Umeboshi are pickled ume fruits (which are a cross between an apricot and a plum), but are often referred to as a pickled plum. This popular Japanese condiment is made by soaking young ume fruits in brine with red shiso leaves, which add flavour and a pinkish red colour. These finished plums have a sweet/sour/salty flavour, although the exact flavour varies depending on the type that you buy.