This is my recipe for Blackberry Tea.
Right now it is blackberry harvest season in Oregon. Your time may vary, and of course it is possible to make this with frozen berries, but it is best when they are just off the vine, so to speak.
First, gather several cups of blackberries. You won't be using them all right away, but gather some extras. Not too much extra, because you don't want them to go to waste. In Oregon, blackberries grow everywhere. Big, ripe blackberries, most often invasive Himalyan Blackberries. Picking several cups usually takes only 20 minutes. Once you get the berries home, wash them off. Pesticides, dust and exhaust, and insects can all be on your blackberries, so rinse thoroughly. Next, take a pot and fill it up with water. Set it to boil, and at or near the point of boiling, place a cup or two of fresh berries in a strainer. Put them in the hot water, and let the water boil them until they start to blanch. At this point, every thing in your kitchen should smell like blackberries, and if you spill any of the juice, everything is going to be a mess of red juice. And you will be spilling some before the operation is done. After about 10 or 15 minutes, when the juice is soaked into the water, discard the rest of the blackberries and add several bags of tea. It doesn't have to be good tea. If you have the type of bulk tea that is used for making iced tea, that is good. The point of the tea is to add some bitterness, and also caffeine. Leave the tea in for a while to really boil the caffeine out. After a few minutes, remove the heat and let the mixture cool off. After it has cooled, pour it into a large container. This should be enough tea for a while. You can try again the next day, but at that point it is also a good idea to freeze the berries. Not quite as good as fresh, but you don't want the berries turning into a soggy mess.
I don't add sugar to my mixture, or other spices or flavors. Some lemon juice, after it is cool, might be a good idea. There might also be different spices, like cinnamon that could compliment (NB: I used this word deliberately because I want to help my tea realize its self-esteem) the mixture, but to me it is just the blackberries, and tea.