Raspberry leaves can be gathered throughout the season, but I find they are best and most fragrant in early summer. It’s fine to dry these leaves as they are, but the flavour becomes much deeper and more complex after fermentation. It’s worth the effort! It’s also likely that more nutrients become available through fermentation and that polyphenols and antioxidant concentrations increase.
Collect raspberry leaves – to fill a small 120ml jar, you’ll need about 100g of fresh leaves. I take leaves of medium size – not the coarsest but not the most tender (those are too small!). Press or gently pound the leaves until they start to look slightly moist/bruised. Make a small pile and pound them in a mortar. Roll the slightly moist leaves into small cigars and pack them as tightly as possible into the jar – leaving about a half centimeter of space under the lid. The jar should be placed outdoors in the sun during the day and brought indoors at night – if it’s cloudy or raining outside, the jar should be kept warm indoors instead.
The raspberry leaves should be in the jar for 5-7 days, releasing any gas if necessary – not much carbonation will build up. When they smell highly aromatic, unroll them and dry. Dry them in an herb dryer, on a drying rack, or on parchment paper or a similar surface. If drying on paper, flip the leaves occasionally. This can be done with other leaves like black currant and blackberry leaves. Store them in a paper bag. To prepare the tea, pour boiling water over the leaves and let steep for 3 minutes, then strain. Delicious!
Use the same technique with fireweed/willowherb leaves (Chamaenerion angustifolium), rolling the leaves individually for appearance. Pick the leaves during flowering, and you’ll have Ivan Chai! Diluting regular tea with fermented fireweed/willowherb was also a popular (and sometimes controversial) habit during poorer times in Sweden.