Compost Tea
An aerated liquid extract brewed from finished compost that delivers concentrated populations of beneficial microorganisms to plant roots and leaf surfaces.
What it is
Compost tea is produced by aerating finished, high-quality compost in water for 24 - 48 hours with a food source (such as molasses) to rapidly multiply beneficial fungi and bacteria. It is a core tool of biological gardening. The resulting liquid is rich in microbial life and can be applied as a soil drench or foliar spray.
What it does
Applied to soil, compost tea inoculates the root zone with beneficial microorganisms that compete against soilborne pathogens, improve nutrient cycling, and stimulate plant immune responses. Applied to foliage, beneficial microbes colonise leaf surfaces and can outcompete and suppress early-stage fungal pathogens through competitive exclusion and antibiotic production.
When to use
Apply compost tea throughout the growing season, particularly at transplanting, during periods of high disease pressure, or when plant vigour appears low. Foliar applications are most effective in early morning so microbes can establish before the leaf surface dries. Use within 4 hours of brewing while microbial populations are at their peak.
When not to use
Do not apply poorly made or non-aerated compost tea to edible crops close to harvest, as anaerobic brews can harbour harmful bacteria. Avoid applying to dormant plants or in temperatures below 50°F when microbial activity and establishment are greatly reduced.
How to apply
- 1
Fill a bucket with 2.5 gallons of unchlorinated water (rainwater or water left to off-gas for 24 hours is ideal).
- 2
Place 1 quart of finished, mature compost in a mesh bag or old pillowcase and submerge it in the water.
- 3
Add 1 tablespoon of unsulfured molasses as a microbial food source. Insert an aquarium air pump with a bubble stone and aerate vigorously for 24 - 36 hours.
- 4
Remove the compost bag. The liquid should smell earthy and fresh, not sour or sulphurous. Use immediately.
- 5
Apply as a soil drench around root zones at 1 quart per plant, or dilute 1:5 with water and apply as a foliar spray to all leaf surfaces.
Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.