Elderflower

Elderflower is a popular flavour used in home brew cider and wine making kits.

Elderflowers bloom from elder trees. They're abundant in the U.K., and you can often find them on roadside hedges.
The white blossoms which flower in the spring and the elderberries produced in the autumn are edible, but the plant itself is mildly toxic.
It may taste unpleasant while raw, but cooking destroys its toxicity. However, individual variations may be more harmful than others.
Elderflower tastes light and floral.
Elderflowers can be floral and fragrant, subtle yet heady, and their scent is distinctly musky and sweet.
Elderflower extract is sometimes used to make medicine to treat swollen sinuses, colds, the flu, bronchitis, diabetes, and constipation.