea for mature plants, or 20:1 water:tea ratio for seedlings and potted plants.

A Couple of Notes:

The reason why you need to use chlorine-free water here is because the chlorine that’s added to standard water systems will actually kill the very microbes you’re trying to cultivate in this extract. You WANT the good bacteria in here, and chlorine’s antibacterial properties will destroy all of that.

Also, when you fertilise your plants, trees, water, etc., try to water close to the base rather than on the leaves, unless you see evidence of insect infestation or any kind of infection or blight on the leaves themselves. In those cases, you can pour some of the compost tea into a spray bottle and spritz the leaves and stems, which can often help alleviate the issue.

We’ll cover foliar feeding in another article.

What Good Will it Do?

All KINDS of awesome, really. Feeding your plants with compost tea doesn’t just increase their nutrient density, but can improve their flavour as well.
Effects that can result from using compost tea include:

Greener, more flavourful leaves in leafy greens like chard, collards, kale, spinach, and lettuces
Larger blooms on flowers
Better-tasting vegetables
Higher yields
Enhanced root system growth, which allows the plants to better draw nutrients from the soil, as well as providing greater stability

Think of compost tea as a tasty probiotic drink for your plants. In the same way that humans thrive when they add beneficial microbes to their gut microbiome (kombucha, kefir, sauerkraut, kimchee, yoghurt, etc.), plants also need those happy microbes to help them reach their highest potential.

Compost tea helps to build a more nutrient-rich soil, which in turn feeds your plants, which then turn around and nourish you.
Added benefit: since you’re not pouring any harmful chemicals into the soil, you’re also helping to nourish the local ecosystem as a whole.
And that is excellent.

IMPORTANT:

Compost tea must be used within 36 hours of being brewed, which is why it’s best to create it in small batches. Compost tea has to be utilised while it’s aerobic: while there are plenty of oxygen molecules booping around inside it. As soon as it goes anaerobic, it can begin to ferment, and that can cause a lot more harm to your plants than good.