Odds are you've spotted shrubs (the vinegar-spiked drink, not the plant) on a cocktail menu or on the shelves in bottle form. If you haven't yet given them a whirl, the time is now: There are more varieties than ever taking advantage of summer's plentiful produce, and shrubs are particularly refreshing in the heat.

Shrub sherpa Michael Dietsch, author of the forthcoming book Shrubs: An Old Fashioned Drink for Modern Times (Countryman Press, $24.99), gave us the lowdown on all things shrubs—and in turn, we made his raspberry-thyme shrub, a perfectly floral and tart concoction that can be topped with soda water and gin for a late summer cocktail.

Tasting Table: What exactly is a shrub?
Michael Dietsch: A shrub is an acidulated beverage, which means it's a drink made with an acidic ingredient, like vinegar. Historically, it was a way of taking perishable fruit and preserving its shelf life. It's similar to a jam or a preserve in that regard—except it's drinkable.

TT: What does the word shrub mean, anyhow?
MD: Shrub comes from Arabic word sharab, which means "a drink" or "to drink."

TT: Okay, so we're into the idea of drinking vinegar. What's the best way to use a shrub?
MD: Today shrubs are used more as culinary ingredients. You might add a shrub to tonic or seltzer water for a nice, fruity break from soda. You can also use a shrub as a cocktail ingredient. It adds structure and backbone to a drink in a way citrus doesn't.

Shrubs by Michael Dietsch | A portrait of the author

TT: Why are shrubs ideal for summer drinking?
MD: I didn't know this until someone at Slate wrote about why we drink tart things in summer, but when you drink something sharp, like a really lemony lemonade, the tartness triggers your salivary glands. So if your mouth is dry, it gets flooded with saliva, and you feel refreshed, hydrated and invigorated. That's why shrubs feel so thirst-quenching.

TT: What's the next shrub-sation?
MD: Savory shrubs are starting to take off with some bartenders. A shrub made from tomatoes is a no-brainer because it would work well in a Bloody Mary or any other cocktail where you wanted a tomato-y element. I used a beet shrub with aquavit to make a martini variation for the book and it worked really well. You can also take sweet shrubs and add other flavors for more complexity—I like the combination of blueberries and lavender or peaches and ginger.

TT: We need a shrub, like, now. Where can we get our hands on one?
MD: The Meadow in New York or Portland, Boston Shaker in Somerville or the cheese shop Stinky Bklyn carry the major brands I interviewed for my book: Tait Farms, Liber & Co. and Shrub & Co., plus up-and-coming brands like Bug Hill Farm and Shrub Drinks. To try cocktails made with shrubs in a bar or restaurant, try Distilled NY in New York, Eastern Standard in Boston or the Velvet Tango Room in Cleveland.