Compost tea is a gentle and natural plant fertilizer that’s simple to make and very affordable if you maintain a home composting system.
Once you master brewing batches of compost tea, you’ll be able to enrich your flower garden, vegetable crops, trees, shrubs, and lawn with this gentle yet nutrient-filled organic fertilizer!
You can make compost tea in two ways: Aerated or non-aerated.
- Aerated compost tea requires a pump and air rocks to “brew” the liquid. The benefit of using the aerated method is it creates the tea in a matter of a few days, which is helpful if you have a large garden or lawn to feed.
- Non-aerated compost tea needs to steep for 7-10 days, and if not given a molasses boost to feed the microbes, many will die off before the tea is complete.
What You Need
If this is your first time, you might prefer the non-aerated compost tea method, as it’s simple and straightforward to make. The result is quite similar to the Bokashi composting method.
The ingredients for compost tea include:
- Mature compost (homemade or purchased in “tea bags” or powdered form)
- Non chlorinated water (rainwater is excellent)
- Unsulphured organic molasses
Supplies to make compost tea include:
- Five-gallon bucket or large container
- Stir stick
- Strainer or nylon sock
If you’re going for the “brewed” method, then you’ll also need an aquarium pump, tubing, and air stone.
How To Make Compost Tea
Step 1. Prep Your Compost
Decide which type of compost you’ll be using to create your tea.
If you’re taking mature compost from your home composting system or opening a bag from a store, you’ll want to remove about a gallon and shove it into the nylon socks. You want the compost to have room to move inside the nylon, so don’t pack it in and instead use two or more socks.
You can also use the loose compost inside the bucket and strain it off later, but keeping it in the nylons makes it clean up faster and less messy.
For pre-made compost tea bags or powders, follow the manufacturer’s instructions on how much you need per gallon of water and ratio it up to fill a five-gallon container.
Step 2. Add Compost to Water-Filled Bucket
Place your bucket in an area away from direct sunlight.
For loose compost, dump about a gallon (a heaping shovelful is about right) in the base of your bucket and add filtered water until it reaches two inches from the rim.
If you don’t have a chlorine-removing inline water filter, you can pre-fill the bucket 24 hours before and let it sit to allow the chlorine to disperse. You can then pour off a bit and add in your loose compost.
For tea bags or powdered compost tea products, add the correct quantity to the bottom of the bucket and fill it with water.
If you are going to use molasses to feed the microbes, add two tablespoons to the bucket.
Stir the contents gently for a couple of minutes to ensure all the compost is getting wet and the molasses dissolves.
Step 3. Let the Mixture Steep
You need to let the compost tea form a deep rich brown shade and allow the majority of microbes and nutrients to leach out of the material and into the water.
To get this to happen most effectively, you need to let the mixture steep for at least a week and stir the bucket’s contents twice daily for several minutes.
By day five, you may want to add another tablespoon of molasses to keep the microbes healthy and active.
Check the color of the water after seven days. If it’s medium brown, it’s ready to go.
If the tea looks too light, keep stirring and steeping for another day or so.
Step 4. Strain Off and Use the Compost Tea
Once your compost tea is complete, you can either remove the tea bags, nylons, or other compost-holding bags or pour the bucket contents through a strainer into another bucket.
If the tea color is light to medium in color, you can use it straight or diluted with 25-50% more unchlorinated water before using it on your garden plants.
If the compost tea is very dark, you should dilute it with equal part water or with a 1-part tea to 2-part water blend before use.
The tea, even when used at every watering, doesn’t cause the salt build-up around root systems that is a common problem with synthetic fertilizers.
How Long To Brew Compost Tea
For non-aerated compost tea, you want to brew the ingredients for 7-10 days. For aerated compost tea, you’ll want to brew the mixture for about three to four days.
You are looking for medium brown color, and depending on the compost source and age, it may take a couple of days shorter or longer to achieve the right tone.
The only difference in making compost tea with an aerator is that the extra oxygen in the water, plus the agitation from the rising bubbles, increases nutrient-leaching action and microbe activity, so the compost tea finishes faster.
Brewing Mistakes To Avoid
Using fully mature compost is critical for making safe compost tea. During the processing of unfinished compost, the material has high levels of harmful bacteria that dissipate as the compost ages and beneficial microbes take over.
A trick to determine if your home compost is mature is to:
- Place some in a plastic bag. Take a sniff before sealing it up, as it should have a fresh, earthy odor.
- Close the bag, let it sit for three days, open it back up, and take another sniff.
- If it smells the same, it’s mature. If it has a foul odor, the compost is not ready for tea making.
With the “bad” microbes gone, the plant can uptake more nutrients from the soil and enjoy robust growth and vitality.
Chlorine will kill off the live microbes that make compost tea so beneficial to plants and soil. You can get unchlorinated water by using a water filter on your garden hose or by leaving tap water in an open-lid container for 24 hours.
Not using unsulfured molasses will give poor results. When mixed with compost tea, it will help to feed the microbes and keep them active while they assist in your plant’s growth.
The living microbes inside compost tea are what sets it apart from synthetic commercial plant fertilizers. As the tea penetrates the soil, these beneficial microbes spread out and surround the roots, where they feast on harmful bacteria and fungi that cause plant damage.
Many gardeners who immediately water their plants with fresh compost tea forgo this ingredient, so this step is up to you.