Amy Stewart's most recent book, The Drunken Botanist, explores the odd, unusual and surprisingly common plants that produce the world's greatest spirits -- it's the perfect marriage between booze and botany. Stewart shares the connection between our gardens and our cocktail glasses, some advice and some fantastic summer cocktail recipes.

Jennifer Russell: What are some of the more interesting, unusual cocktail plants you've come across?

Amy Stewart Amy Stewart (Delightful Eye Photography)

Amy Stewart: There are all kinds of interesting and unusual plants used at every stage of making a drink, and that's sort of how I structured the book. For instance, there's a huge assortment of grains, fruits, and even grasses and tubers that we use to actually produce the alcohol itself.

One of my favorites in that first category is sorghum, a gluten-free grain that is very hardy and drought-tolerant, which has made it an important food crop for people across Africa and Asia in times of famine. In Africa they make a homemade, opaque beer from the grain, and in China it's used to make a high-proof spirit called Maotai. Here in the U.S., we see it being used for gluten-free beer. If you like Ethiopian food, you may have had injera, the flatbread, made from sorghum flour. But that's just the grain.

There's also sweet sorghum, which is pressed like sugar cane to get sugar from the stalk. I love this distiller in Indiana who is making something kind of like rum from sorghum molasses, all produced by an Amish farmer up the road. If you live in the South, you have probably had sorghum syrup or sorghum molasses, which is divine. I have a recipe in the book called the Honey Drip (that's an old variety of sweet sorghum) and it really is dessert in a glass. But that's just the spirit itself.

Then we move on to the plants that get added at the distillery to change the flavor. One of my favorite unusual plants in that category is grains of paradise. Cooks already know it as a spice, but it's used in gin as well. It's a plant in the ginger family and the seeds -- those are the grains -- have a nice warm, spicy heat that might remind you of ginger. Bombay Sapphire uses grains of paradise in its formula, and you can also find it in Samuel Adams Summer Ale.

The Drunken Botanist The Drunken Botanist

One interesting side note about this plant is that it has powerful anti-inflammatory effects. It turns out that gorillas in West Africa eat a huge amount of it in the wild -- it protects their hearts from heart disease. Zookeepers were noticing all of these heart problems with their gorillas, and they realized that it was because they were missing grains of paradise in their diet. Which is not to say that you can drink gin to take care of your heart disease -- I'm afraid it doesn't work that way.

There's a third way the plants are used to make drinks, and this is what most people are thinking of when they talk about cocktail plants: the mixers and garnishes that we might add to a drink at home. One of the more unusual plants I grow for cocktails is Mexican sour gherkin cucumbers. They're not technically cucumbers, but they are a close relative, botanically speaking. They're about the size of a grape or an olive, and they have a more tart flavor than regular cucumbers do. They're very good muddled up in a gin drink, but they also make a fantastic garnish. They're very easy to grow too -- they need a trellis to climb up, but if you give them that, you will get tons of fruit and you will amaze your friends. 

JR: I love the idea of flowers in a cocktail. How do you suggest using them?

AS: Flowers are very nice as garnishes. The problem is that something as fragile as a flower tends to drown if it's floating on a drink, so I like to make a little raft for it out of a slice of citrus or cucumber. Just poke a tiny hole through the center and drop the stem through it.  

With something like scented geranium or lavender, you can get a very nice floral flavor by making a simple syrup. Just heat equal parts sugar and water until the sugar melts, then turn off the heat and add fresh leaves and flowers. Let it steep for about an hour as it cools, then strain it and use it in place of regular simple syrup or liqueur. Be sure to keep it in the refrigerator and use it quickly -- it's just sugar water, so it won't last forever. If I have a really good batch, I might add a splash of vodka as a preservative and keep it in a Mason jar in the freezer so that it last longer.

JR: Beyond the obvious mint, what unexpected herbs are especially cocktail-friendly?

Summer Peach Old-fashioned Stewart's recipe: Summer Peach Old-fashioned

AS: Floral herbs like the ones I just mentioned -- scented geranium and lavender -- are very nice because they don't really have a lot of other culinary uses. Lemon verbena is great in drinks -- it adds a nice citrus flavor without all of the acidity of citrus juice. I also like agastache, also called anise hyssop, for its mild, citrusy, licorice flavor.

But before we get beyond mint, I just want to point out that there is an authentic Cuban strain of spearmint on the market in North America right now. It's called Mojito mint and it actually comes from Havana. So if you're dedicated to mojitos, you really want to get that one. Kentucky colonel is the favorite southern variety for mint juleps. It's worth growing a pot of each and using for those drinks.

JR: That's the perfect segue to muddling. Can you explain the difference between muddling and infusion?

AS: Muddling basically just means that you're crushing up a plant in the cocktail shaker with the spirit. To be honest, that's the best way to get flavor into a drink. Lots of people want to do infused vodkas, and it is fun to do, but the flavors aren't always really stable for very long. So if you want to make a drink with cucumbers, raspberries or honeydew melon, the best way to make that drink is just to crush it straight into a cocktail shaker.

Mamani Gin & Tonic Stewart's recipe: Mamani Gin & Tonic

If you do want to do an infusion, the trick is to use a high-proof spirit like Everclear or a 45 to 50 percent ABV vodka. Don't get rock-bottom cheap vodka, but you also don't need to spend a fortune for something in a fancy bottle. Pick something in the middle of the price range. Then make sure that you do short infusions. Fresh, green herbs like basil, cilantro or lemon verbena really only need a few hours or maybe a day. Check it frequently, taste it and strain those plants out as soon as you have the flavor you want. It is not going to get better over time. Those plants tend to produce highly volatile, aromatic molecules that are just not very stable. The same goes for soft, juicy fruit like tomatoes, peaches and melons -- you really don't need a lot of time. Citrus zest, as well as spices like cinnamon and cloves, can sit in the spirit for much longer, a month or more.

Agave Piña Stewart's recipe: Agave Piña

The thing to do is to make separate infusions of each ingredient, and then play mad scientist and blend them once they are all done. That also lets you control the proportions of each flavor. For example, if you do a hot pepper infusion, that could easily overwhelm other flavors. You might decide to add only a small amount of that and more of your infused cucumber or infused basil. If you want to make that into a liqueur, the next step is to add simple syrup to taste. Mix it in slowly until you have the degree of sweetness that you want, and then put the mixture in the refrigerator and let it sit for a few days before drinking.

With all of these infusions, remember that they are not family heirlooms and they won't last forever. It's a seasonal drink, and you should drink it this season. Have a party, invite some people over and use it up. The flavors really do start to come apart after a while. Distillers use much more sophisticated means than what we have available to us at home, so just because that bottle of Chartreuse still tastes good a few years later doesn't mean that your homemade herbal liqueur will as well.

JR: What are you drinking this summer?

AS: In the summer it's all about using what's coming from the farmers market. Here are three that I love when the produce is ripe: Summer Peach Old-Fashioned, The Farmers Market and Agave Piña.

The Farmers Market Stewart's recipe: The Farmers Market
Jennifer Russell
Jennifer Russell is a founding producer at The Splendid Table. Before coming to radio, she made historical and arts and cultural programming for public television. She claims to have come out of the womb a food lover -- when other girls played house, she played restaurateur. Follow her comings and goings on Twitter: @jenejentweets.