I first learned about worm casting tea last year from Mr. Petch on Plumeria Growers. I adapted his advice with some information from my local hydroponics store.
Ideally you can use rainwater to make your worm casting tea.
I use a Calcium Inhibitor and a Gard’n Gro Rainshow’r Hose Filter with Dechlorinator on my outdoor hose. In Phoenix our water is very hard and this helps reduce those components. Still, I fill a 5 gallon bucket of hose water and drop in a single channel aerator with air stone. (You can buy these at the hydroponics store OR the pet store.) I leave that on for 24 hours. Then I add one tablespoon of UNSULPHURED molasses. When that is fully dissolved, I add 4-8 cups “Worm Gold” worm castings. (In the Phoenix metro I buy them at Treeland in Mesa.) You can add these directly or suspend them in the bucket inside a mesh bag. The fine mesh bags are often sold for use when buying fruits or vegetables. (Re-useable instead of plastic bags.)
Here’s where it gets complicated – in Phoenix when it is above 95 degrees, your tea can quickly turn “bad.” I keep a close eye on it. I usually make it late at night only brewing it for a few hours. In the Winter I can brew it for the ideal 24-36 hours.
Pass the tea through fine mesh in to your pump fine dispersal system. Spray the tops and bottoms of all the leaves at sunset or before dawn. You can directly apply the tea. Take the silky worm casting solids from inside the mesh bag or in the bottom of the bucket and add them to your pots or at the base of your trees. You can’t over-do the worm castings. My research indicates they might have a negative effect at about 15%+ of soil volume. They are a WONDERFUL deterrent to white flies, which can be really bad in Phoenix. If you apply worm castings and still have white flies, just go ahead and apply some more.
White flies are the enemy of seedlings. Worm castings and worm casting tea is a fast, easy, cheap and organic solution! My seedlings that regularly get worm casting tea are monsters. Some grew to 15 inches in less than 6 months this summer!
I love products that build microbial consortiums in the soil. Kangaroots from Fox Farms (liquid), Great White or Zho (from Botanicare) – both powders. The worm casting tea delivers microbes as well as micronutrients- at a fraction of the cost!