Make Your Own
Compost Tea

01 / Understand the process

What is compost tea?

Gardeners use the name for several water-based compost preparations. Some are stirred occasionally; others are continuously aerated with a pump. Those methods create different conditions for microorganisms, so results from one preparation cannot simply be assumed for another. [4]

This guide follows a stirred, 48-hour extraction method. It is not an actively aerated brewing system. It is also different from leachate—the drainage from a compost heap or worm bin, which may have passed through unfinished material. Do not substitute that drainage for the ingredients below. [1][7]

02 / Choose an appropriate use

Before you start

PUREARTH takes a conservative approach for a home project: use this preparation only on soil around non-edible ornamental plants. Keep it away from vegetables, herbs, fruit, edible flowers, and any plant parts you plan to eat. This restriction is an editorial precaution based on the contamination concerns in the sources—not a claim that the recipe has been safety-tested. [2][4]

If the compost’s history is uncertain, skip the liquid experiment. Improving your composting process or choosing an appropriate, clearly labelled soil amendment is a more useful next step.

03 / Keep the setup simple

Gather your materials

For one small batch, set aside:

• 500 mL of mature compost, measured by volume. For this home project, choose a plant-based compost with a known production history.
• 5 L of potable water, without chlorine or chloramine. See the Hamilton water note below.
• A clean bucket of at least 10 L capacity, never used for pesticides or other hazardous chemicals.
• A fine-mesh fabric bag, a support stick, a stirring tool, and a watering can.
• Gardening gloves, a thermometer, and a note of the starting date and time.

Method adapted from NC State Extension; hygiene follows University of Vermont guidance. [1][4]

04 / The practical method

Make a small batch

These steps describe extraction, not a proven way to manufacture a disease treatment or a pathogen-free fertiliser. The non-edible, soil-only limits above apply throughout.

1. Prepare the equipment

   Clean and sanitise the bucket, bag, stirring tool, and watering can. Follow the sanitising product’s directions, including any rinsing instructions. Wash your hands after handling compost. [4]

2. Measure and suspend

   Add 5 L water to the bucket. Put 500 mL compost in the mesh bag, submerge it, and secure it to a stick across the top.

3. Choose a sheltered position

   Keep the bucket out of direct sun at 16–27°C. Exclude debris and keep children and pets away. Record the starting time.

4. Stir over 48 hours

   Stir the liquid 12 times over the next 48 hours. Do not add sugar, molasses, or other supplements. If you cannot maintain the conditions, choose direct compost use instead.

5. Remove the compost bag

   At 48 hours, lift out the bag and transfer the liquid to the clean watering can. Do not taste it or use a spray bottle.

6. Use promptly, then clean up

   Use immediately, and within four hours of finishing. Do not bottle it for later. Clean the equipment and wash your hands.

Follow the home-use restrictions above. This adaptation is not a validated safety protocol. [1]

05 / Apply thoughtfully

Use it on the soil. Keep expectations realistic.

Apply gently to soil around a small area of non-edible ornamental plants, without splashing foliage or creating runoff. Treat it as part of the watering the plants actually need, rather than adding liquid to already saturated soil. Do not pour it onto paths or into storm drains.

There is no measured N–P–K analysis for your bucket, so a fixed “feed every week” instruction would imply more certainty than the preparation allows. Do not use it to correct a suspected deficiency without checking the soil and the plant’s requirements. [3][6]

06 / Build the foundation

Often, finished compost is the better project

Using mature compost directly retains the solid organic matter that helps improve soil structure and water management. Use a suitable amount as a soil amendment or surface dressing, guided by your soil conditions and test results. Growing in pure compost, or repeatedly adding large quantities, can create nutrient or salt problems. [6]

For a Hamilton starting point, the City’s backyard composting guide explains how to manage a pile and use the finished material. Building a simple composting routine may do more for your garden than adding a brewing routine. [10]

07 / Common questions

A few things worth knowing