A shrub, while being a bushy plant, is also a non-alcoholic syrup made of concentrated fruit juice, cider vinegar and aromatics. Served in cold sparkling water, it could be thought of as a more mature cordial. 

This watermelon and basil shrub is the taste of a Southern Italian summer - slices of roadside watermelon, the smell of fresh basil lilting through the mediterranean air - all in a drink. Bottoms up!