How to Make Compost Tea: Simple Steeped and Aerated Methods

Compost tea is finished compost steeped in water. The water picks up soluble nutrients and some of the microbial life from the compost, and you pour it on soil or around plants as a gentle liquid feed. It is a good way to stretch a small amount of compost across many pots, and it reaches roots faster than a solid top-dressing.

There are a lot of strong claims online about compost tea curing diseases or replacing all other fertilizer. The research on those claims is mixed. What is well supported is simpler: compost tea is a mild, low-cost liquid feed that adds a little nutrition and organic matter to the soil. Approached that way, it is easy to make and worth doing.

What you need

Finished, mature compost or worm castings. It should smell earthy and contain no recognizable food scraps.
A clean bucket of about 20 liters.
A cloth bag, old pillowcase or paint strainer bag to hold the compost.
Dechlorinated water. Rainwater is ideal. Tap water can be left standing in an open bucket for 24 hours so chlorine dissipates, although this does not remove chloramine, which some cities use.
Optional: an aquarium air pump with an air stone, and a spoonful of unsulfured molasses.

Method 1: Simple steeped tea

This is the easiest version and needs no equipment.

Fill the cloth bag with about 2 liters of compost and tie it closed.
Put it in the bucket and add about 15 liters of water.
Leave it in the shade for 24 to 48 hours, stirring once or twice a day to add a little oxygen.
Lift the bag out and squeeze it. Return the spent compost to your garden or pile.
Use the liquid the same day.

Steeped tea will be the color of weak coffee. It should smell earthy, not sour.

Method 2: Aerated tea

Aerated compost tea uses a pump to bubble air through the water. The constant oxygen favors aerobic microbes and keeps the brew from turning anaerobic and smelly.

Set up the bucket with water and the air stone at the bottom. Run the pump for an hour first if you are using tap water.
Hang the compost bag in the water, or add compost loose if you plan to strain it afterward.
Add a tablespoon of unsulfured molasses as a food source for the microbes. This is optional.
Run the pump for 24 to 36 hours, keeping the bucket out of direct sun.
Remove the bag, strain if needed, and use the tea within a few hours, while it is still fresh and oxygenated.

Two compost tea methods compared side by side — Steeped tea is slower and simpler. Aerated tea needs a pump but brews in a day.

How to dilute and apply

Use	Dilution	How often
Soil drench for vegetables and flowers	Use as is, or 1 part tea to 1 part water	Every 2 to 3 weeks in the growing season
Seedlings and young transplants	1 part tea to 3–4 parts water	Every 2 weeks
Houseplants	1 part tea to 2 parts water	Once a month in spring and summer
Lawn patches	Use as is, with a watering can	Once or twice a season

Pour it around the base of plants onto moist soil rather than onto dry soil, so it soaks in instead of running off. Early morning or evening is best, out of hot sun.

Food safety rules

Compost tea is made with organic material and can grow bacteria, especially if molasses is added. To keep things safe:

Apply tea to the soil, not to the leaves of crops you will eat raw, such as lettuce, herbs or strawberries.
Stop applying to edible crops at least two weeks before harvest.
Use clean buckets and bags, and wash them well between batches.
Never use compost that contains manure from cats, dogs or humans, and avoid fresh livestock manure.
If a batch smells sour, rotten or like sewage, pour it on a part of the garden away from food crops, or onto the compost pile, and start again.

Is it better than plain compost?

Not necessarily. Solid compost adds more organic matter and feeds the soil for longer. Tea's advantages are speed and reach. It is useful for containers where you cannot dig in compost, for giving transplants a gentle start, and for spreading a small amount of compost over a bigger area.

A balanced approach is to top-dress beds with compost once or twice a year, and use tea in between for containers and hungry crops. If you need more nitrogen for leafy growth, look at other natural options too, like those in our guide to kitchen scrap fertilizers.

Common questions

Can I store compost tea? Not for long. Aerated tea is best used within four hours. Steeped tea can be kept for a day in a covered bucket in the shade, but it loses quality and may turn sour.

Can I use worm castings instead of compost? Yes, and they make an excellent tea. Use about half the amount, since castings are more concentrated.

Is the liquid from the bottom of a worm bin the same thing? No. That is leachate, liquid that drained through partly decomposed food. It can be used heavily diluted on ornamental plants, but it is not the same as tea brewed from finished castings.

Do I need molasses? No. It feeds bacteria and makes the brew more active, but it also increases the risk of the tea going sour. Skip it if you are unsure.

Compost tea is not magic, but it is a practical way to get more out of every bucket of compost you make.