While you’re not wrong in thinking that a shrub is a small bush, the kind of shrub we’re talking about is an acidified fruit syrup. It’s delicious in cocktails—much, much tastier than the low lying woody flora of the same name—and easy to make at home.
Before the days of refrigeration, shrubs were a means of preserving fresh fruit. A traditional, old-school shrub is made almost like an oleo saccharum syrup, but with the addition of vinegar. Most cocktail bars now, though, make shrubs much like they would any other syrup: by simmering sugar, water and fresh fruit together and adding vinegar once the syrup has cooled.
While both methods yield a shrub that is extremely versatile in both cocktails (especially effervescent Highballs) and non-alcoholic aperitifs, the traditional method makes for a much rounder, less tart shrub, while the nouveau method results in a funkier, more vinegar-forward mix. For our recipe, we used strawberries fresh from the farmers market, but any fresh berries (like blueberries or blackberries) or citrus works well.