How to Brew Compost Tea in Just Three Easy Steps

Mixing organic compost into your garden’s soil is one of the best ways to deliver balanced nutrition to your plants - and arguably the best way to maintain soil fertility. But it does take a little time for roots to absorb all those beneficial nutrients, and for healthy improvement to show in the plants. There may be times when your plants need need a faster boost of nutrients, and when they do, it’s time to brew up a batch of healthy tea…compost tea. 

Brewing compost tea is a lot like brewing a cup of chamomile tea at bedtime. Compost tea recipes vary from ultra simple to elaborate, but in all of them the idea is the same ; leaching nutrients from the solid material in your compost pile into water that can then be sprayed directly onto plant foliage. 

The basic compost tea recipe below will set you on the path to success, but with a batch or two under your belt, you may want to experiment. We say, go for it!

STEP 1

Shovel a few pounds of finished compost into a porous cloth sack. An old pillowcase, flour sack, or similar cloth item with tightly woven material will work just fine. Serious compost tea brewers may opt for a specially-designed compost tea brewing bag with 400 micron sized pores that allows more of the nutrients, and beneficial organisms to pass through the material and into the compost tea. But an old pair of pantyhose works good, too.

STEP 2

Once you’ve filled and securely tied off the bag, set it in a 5 gallon bucket, or similar sized container. If you have a large garden with lots of needy plants, consider a larger container with a correspondingly larger compost “tea bag”. 

STEP 3

Fill the bucket with untreated rainwater. If this isn’t available, first fill the bucket with tap water and allow it to sit uncovered for a few days, then put in the bag of compost; this step allows much of the chlorine and other chemicals that are often present in tap water to evaporate away. The beneficial biodiversity in compost is sensitive to the chemicals in treated water, and the goal is to preserve as much of this as possible in your compost tea.

Many compost tea recipes suggest using a submersible aerator like the ones used in fish aquariums, while the tea brews . This isn’t absolutely necessary to brew compost tea, but it does provide additional oxygen to the hardworking aerobic bacteria in the tea. Without enough oxygen, anaerobic bacteria can sometimes steal the show and produce a bad-smelling tea that could do more harm than good to your garden. If you plan on making compost tea on a regular basis, invest in a submersible aerator - there are plenty to choose from, they aren’t that expensive, and will help ensure a successful batch of tea every time.

But if you do happen brew a smelly batch of compost tea, don’t use it on your garden plants - just discard it somewhere outdoors.

The ideal compost tea brewing temperature is around 70 degrees, but keep it somewhere between 55 and 95, and you should be fine.

And some compost tea recipes also call for adding a few tablespoons of horticultural molasses to the solution as food for aerobic bacteria. This step isn’t necessary, but if can nurture beneficial aerobic microorganisms while the tea brews. If you do add sugar or molasses, just remember to mix it in towards the end of the brewing process. Adding sugars like horticultural molasses to the tea too soon in the brewing phase, can cause those hardworking aerobic microorganisms to burn through the available nutrients too fast.

After two or three days, your compost tea should be ready to go. Simply pour the liquid into a pump sprayer, apply the solution to the tops and undersides of leaves, and stems of your plants, and smile as your garden springs back to life.