Compost tea is the “espresso shot” of the organic gardening world. By aerating high-quality compost in water with food sources like molasses, you multiply beneficial bacteria and fungi by the billions. However, applying this potent biological concentrate directly to your plants without dilution can be wasteful—and in some cases, too intense for young leaves.
Use our Compost Tea Calculator to determine the perfect water-to-tea ratio for foliar sprays or root drenches. We also provide the exact ingredient list to brew your batch from scratch.
Compost Tea Dilution & Recipe
• 5 tbsp Molasses (Unsulfured)
• 5 tsp Liquid Kelp
• 7.5 cups Worm Castings / Compost
How to Use the Compost Tea Calculator
- Volume of Concentrate: Enter the amount of finished tea you have brewed (e.g., a 5-gallon bucket).
- Application Method:
- Foliar Spray: Spraying the leaves to suppress disease and feed the plant through stomata. Requires higher dilution.
- Root Drench: Pouring directly into the soil. Can handle stronger concentrations.
- Desired Strength: "Standard" is best for general maintenance. Use "Weak" for seedlings and "Strong" for established, heavy feeders like tomatoes or cannabis.
Why We Built This: The "Chlorine Trap"
The "Secret Sauce" of our tool is the warning system. The #1 mistake beginners make is diluting their beautiful, living tea with fresh tap water. Tap water contains chlorine/chloramine specifically designed to kill bacteria. If you mix it with your tea, you essentially sterilize it instantly.
Our tool reminds you to use Dechlorinated Water (rainwater or tap water that has sat out for 24 hours).
Educational Guide: The Basic Recipe
While recipes vary, the biological foundation remains the same. The goal is to feed the microbes so they reproduce rapidly.
Standard 5-Gallon Recipe
- Water: 4 Gallons (Dechlorinated).
- Inoculant: 1.5 - 2 Cups of High-Quality Compost or Worm Castings (Put in a mesh bag/nylon stocking).
- Food (Bacterial): 1-2 Tbsp Unsulfured Blackstrap Molasses.
- Food (Fungal): 1 tsp Liquid Kelp or Fish Hydrolysate.
- Air: Pump air into the bucket for 24-36 hours until it smells earthy and sweet (froth on top is good!).
Foliar vs. Root Drench
Foliar Sprays cover the leaf surface with beneficial microbes that outcompete pathogens like powdery mildew. Use a 1:10 ratio (1 part tea, 10 parts water) to ensure coverage without clogging leaf pores.
Root Drenches inject life into the soil food web. A 1:5 ratio is standard, helping to cycle nutrients and improve root uptake.
Frequently Asked Questions
Q: How long does compost tea last?
A: Use it immediately! Once you turn off the air pump, the aerobic bacteria begin to die within 4-6 hours. After 24 hours, the tea may go anaerobic (bad bacteria) and become toxic to plants.
Q: My tea smells bad. Can I use it?
A: No. Good tea smells like clean earth or sweet soil. If it smells like rotten eggs, ammonia, or vomit, it has gone anaerobic. Do not put this on your plants; dump it on a pile of wood chips or far away from the garden.
Q: Can I overdose my plants?
A: It is difficult to "burn" plants with compost tea compared to chemical fertilizers, but over-watering is a real risk. This is why we recommend specific dilution ratios—to maximize the spread of biology without waterlogging your soil.
