Kombucha is an acidic beverage that tastes a lot like sweetened apple cider vinegar and has reputed health benefits. It is not a mushroom at all, but a gelatinous colony of yeast and bacteria. It is easy to grow--often leaving its devotees with more "mother" or starter culture, than they know what to do with. Even so, the hardest part of growing it may be finding a mother to begin your own colony. You can purchase it, but it is often possible to find someone in your local area who will be happy to give you a free starter.
Boil water and sugar together in a large pot.
Take off the heat, add tea bags, cover and steep for about 15 minutes.
Remove the teabags and pour the sweetened tea into a one-gallon glass jar.
Allow the tea to cool to body temperature, and then add the Kombucha mother to the tea in the jar with the firm, opaque side up.
Cover the jar mouth with a clean cotton cloth secured by a rubber band and store in a warm, dark place for about one week. (The ideal temperature for fermentation to take place is between 72 and 85 degrees F.)
After one week, taste the liquid. It may still be rather sweet at this stage, but becomes more acidic as it ages. If you prefer it more acid, allow it to set a day or two longer.
When the Kombucha is as acidic as you like, drain off the tea--retaining a couple of cups with the mother to start a new batch--and store in the refrigerator to prevent further fermentation.
Use the mother and leftover liquid to start a new batch following the same steps. In this way, you will have always have a batch to drink while waiting for more to reach the proper level of fermentation.